Publications
2026
Trends in Cognitive Sciences
We recently proposed a modification to an influential conceptual framework in consciousness science: Ned Block's distinction between phenomenal (P) consciousness and access (A) consciousness [1]. Instead, we proposed that there is only one type of consciousness, requiring two necessary conditions [2]. Importantly, we did not propose a new definition of consciousness; we agree with the current consensus that it is a 'subjective experience' in the here and now, or 'what it is like' from a first-person perspective. The novelty of our proposal stems from the subtle but important shift to conceptualizing consciousness as jointly requiring two conditions. Specifically, we proposed that neural representations of 'content' (e.g., perceptions, thoughts, and feelings) must (i) be formatted in a particular way, and (ii) have the potential to influence what happens next (specifically including the ability to flexibly modify one's behavior, which in adult humans also typically entails the ability to introspect and report, given certain background conditions are met). To provide a bridge between Block's P versus A framework and ours, we referred to condition 1 as establishing 'potentially phenomenal content' (P-condition) and condition 2 as providing 'minimal access' to that content (A-condition).
iScience
Motor awareness (MA) describes the conscious access we have to the details of our movements. Although sensorimotor control relies on effector-specific transformations, many studies report similar MA thresholds across effectors, suggesting a shared, abstract representation. We tested this by having participants perform the same goal-directed reaching task once with a hand-held joystick and once by leaning with the whole body (center-of-mass displacement), using veridical or randomly deviated visual feedback. We measured corrective motor responses and fitted psychometric functions to derive MA thresholds. MA did not differ between effectors in non-deviated control trials or in “converging” trials where compensation aided the reach, and thresholds correlated strongly between effectors. By contrast, in “diverging” trials with increased kinematic demand, MA relied more on effector-specific sensorimotor information. These findings support a largely effector-independent MA mechanism, consistent with motor-equivalence principles, that is flexibly reweighted toward effector-specific transformations under uncertainty, thereby linking low-level sensorimotor corrections with abstract motor representations and consolidating a gap in conceptual frameworks of the sense of agency.
Cortex
Hallucinations are significant symptoms in psychiatric and neurodegenerative diseases, that may indicate advanced disease progression or worse disease forms. They are also frequent in healthy individuals, especially elderly or bereaved. Despite their relevance, studying hallucinations in controlled laboratory conditions remains challenging given the limited procedures inducing clinically relevant hallucinations. We have previously developed a robotics-based protocol capable of inducing a specific clinically relevant hallucination, presence hallucination (PH), in both healthy individuals and patients. Using this approach, we have systematically investigated the sensitivity and intensity of PH-induction, as well as its effects on various sensory, behavioral and cognitive aspects. In the present study, we pooled individual-participant data from 25 in-house experiments (totaling 561 individuals) and conducted a Bayesian analysis to estimate effects and moderators of PH-induction. PH-induction was reliably induced with a medium effect-size, and individuals with schizotypal traits were more sensitive. Furthermore, we identified that PH-induction may not strongly depend on altered agency, but found a synergistic relationship between passivity and induced PH. Collectively these results elucidate the role of somatomotor processes in aberrant own body perceptions, advance understanding of psychosis, and provide powerful statistical priors for future studies.
psyrXiv
The formation of a subjective sense of confidence often requires the integration of signals from multiple sources of evidence. This is of particular relevance when one needs to determine with a high degree of certainty whether a multisensory stimulus is present or absent. Understanding the mechanisms underlying this ability to map evidence strength from multiple modalities into a single confidence value is therefore central to the study of metacognition. To this end, we asked healthy adults to detect the presence or absence of near-threshold stimuli that could be visual, auditory, or both, and then rate their confidence. In two pre-registered experiments (N = 48 and N = 54), audiovisual stimuli were better detected than unimodal ones, but were not associated with better metacognitive performance. Surprisingly, participants were more confident in their absence than presence judgments. To explain these results, we fitted a Bayesian evidence accumulation model in which sensory evidence is available for presence only, rendering decisions about absence dependent on counterfactual inference. The model reproduced decision patterns by assuming that a stimulus was perceived if sensory evidence from either modality exceeded a threshold (a disjunctive integration rule). In contrast, it reproduced confidence judgments by assuming that high confidence requires that the two modalities align (conjunctive for presence, disjunctive for absence). Together, these findings reveal that distinct computational mechanisms drive perception and confidence when detecting near-threshold multisensory signals.
2025
Trends in Cognitive Sciences
Progress in the scientific study of consciousness has been impeded by several fundamental controversies. One pertains to a major divide between theories: sensory versus cognitive. Here, we argue that the key to resolving this controversy is to reevaluate the conceptual distinction proposed by Block in 1995 between phenomenal consciousness (P) and access consciousness (A). We propose that P and A should not be understood as two different types of consciousness, but as two necessary conditions for consciousness. We illustrate how this conceptual shift allows making substantial progress in answering several unresolved questions, such as the neural mechanisms and functions of consciousness, and the relationship between consciousness and attention. Our proposal motivates a selective unification across these different classes of theories.
Neuroscience of Consciousness
We have a fair understanding of what contributes to our confidence when performing individual trials of a task. However, little is known regarding the factors driving more global metacognitive estimates when a task is repeated. The present study investigates the contribution of uncertainty to global performance monitoring. In two pre-registered experiments, participants performed four trials of an orientation matching task and reported their mean response and an estimated dispersion around this perceived mean as a proxy for global performance monitoring. We considered several sources of uncertainty: response-related uncertainty, related to the participants and observed in their response variability, and perceptual or attentional uncertainty related to the sensory stimulation. Our results suggest that adults can reliably estimate the mean and dispersion of their performance and use it together with stimulus-dependent uncertainty to inform their global performance monitoring. In particular, participants adequately report that their performance was worse when uncertainty was higher. However, this capacity decreases when different types of uncertainty increase jointly. We discuss these results in light of a model of confidence that reproduced our main findings. These behavioral and computational results clarify the role of uncertainty in perceptual metacognition and the relationship between local and global performance monitoring.
Nature Communications
Perception is a multi-faceted, dynamical process that can be tackled empirically through measures of stimulus detectability and confidence. We recorded stereo-electroencephalographic data of 29 participants partaking in three pre-registered experiments to assess if evidence accumulation, a form of sequential sampling of sensory evidence, can explain perception. In an immediate-response experiment, high-gamma activity from individual channels and decoded multivariate latent variables in the visual, inferior frontal, and anterior insular cortices display a correlation between the slope of their increase and reaction times. In two further experiments, this signal in the ventral visual cortex differentiates between (1) stimuli reported as seen vs. unseen in delayed detection, (2) high and low intensity stimuli during passive viewing, and (3) levels of confidence when stimuli were detected. A computational model of leaky evidence accumulation can successfully reproduce both behavioral and neural data. Overall, we show that evidence accumulation explains subjective aspects of visual perception.
Proceedings of the Annual Meeting of the Cognitive Science Society
Detecting objects in the environment, and forming a sense of confidence in these decisions typically involves multisensory processing. We sought to characterize how humans form amodal and modality-specific confidence judgments during audiovisual detection. We found that participants made more accurate detection and confidence judgments for audiovisual than unimodal stimuli. To explain these results, we extended a Bayesian evidence accumulation model to audiovisual detection and successfully reproduced both unimodal and audiovisual detection judgments. Despite being fitted to decisions and decision times alone, our model accurately reproduced modality-specific confidence. It failed, however, to account for amodal confidence, suggesting that the latter might not arise from optimal signal integration in detection contexts. Our results indicate that, in the presence of audiovisual signals, different integration rules apply for perceptual and metacognitive decisions.
Nature Communications
Evidence accumulation is a powerful mechanism to explain the temporal dynamics of decisions, as well as their metacognitive components such as confidence judgments and changes of mind. However, it is still unclear how and where in the brain evidence accumulation leads to these two metacognitive components. We report intracranial high-gamma activity in patients with epilepsy recorded while they perform a visual discrimination task and estimate their confidence level. Our results indicate an anatomical overlap between the neural correlates of evidence accumulation, confidence, and changes of mind in the pre-supplementary motor area, as well as in the orbitofrontal, inferior frontal, and insular cortices. Behavioural and electrophysiological results are reproduced with a post-decisional evidence accumulation model, and the temporal dynamics of decision-making is characterized with mouse-tracking and intracranial electrophysiology. We conclude that confidence and changes of mind result from evidence accumulation, instantiated before the decision in the pre-supplementary motor area, and after the decision in the insula.
Schizophrenia Research
Introduction: While tone-matching disturbances have been extensively documented in schizophrenia, it remains unclear if impaired tone-matching performance is solely related to early sensory dysfunction or if the ability to appropriately translate early levels of processing into behavioral responses contributes to the deficit. Using an evidence accumulation model to analyze tone-matching performance, we aim to deconstruct perceptual decision- making into its core computational components, providing a more precise characterization of tone-matching deficits in schizophrenia. Methods: Thirty (30) individuals diagnosed with schizophrenia and 30 matched healthy controls performed a task requiring discrimination between pairs of pure tones. Behavioral performance was evaluated using Bayesian mixed-effects models of accuracy and reaction times, and further decomposed via a Drift Diffusion Model (DDM) to quantify underlying decision-making parameters. Results: Individuals with schizophrenia exhibit significantly lower accuracy and prolonged reaction times relative to controls, with a diminished impact of pitch difference levels on performance. DDM analysis revealed that individuals with schizophrenia accumulate sensory evidence at a slower rate (lower drift rate) and demonstrate increased non-decision time, reflecting delays in sensory encoding and/or motor execution. No significant dif- ferences were observed in starting point bias or boundary separation. Conclusions: These findings suggest that tone-matching impairments in schizophrenia are primarily attributable to deficits in evidence accumulation and the translation of sensory information into behavioral responses. This study provides novel insights into the cognitive pathophysiology of schizophrenia and underscores the utility of computational modeling to elucidate the mechanisms underlying perceptual and decisional deficits in this population.
Comprehensive Psychiatry
Background and HypothesisWe examined the association between metacognitive performance, functioning, and quality of life (QoL) in schizophrenia using structural equation model analyses.Study DesignA sample of 249 participants was assessed for symptoms, functioning, QoL, and both objective and subjective cognitive performance. Metacognitive performance was defined as the adequation between objective and subjective measures of cognitive performance.Study ResultsOur model showed an excellent fit (CFI = 0.981; RMSEA = 0.014–0.081) and explained 53.3% of the variance in functioning and 50.3% in QoL. Metacognitive performance was not significantly associated with functioning but showed a negative association with QoL (β = -0.383, p < 0.001). Thus, a greater underestimation of one’s cognitive abilities was linked with lower QoL, potentially reflecting heightened awareness of deficits that affect well-being. Depression, also negatively associated with QoL (β = -0.359, p < 0.001), was linked to the underestimation of cognitive abilities, whereas symptom severity was associated with their overestimation (β = -0.296, p < 0.001). Complementary analyses suggest that the subjective cognition model closely mirrors that of metacognitive performance, questioning the distinctiveness of metacognition as an explanatory factor in schizophrenia outcomes.Conclusion Our findings imply that interventions that boost confidence in cognitive abilities, such as cognitive remediation, may improve QoL. Future research should investigate the causal pathways between these factors and explore the role of social cognition, often impaired in schizophrenia, as another mediator. Comprehensive treatment that addresses clinical symptoms, depression, and subjective cognition challenges appear essential to improve outcomes in schizophrenia.
Behavioral and Brain Sciences
The scope of unconscious processing has long been, and still remains, a hotly debated issue. This is driven in part by the current diversity of methods to manipulate and measure perceptual consciousness. Here, we provide ten recommendations and nine outstanding issues about designing experimental paradigms, analyzing data, and reporting the results of studies on unconscious processing. These were formed through dialogue among a group of researchers representing a range of theoretical backgrounds. We acknowledge that some of these recommendations naturally do not align with some existing approaches and are likely to change following theoretical and methodological development. Nevertheless, we hold that at this stage of the field they are instrumental in evoking a much-needed discussion about the norms of studying unconscious processes and helping researchers make more informed decisions when designing experiments. In the long run, we aim for this paper and future discussions around the outstanding issues to lead to a more convergent corpus of knowledge about the extent – and limits – of unconscious processing.
Neuroscience of Consciousness
The scope of unconscious integration is widely debated. Here, we examined this question, focusing specifically on deciphering the relations between two associatively related objects, in a set of five behavioral and electrophysiological experiments. Participants were presented with masked pairs of related and unrelated objects and were asked to judge their relatedness. When the masked pairs were visible, we found both a behavioral priming effect and a difference in the magnitude of the electrophysiological N400 component for unrelated compared with related pairs. In sharp contrast, when the pairs were invisible (validated using both subjective and objective awareness measures), no convincing evidence was found for relatedness processing: with electroencephalography, no difference in N400 amplitude nor above-chance decoding of pair relations was found in two separate experiments. Based on these results, we conclude that the data do not support unconscious relatedness processing, suggesting that consciousness might have a prominent role in enabling relational integration beyond the single object level, which is in line with leading theories of consciousness.
Psychonomic Bulletin and Review
A wave of criticisms and replication failures is currently challenging claims about the scope of unconscious perception and cognition. Such failures to find unconscious processing effects at the population level may reflect the absence of individual-level effects, or alternatively, the averaging out of individual-level effects with opposing signs. Importantly, only the first suggests that consciousness may be necessary for the tested process to take place. To arbitrate between these two possibilities, we tested previously collected data where unconscious processing effects were not found (26 effects from 470 participants), using five frequentist and Bayesian tests that are robust to individual differences in effect signs. By and large, we found no reliable evidence for unconscious effects being masked by individual differences. In contrast, when we examined 136 non-significant effects from other domains, two novel non-parametric tests did reveal effects that were hidden by opposing individual results, though as we show, some of them might be driven by design-related factors. Taken together, five analysis approaches provide strong evidence for the restricted nature of unconscious processing effects not only across participants, but also across different trials within individuals. We provide analysis code and best-practice recommendations for testing for non-directional effects.
bioRxiv
Perceptual consciousness is defined as the subjective experience associated with the processing of sensory cues from the environment. Subjective experience unfolds over time and is accompanied by a sense of confidence, yet the mechanisms underlying these two properties remain elusive. Here, we propose a computational mechanism that accounts not only for the onset of subjective experience but also its subjective duration and associated feeling of confidence. Our model assumes that a percept becomes conscious when an ongoing, leaky accumulation of sensory evidence surpasses a perceptual threshold and stops being conscious when it falls back below the threshold due to leakage. Crucially, this perceptual threshold can be lower than the decision threshold for reporting the percept. Moreover, our model derives confidence in accurately detecting sensory evidence from the maximum reached by the evidence accumulation process following stimulus onset. We conducted a preregistered study in which three distinct models of evidence accumulation were fitted to behavioral reports of detection, confidence, and subjective duration during a face detection task under temporal uncertainty. The leaky evidence accumulation model accounted for the observed behavioral data best and outperformed alternative models without leakage. In a follow-up experiment, we investigated the impact of leakage adaptation on detection and subjective duration. We found that changes in leakage induced by contextual variations of face duration influenced both detection rates and subjective duration, as predicted by our model. Altogether, our findings suggest that leaky evidence accumulation is a suitable candidate mechanism to explain qualitative aspects of subjective experience, including subjective duration and feelings of confidence.
SSRN
Predicting the outcome of one’s actions is crucial for effective behaviour. The mechanical underpinnings of this metacognitive ability are, however, poorly understood. In two preregistered experiments, we investigated the impact of visual feedback on basketball players' ability to monitor the accuracy of their free throws. Sixty basketball players performed free throws while a visual occlusion was triggered either immediately after the ball left their hands or at intervals of 200, 400, 600, or 800ms. Participants then predicted whether or not the ball was in the basket and reported their confidence level in their answer. The results indicated that the amount of visual feedback co-varied positively with the capacity to adjust confidence to predictions following successful, but not failed throws. Our results suggest the importance of distinguishing between successful and unsuccessful trials when studying multisensory integration on motor metacognition.
2024
medRxiv
Most human studies on perceptual decision-making are correlational, and few addressed the causal role of the neural markers they identify. Here, we took the opportunity offered by deep brain stimulation to study the causal role of subthalamo-cortical networks on perceptual decision-making and perceptual monitoring. To this end, we asked participants with obsessive-compulsive disorder (OCD) treated with subthalamic stimulation to detect visual stimuli and provide confidence reports while we recorded scalp electroencephalography. Following a preregistered plan, we compared behavioural and neural results between patients off-stimulation and matched healthy controls and among patients on and off-stimulation to identify the effect of subthalamic stimulation on perceptual choices and metacognitive judgments. Our results indicate that patients off-stimulation detected visual stimuli similarly to matched healthy controls but provided poorer confidence judgments indicative of a metacognitive deficit. Moreover, chronic subthalamic stimulation significantly reduced clinical symptoms, but acute stimulation changes did not impact visual detection, confidence, or corresponding event-related potentials at the scalp level. We conclude that acute changes in subthalamic stimulation are insufficient to alleviate metacognitive deficits observed in OCD.
Communications Biology
Hallucinations can occur in the healthy population, are clinically relevant and frequent symptoms in many neuropsychiatric conditions, and have been shown to mark disease progression in patients with neurodegenerative disorders where antipsychotic treatment remains challenging. Here, we combine MR-robotics capable of inducing a clinically-relevant hallucination, with real-time fMRI neurofeedback (fMRI-NF) to train healthy individuals to up-regulate a fronto-parietal brain network associated with the robotically-induced hallucination. Over three days, participants learned to modulate occurrences of and transition probabilities to this network, leading to heightened sensitivity to induced hallucinations after training. Moreover, participants who became sensitive and succeeded in fMRI-NF training, showed sustained and specific neural changes after training, characterized by increased hallucination network occurrences during induction and decreased hallucination network occurrences during a matched control condition. These data demonstrate that fMRI-NF modulates specific hallucination network dynamics and highlights the potential of fMRI-NF as a novel antipsychotic treatment in neurodegenerative disorders and schizophrenia.
eLife
Subcortical brain structures such as the basal ganglia or the thalamus are involved in regulating motor and cognitive behavior. However, their contribution to perceptual consciousness is still unclear, due to the inherent difficulties of recording subcortical neuronal activity in humans. Here, we asked neurological patients undergoing surgery for deep brain stimulation to detect weak vibrotactile stimuli applied on their hand while recording single neuron activity from the tip of a microelectrode. We isolated putative single neurons in the subthalamic nucleus and thalamus. A significant proportion of neurons modulated their activity while participants were expecting a stimulus. We isolated a subset of neurons for which we had sufficiently good behavior to contrast neuronal activity between detected and undetected stimuli. We found that the firing rate of 23% of these neurons differed between detected and undetected stimuli. Our results provide direct neurophysiological evidence of the involvement of subcortical structures in for the detection of vibrotactile stimuli, thereby calling for a less cortico-centric view of the neural correlates of consciousness.
2023
Nature Reviews Psychology
Engaging in metacognition (evaluating, controlling, and representing cognitive states) is paramount for efficient behaviour. In this Review, we examine different types of cognitive architectures that might be at play when people provide metacognitive judgements in the domains of memory and perception. Building upon this conceptual framework, we review evidence supporting and challenging domain-general metacognition. We also discuss commonalities in metacognition across domains, focusing on the influence of decisional processes on metacognitive judgements. We emphasize the challenges of isolating metacognitive processes and how these challenges influence conclusions regarding the domain generality of metacognition, including in clinical conditions that are hypothesized to have metacognitive impairments. Finally, we give an overview of ‘adecisional’ metacognition: evaluations made outside the context of a decisional process. We find no evidence for a strong form of domain generality but outline how such an architecture could be identified in future research.
Psychological Medicine
Background Inducing hallucinations under controlled experimental conditions in non-hallucinating individuals represents a novel research avenue oriented toward understanding complex hallucinatory phenomena, avoiding confounds observed in patients. Auditory-verbal hallucinations (AVH) are one of the most common and distressing psychotic symptoms, whose etiology remains largely unknown. Two prominent accounts portray AVH either as a deficit in auditory-verbal self-monitoring, or as a result of overly strong perceptual priors. Methods In order to test both theoretical models and evaluate their potential integration, we developed a robotic procedure able to induce self-monitoring perturbations (consisting of sensorimotor conflicts between poking movements and corresponding tactile feedback) and a perceptual prior associated with otherness sensations (i.e. feeling the presence of a non-existing another person). Results Here, in two independent studies, we show that this robotic procedure led to AVH-like phenomena in healthy individuals, quantified as an increase in false alarm rate in a voice detection task. Robotically-induced AVH-like sensations were further associated with delusional ideation and to both AVH accounts. Specifically, a condition with stronger sensorimotor conflicts induced more AVH-like sensations (self-monitoring), while, in the otherness-related experimental condition, there were more AVH-like sensations when participants were detecting other-voice stimuli, compared to detecting self-voice stimuli (strong-priors). Conclusions By demonstrating an experimental procedure able to induce AVH-like sensations in non-hallucinating individuals, we shed new light on AVH phenomenology, thereby integrating self-monitoring and strong-priors accounts.
Nature Communications
According to Bayesian models, both decisions and confidence are based on the same precision-weighted integration of prior expectations (priors) and incoming information (likelihoods). This assumes that priors are integrated optimally and equally in decisions and confidence, which has not been tested. In two experiments, we quantitatively assessed how priors inform both decisions and confidence. With a gamified dual-decision task we controlled the strength of priors and likelihoods to create pairs of conditions that were matched in posterior information, but differed on whether the prior or likelihood was more informative. We found that priors were underweighted in discrimination decisions, but used to a greater extent in confidence about those decisions, and this was not due to differences in processing time. With a Bayesian model we quantified the weighting parameters for the prior at both levels, and confirmed that priors are more optimally used in explicit confidence, even when underused in decisions.
Schizophrenia
An effective way to quantify metacognitive performance is to ask participants to estimate their confidence in the accuracy of their response during a cognitive task. A recent meta-analysis raised the issue that most assessments of metacognitive performance in schizophrenia spectrum disorders may be confounded with cognitive deficits, which are known to be present in this population. Therefore, it remains unclear whether the reported metacognitive deficits are metacognitive in nature or rather inherited from cognitive deficits. Arbitrating between these two possibilities requires equating task performance between experimental groups. Here, we aimed to characterize metacognitive performance among individuals with schizophrenia across three tasks (visual detection, familiarity, recollection) using a within-subject design while controlling experimentally for intra-individual task performance and statistically for between-subject task performance. In line with our hypotheses, we found no metacognitive deficit for visual detection and familiarity judgments. While we expected metacognition for recollection to be specifically impaired among individuals with schizophrenia, we found evidence in favor of an absence of a deficit in that domain also. We found no specific metacognitive deficit in schizophrenia spectrum disorder in the visual or memory domain. The clinical relevance of our findings is discussed in light of a hierarchical framework of metacognition.
Schizophrenia
A large number of behavioral studies suggest that confidence judgments are impaired in schizophrenia, motivating the search for neural correlates of an underlying metacognitive impairment. Electrophysiological studies suggest that a specific evoked response potential reflecting performance monitoring, namely the error-related negativity (ERN), is blunted in schizophrenia compared to healthy controls. However, attention has recently been drawn to a potential confound in the study of metacognition, namely that lower task-performance in schizophrenia compared to healthy controls involves a decreased index of metacognitive performance (where metacognitive performance is construed as the ability to calibrate one’s confidence relative to response correctness), independently of metacognitive abilities among patients. Here, we assessed how this confound might also apply to ERN-blunting in schizophrenia. We used an adaptive staircase procedure to titrate task-performance on a motion discrimination task in which participants (N = 14 patients and 19 controls) had to report their confidence after each trial while we recorded high density EEG. Interestingly, not only metaperceptual abilities were preserved among patients at the behavioral level, but contrary to our hypothesis, we also found no electrophysiological evidence for altered EEG markers of performance monitoring. These results bring additional evidence suggesting an unaltered ability to monitor perceptual performance on a trial by trial basis in schizophrenia.
Royal Society Open Science
One's own voice is one of the most important and most frequently heard voices. Although it is the sound we associate most with ourselves, it is perceived as strange when played back in a recording. One of the main reasons is the lack of bone conduction that is inevitably present when hearing one's own voice while speaking. The resulting discrepancy between experimental and natural self-voice stimuli has significantly impeded self-voice research, rendering it one of the least investigated aspects of self-consciousness. Accordingly, factors that contribute to self-voice perception remain largely unknown. In a series of three studies, we rectified this ecological discrepancy by augmenting experimental self-voice stimuli with bone-conducted vibrotactile stimulation that is present during natural self-voice perception. Combining voice morphing with psychophysics, we demonstrate that specifically self-other but not familiar-other voice discrimination improved for stimuli presented using bone as compared with air conduction. Furthermore, our data outline independent contributions of familiarity and acoustic processing to separating the own from another's voice: although vocal differences increased general voice discrimination, self-voices were more confused with familiar than unfamiliar voices, regardless of their acoustic similarity. Collectively, our findings show that concomitant vibrotactile stimulation improves auditory self-identification, thereby portraying self-voice as a fundamentally multi-modal construct.
Schizophrenia Research
Background. Social metacognition is still poorly understood in schizophrenia, particularly its neuropsychological basis and its impact on insight and medication adherence. We therefore quantified social metacognition as the agreement between objective and subjective mentalization and assessed its correlates in a sample of individuals with schizophrenia spectrum disorders. Methods. Participants consisted of 143 patients with schizophrenia or schizoaffective disorders who underwent a metacognitive version of a mentalization task, an extensive neuropsychological battery, and a clinical evaluation to assess their insight into illness and medication adherence. We studied potential interactions between confidence judgments and several neuropsychological and clinical variables on mentalization accuracy with mixed-effects multiple logistic regressions. Results. Confidence judgments were closely associated with mentalization accuracy, indicative of good social metacognition in this task. Working memory, visual memory, and reasoning and problem-solving were the three neuropsychological dimensions positively associated with metacognition. By contrast, the two measures of medication adherence were associated with poorer metacognition, whereas no association was found between metacognition and clinical insight. The multiple regression model showed a significant positive impact of better working memory, older age at onset, longer duration of hospitalization, and worse medication adherence on social metacognition. Conclusions. We discuss possible mechanisms underlying the apparent association between social metacognition and working memory. Adherence should be monitored when remediating social metacognition, and psychoeducation should be given to patients with a high level of awareness of their capacity to mentalize.
2022
Perspectives on Psychological Sciences
A target question for the scientific study of consciousness is how dimensions of consciousness, such as the ability to feel pain and pleasure or reflect on one’s own experience, vary in different states and animal species. Considering the tight link between consciousness and moral status, answers to these questions have implications for law and ethics. Here we point out that given this link, the scientific community studying consciousness may face implicit pressure to carry out certain research programs or interpret results in ways that justify current norms rather than challenge them. We show that because consciousness largely determines moral status, the use of nonhuman animals in the scientific study of consciousness introduces a direct conflict between scientific relevance and ethics—the more scientifically valuable an animal model is for studying consciousness, the more difficult it becomes to ethically justify compromises to its well-being for consciousness research. Finally, in light of these considerations, we call for a discussion of the immediate ethical corollaries of the body of knowledge that has accumulated and for a more explicit consideration of the role of ideology and ethics in the scientific study of consciousness.
Perspectives on Psychological Science
Despite the tangible progress in psychological and cognitive sciences over the last several years, these disciplines still trail other more mature sciences in identifying the most important questions that need to be solved. Reaching such consensus could lead to greater synergy across different laboratories, faster progress, and increased focus on solving important problems rather than pursuing isolated, niche efforts. Here, 26 researchers from the field of visual metacognition reached consensus on four long-term and two medium-term common goals. We describe the process that we followed, the goals themselves, and our plans for accomplishing these goals. If this effort proves successful within the next few years, such consensus building around common goals could be adopted more widely in psychological science.
Communications Biology
Grid cells in entorhinal cortex (EC) encode an individual’s location in space and rely on environmental cues and self-motion cues derived from the individual’s body. Body-derived signals are also primary signals for the sense of self and based on integrated sensorimotor signals (proprioceptive, tactile, visual, motor) that have been shown to enhance self-centered processing. However, it is currently unknown whether such sensorimotor signals that modulate self-centered processing impact grid cells and spatial navigation. Integrating the online manipulation of bodily signals, to modulate self-centered processing, with a spatial navigation task and an fMRI measure to detect grid cell-like representation (GCLR) in humans, we report improved performance in spatial navigation and decreased GCLR in EC. This decrease in entorhinal GCLR was associated with an increase in retrosplenial cortex activity, which was correlated with participants’ navigation performance. These data link self-centered processes during spatial navigation to entorhinal and retrosplenial activity and highlight the role of different bodily factors at play when navigating in VR.
Schizophrenia
The Sense of Agency (SoA), our sensation of control over our actions, is a fundamental mechanism for delineating the Self from the environment and others. SoA arises from implicit processing of sensorimotor signals as well as explicit higher-level judgments. Psychosis patients suffer from difficulties in the sense of control over their actions and accurate demarcation of the Self. Moreover, it is unclear if they have metacognitive insight into their aberrant abilities. In this pre-registered study, we examined SoA and its associated confidence judgments using an embodied virtual reality paradigm in psychosis patients and controls. Our results show that psychosis patients not only have a severely reduced ability for discriminating their actions but they also do not show proper metacognitive insight into this deficit. Furthermore, an exploratory analysis revealed that the SoA capacities allow for high levels of accuracy in clinical classification of psychosis. These results indicate that SoA and its metacognition are core aspects of the psychotic state and provide possible venues for understanding the underlying mechanisms of psychosis, that may be leveraged for novel clinical purposes.
Trends in Cognitive Sciences
The neural correlates supporting our perceptual experience of the world remain largely unknown. Recent studies have shown how stimulus detection and related confidence involve evidence accumulation (EA) processes similar to those involved in perceptual decision-making. Here, we propose that independently from any tasks, percepts are not static but fade in and out of consciousness according to the dynamics of a leaky evidence accumulation process (LEAP), and that confidence corresponds to the maximal evidence accumulated by this process. We discuss the implications and limitations of our proposal, assess how it may qualify as a neural correlate of consciousness, and illustrate how it brings us closer to a mechanistic understanding of phenomenal aspects of perceptual experience like intensity and duration, beyond mere detection.
Parkinsonism and related disorders
Introduction: Premonitory urges in Tourette disorder are often linked to altered somatosensory processing, which might include deficits in metacognition. We explored tactile and visual metacognitive ability in people with Tourette disorder and healthy control participants. <br> Methods: Patients with Tourrete disorder and healthy control participants completed a tactile and a visual metacognitive task. On each trial, participants did a forced choice discrimination and then rated their confidence in their decision. To quantify metacognitive ability, we used m-ratio — a bias-free measure that allows for comparisons across modalities. Correlations between severity of tics and premonitory urges with tactile metacognitive sensitivity were also performed. <br> Results: Metacognitive ability in both tactile and visual domains was comparable between adults with Tourette disorder and healthy controls. We also found no evidence for correlations between tactile metacognitive ability and severity of premonitory urges or tic severity. <br> Conclusions: Tactile and visual metacognition is not impaired in adults with Tourette disorder. These results question the role of altered tactile metacognition in pathophysiology of tic disorders.
Journal of Experimental Psychology: General
Metacognition is defined as the capacity to monitor and control one’s own cognitive processes. Recently, Carpenter and colleagues (2019) reported that metacognitive performance can be improved through adaptive training: healthy participants performed a perceptual discrimination task, and subsequently indicated confidence in their response. Metacognitive performance, defined as how much information these confidence judgments contain about the accuracy of perceptual decisions, was found to increase in a group of participants receiving monetary reward based on their confidence judgments over hundreds of trials and multiple sessions. By contrast, in a control group where only perceptual performance was incentivized, metacognitive performance remained constant across experimental sessions. We identified two possible confounds that may have led to an artificial increase in metacognitive performance, namely the absence of reward in the initial session and an inconsistency between the reward scheme and the instructions about the confidence scale. We thus conducted a preregistered conceptual replication where all sessions were rewarded and where instructions were consistent with the reward scheme. Critically, once these two confounds were corrected we found moderate evidence for an absence of metacognitive training. Our data thus suggest that previous claims about metacognitive training are premature, and calls for more research on how to train individuals to monitor their own performance.
Psychophysiology
A growing number of studies have focused on identifying cognitive processes that are modulated by interoceptive signals, particularly in relation to the respiratory or cardiac cycle. Considering the fundamental role of interoception in bodily self-consciousness, we here investigated whether interoceptive signals also impact self-voice perception. We applied an interactive, robotic paradigm associated with somatic passivity (a bodily state characterized by illusory misattribution of self-generated touches to someone else) to investigate whether somatic passivity impacts self-voice perception as a function of concurrent interoceptive signals. Participants' breathing and heartbeat signals were recorded while they performed two self-voice tasks (self-other voice discrimination and loudness perception) and while simultaneously experiencing two robotic conditions (somatic passivity condition; control condition). Our data reveal that respiration, but not cardiac activity, affects self-voice perception: participants were better at discriminating self-voice from another person’s voice during the inspiration phase of the respiration cycle. Moreover, breathing effects were prominent in participants experiencing somatic passivity and a different task with the same stimuli (i.e., judging the loudness and not identity of the voices) was unaffected by breathing. Combining interoception and voice perception with self-monitoring framework, these data extend findings on breathing-dependent changes in perception and cognition to self-related processing.
Neuroimage
The perception that someone is nearby, although nobody can be seen or heard, is called presence hallucination (PH). Being a frequent hallucination in patients with Parkinson's disease, it has been argued to be indicative of a more severe and rapidly advancing form of the disease, associated with psychosis and cognitive decline. PH may also occur in healthy individuals and has recently been experimentally induced, in a controlled manner during fMRI, using MR-compatible robotics and sensorimotor stimulation. Previous neuroimaging correlates of such robot-induced PH, based on conventional time-averaged fMRI analysis, identified altered activity in the posterior superior temporal sulcus and inferior frontal gyrus in healthy individuals. However, no link with the strength of the robot-induced PH was observed, and such activations were also associated with other sensations induced by robotic stimulation. Here we leverage recent advances in dynamic functional connectivity, which have been applied to different psychiatric conditions, to decompose fMRI data during PH-induction into a set of co-activation patterns that are tracked over time, as to characterize their occupancies, durations, and transitions. Our results reveal that, when PH is induced, the identified brain patterns significantly and selectively increase their transition probabilities towards a specific brain pattern, centred on the posterior superior temporal sulcus, angular gyrus, dorso-lateral prefrontal cortex, and middle prefrontal cortex. This change is not observed in any other control conditions, nor is it observed in association with other sensations induced by robotic stimulation. The present findings describe the neural mechanisms of PH in healthy individuals and identify a specific disruption of the dynamics of network interactions, extending previously reported network dysfunctions in psychotic patients with hallucinations to an induced robot-controlled specific hallucination in healthy individuals.
Nature Human Behaviour
Intracortical brain–machine interfaces decode motor commands from neural signals and translate them into actions, enabling movement for paralysed individuals. The subjective sense of agency associated with actions generated via intracortical brain–machine interfaces, the neural mechanisms involved and its clinical relevance are currently unknown. By experimentally manipulating the coherence between decoded motor commands and sensory feedback in a tetraplegic individual using a brain–machine interface, we provide evidence that primary motor cortex processes sensory feedback, sensorimotor conflicts and subjective states of actions generated via the brain–machine interface. Neural signals processing the sense of agency affected the proficiency of the brain–machine interface, underlining the clinical potential of the present approach. These findings show that primary motor cortex encodes information related to action and sensing, but also sensorimotor and subjective agency signals, which in turn are relevant for clinical applications of brain–machine interfaces.
2021
Schizophrenia Bulletin
Schizophrenia is a chronic and disabling mental illness characterized by a disordered sense of self. Current theories suggest that deficiencies in the sense of control over one’s actions (Sense of Agency, SoA) may underlie some of the symptoms of schizophrenia. However, it is not clear if agency deficits are a precursor or a result of psychosis. Here, we investigated full body agency using virtual reality in a cohort of 22q11 deletion syndrome participants with a genetic propensity for schizophrenia. In two experiments employing virtual reality, full body motion tracking, and online feedback, we investigated SoA in two separate domains. Our results show that participants with 22q11DS had a considerable deficit in monitoring their actions, compared to age-matched controls in both the temporal and spatial domain. This was coupled with a bias toward erroneous attribution of actions to the self. These results indicate that nonpsychotic 22q11DS participants have a domain general deficit in the conscious sensorimotor mechanisms underlying the bodily self. Our data reveal an abnormality in the SoA in a cohort with a genetic predisposition for schizophrenia, but without psychosis, providing evidence that deficits in delineation of the self may be a precursor rather than a result of the psychotic state.
Journal of Clinical Medicine
The determinants of metacognition are still poorly understood in bipolar disorders (BD). We aimed to examine the clinical determinants of metacognition, defined as the agreement between objective and subjective cognition in individuals with BD. The participants consisted of 281 patients with BD who underwent an extensive neuropsychological battery and clinical evaluation. To assess subjective cognition, participants provided a general rating of their estimated cognitive difficulties. Clinical characteristics of BD were also recorded, along with medication. We studied the potential moderation of the association between cognitive complaints and global objective cognitive performance by several clinical variables with ordinal logistic regressions. Depression and impulsivity were associated with greater cognitive complaints. The only variable that moderated the relationship between objective and subjective cognition in the global model was the prescription of antipsychotics. Patients taking antipsychotics had a poorer association between cognitive complaints and objective neuropsychological performance. This result suggests a role for dopamine in the modulation of metacognitive performance, and calls for the systematic control of antipsychotic medication in future studies documenting metacognitive deficits in severe and persistent mental disorders. Depression and impulsivity should be investigated as potential therapeutic targets for individuals with BD and cognitive complaints, before proposing an extensive neuropsychological evaluation.
Journal of Neuroscience
Previous studies have shown that self-generated stimuli in auditory, visual, and somatosensory domains are attenuated, producing decreased behavioral and neural responses compared to the same stimuli that are externally generated. Yet, whether such attenuation also occurs for higher-level cognitive functions beyond sensorimotor processing remains unknown. In this study, we assessed whether cognitive functions such as numerosity estimations are subject to attenuation in 56 healthy participants (32 women). We designed a task allowing the controlled comparison of numerosity estimations for self (active condition) and externally (passive condition) generated words. Our behavioral results showed a larger underestimation of self- compared to externally-generated words, suggesting that numerosity estimations for self-generated words are attenuated. Moreover, the linear relationship between the reported and actual number of words was stronger for self-generated words, although the ability to track errors about numerosity estimations was similar across conditions. Neuroimaging results revealed that numerosity underestimation involved increased functional connectivity between the right intraparietal sulcus and an extended network (bilateral supplementary motor area, left inferior parietal lobule and left superior temporal gyrus) when estimating the number of self vs. externally generated words. We interpret our results in light of two models of attenuation and discuss their perceptual versus cognitive origins.
Nature Communications
A fundamental scientific question concerns the neural basis of perceptual consciousness and perceptual monitoring resulting from the processing of sensory events. Although recent studies identified neurons reflecting stimulus visibility, their functional role remains unknown. Here, we show that perceptual consciousness and monitoring involve evidence accumulation. We recorded single-neuron activity in a participant with a microelectrode in the posterior parietal cortex, while they detected vibrotactile stimuli around detection threshold and provided confidence estimates. We find that detected stimuli elicited neuronal responses resembling evidence accumulation during decision-making, irrespective of motor confounds or task demands. We generalize these findings in healthy volunteers using electroencephalography. Behavioral and neural responses are reproduced with a computational model considering a stimulus as detected if accumulated evidence reaches a bound, and confidence as the distance between maximal evidence and that bound. We conclude that gradual changes in neuronal dynamics during evidence accumulation relates to perceptual consciousness and perceptual monitoring in humans.
Science Translational Medicine
Hallucinations in Parkinson’s disease (PD) are disturbing and frequent non-motor symptoms and constitute a major risk factor for psychosis and dementia. We report a robotics-based approach applying conflicting sensorimotor stimulation, enabling the induction of presence hallucinations (PHs) and the characterization of a subgroup of patients with PD with enhanced sensitivity for conflicting sensorimotor stimulation and robot-induced PH. We next identify the fronto-temporal network of PH by combining MR-compatible robotics (and sensorimotor stimulation in healthy participants) and lesion network mapping (neurological patients without PD). This PH-network was selectively disrupted in an additional and independent cohort of patients with PD, predicted the presence of symptomatic PH, and associated with cognitive decline. These robotics-neuroimaging findings extend existing sensorimotor hallucination models to PD and reveal the pathological cortical sensorimotor processes of PH in PD, potentially indicating a more severe form of PD that has been associated with psychosis and cognitive decline.
Schizophrenia Research
Sensorimotor conflicts are known to alter the perception of accompanying sensory signals, and deficits in sensory attenuation have been observed in schizophrenia. In the auditory domain, self-generated tones or voices (compared to tones or voices presented passively or with temporal delays) have been associated with changes in loudness perception and attenuated neural responses. It has been argued that for sensory signals to be attenuated, predicted and sensory consequences must have a consistent spatiotemporal relationship, between button presses and reafferent signals, via predictive sensory signaling, a process altered in schizophrenia. Here, we investigated auditory sensory attenuation for a series of morphed voices while healthy participants applied sensorimotor stimulations that had no spatiotemporal relationship to the voice stimuli and that have been shown to induce mild psychosis-like phenomena. In two independent groups of participants, we report a loudening of silent voices and found this effect only during maximal sensorimotor conflicts (versus several control conditions). Importantly, conflicting sensorimotor stimulation also induced a mild psychosis-like state in the form of somatic passivity and participants who experienced stronger passivity lacked the sensorimotor loudening effect. We argue that this conflict-related sensorimotor loudness amplification may represent a reduction of auditory self-attenuation that is lacking in participants experiencing a concomitant mild psychosis-like state. We interpret our results within the framework of the comparator model of sensorimotor control, and discuss the implications of our findings regarding passivity experiences and hallucinations in schizophrenia.
Schizophrenia Bulletin
Psychosis, characterized by hallucinations and delusions, is a common feature of psychiatric disease, especially schizophrenia. One prominent theory posits that psychosis is driven by abnormal sensorimotor predictions leading to the misattribution of self-related events. This misattribution has been linked to passivity experiences (PE), such as loss of agency and, more recently, to presence hallucinations (PH), defined as the conscious experience of the presence of an alien agent while no person is actually present. PH has been observed in schizophrenia, Parkinson’s disease, and neurological patients with brain lesions and, recently, the brain mechanisms of PH (PH-network) have been determined comprising bilateral posterior middle temporal gyrus (pMTG), inferior frontal gyrus (IFG), and ventral premotor cortex (vPMC). Given that the experience of an alien agent is a common feature of PE, we here analyzed the functional connectivity within the PH-network in psychotic patients with (N = 39) vs without PE (N = 26). We observed reduced fronto-temporal functional connectivity in patients with PE compared to patients without PE between the right pMTG and the right and left IFG of the PH-network. Moreover, when seeding from these altered regions, we observed specific alterations with brain regions commonly linked to auditory-verbal hallucinations (such as Heschl’s gyrus). The present connectivity findings within the PH-network extend the disconnection hypothesis for hallucinations to the specific case of PH and associates the PH-network with key brain regions for frequent psychotic symptoms such as auditory-verbal hallucinations, showing that PH are relevant to the study of the brain mechanisms of psychosis and PE.
Neuroscience & Biobehavioral Reviews
Metacognitive deficits are well documented in schizophrenia spectrum disorders as a decreased capacity to adjust confidence to performance in a cognitive task. Because metacognitive ability directly depends on task performance, metacognitive deficits might be driven by lower task performance among patients. To test this hypothesis, we conducted a Bayesian meta-analysis of 42 studies comparing metacognitive abilities in 1425 individuals with schizophrenia compared to 1256 matched controls. We found a global metacognitive deficit in schizophrenia (g = -0.57, 95% CrI [-0.72, -0.43]), which was driven by studies which did not control task performance (g = -0.63, 95% CrI [-0.78, -0.49]), and inconclusive among controlled-studies (g = -0.23, 95% CrI [-0.60, 0.16], BF01 = 2.2). No correlation was found between metacognitive deficit and clinical features. We provide evidence that the metacognitive deficit in schizophrenia is inflated due to non-equated task performance. Thus, efforts should be made to develop experimental protocols accounting for lower task performance in schizophrenia.
Frontiers in Human Neuroscience
In the ongoing research of the functions of consciousness, special emphasis has been put on integration of information: the ability to combine different signals into a coherent, unified one. Several theories of consciousness hold that this ability depends on – or at least goes hand in hand with – conscious processing. Yet some empirical findings have suggested otherwise, claiming that integration of information could take place even without awareness. Trying to reconcile this apparent contradiction, the “windows of integration” (WOI) hypothesis claims that conscious access enables signal processing over large integration windows. The hypothesis applies to integration windows defined either temporally, spatially, or semantically. In this review, we explain the hypothesis and re-examine it in light of new studies published since it was suggested. In line with the hypothesis, these studies provide compelling evidence for unconscious integration, but also demonstrate its limits with respect to time, space, and semantic distance. The review further highlights open questions that still need to be pursued to demonstrate the applicability of the WOI hypothesis as a guiding principle for understanding the depth and scope of unconscious processes.
2020
Journal of Psychiatry and Neuroscience
Background: Metacognition is the set of reflexive processes that allows humans to evaluate the accuracy of their mental operations. Metacognitive deficits have been described in people with schizophrenia using mostly narrative assessment, and they have been linked to several key symptoms. Methods: We assessed metacognitive performance objectively by asking people with schizophrenia or schizoaffective disorder (n = 20) and matched healthy participants (n = 21) to perform a visual discrimination task and report their confidence in their performance. Metacognitive performance was defined as the adequacy between visual discrimination performance and confidence. Results: Bayesian analyses revealed equivalent metacognitive performance in the 2 groups, despite a weaker association between confidence and trajectory tracking during task execution among people with schizophrenia. We reproduced these results using an evidence accumulation model, which showed similar decisional processes in the 2 groups. Limitations: These results from a relatively small study sample cannot be generalized to other perceptual and nonperceptual tasks. To meet this purpose, ecological tasks are needed. As well, the role of antipsychotic medication and design deserves greater attention in the future. Conclusion: We found similar decisional and metacognitive capabilities between people with schizophrenia and healthy controls in a visual discrimination task.
Neuroimage
Episodic memory (EM) is classically conceived as a memory for events, localized in space and time, and characterized by autonoetic consciousness (ANC) allowing to mentally travel back in time and subjectively relive an event. Building on recent evidence that the first-person visual co-perception of one's own body during encoding impacts EM, we used a scene recognition task in immersive virtual reality (VR) and measured how first-person body view would modulate peri-encoding resting-state fMRI, EM performance, and ANC. Specifically, we investigated the impact of body view on post-encoding functional connectivity in an a priori network of regions related either to EM or multisensory bodily processing and used these regions in a seed-to-whole brain analysis. Post-encoding connectivity between right hippocampus (rHC) and right parahippocampus (rPHC) was enhanced when participants encoded scenes while seeing their body. Moreover, the strength of connectivity between the rHC, rPHC and the neocortex displayed two main patterns with respect to body view. The connectivity with a sensorimotor fronto-parietal network, comprising primary somatosensory and primary motor cortices, correlated with ANC after - but not before - encoding, depending on body view. The opposite change of connectivity was found between rHC, rPHC and the medial parietal cortex (from being correlated with ANC before encoding to an absence of correlation after encoding), but irrespective of body view. Linking immersive VR and fMRI for the study of EM and ANC, these findings suggest that seeing one's own body during encoding impacts the brain activity related to EM formation by modulating the connectivity between the right hippocampal formation and the neocortical regions involved in the processing of multisensory bodily signals and self-consciousness.
PLOS ONE
Social cognition is dependent on the ability to extract information from human stimuli. Of those, patterns of biological motion (BM) and in particular walking patterns of other humans, are prime examples. Although most often tested in isolation, BM outside the laboratory is often associated with multisensory cues (i.e. we often hear and see someone walking) and there is evidence that vision-based judgments of BM stimuli are systematically influenced by motor signals. Furthermore, cross-modal visuo-tactile mechanisms have been shown to influence perception of bodily stimuli. Based on these observations, we here investigated if somatosensory inputs would affect visual BM perception. In two experiments, we asked healthy participants to perform a speed discrimination task on two point light walkers (PLW) presented one after the other. In the first experiment, we quantified somatosensory-visual interactions by presenting PLW together with tactile stimuli either on the participants’ forearms or feet soles. In the second experiment, we assessed the specificity of these interactions by presenting tactile stimuli either synchronously or asynchronously with upright or inverted PLW. Our results confirm that somatosensory input in the form of tactile foot stimulation influences visual BM perception. When presented with a seen walker’s footsteps, additional tactile cues enhanced sensitivity on a speed discrimination task, but only if the tactile stimuli were presented on the relevant body-part (under the feet) and when the tactile stimuli were presented synchronously with the seen footsteps of the PLW, whether upright or inverted. Based on these findings we discuss potential mechanisms of somatosensory-visual interactions in BM perception.
eNeuro
Confidence judgments are a central tool in metacognition research. In a typical task, participants first perform perceptual (first-order) decisions and then rate their confidence in these decisions. The relationship between confidence and first-order accuracy is taken as a measure of metacognitive performance. Confidence is often assumed to stem from decision-monitoring processes alone, but processes that co-occur with the first-order decision may also play a role in confidence formation. In fact, some recent studies have revealed that directly manipulating motor regions in the brain, or the time of first-order decisions relative to second-order decisions, affects confidence judgments. This finding suggests that confidence could be informed by a readout of reaction times in addition to decision-monitoring processes. To test this possibility, we assessed the contribution of response-related signals to confidence and, in particular, to metacognitive performance (i.e., a measure of the adequacy of these confidence judgments). In human volunteers, we measured the effect of making an overt (vs covert) decision, as well as the effect of pairing an action to the stimulus about which the first-order decision is made. Against our expectations, we found no differences in overall confidence or metacognitive performance when first-order responses were covert as opposed to overt. Further, actions paired to visual stimuli presented led to higher confidence ratings, but did not affect metacognitive performance. These results suggest that confidence ratings do not always incorporate motor information.
PNAS
The human capacity to compute the likelihood that a decision is correct - known as metacognition - has proven difficult to study in isolation as it usually co-occurs with decision-making. Here, we isolated post-decisional from decisional contributions to metacognition by combining a novel paradigm with multimodal imaging. Healthy volunteers reported their confidence in the accuracy of decisions they made or decisions they observed. We found better metacognitive performance for committed vs. observed decisions, indicating that committing to a decision informs confidence. Relying on concurrent electroencephalography and hemodynamic recordings, we found a common correlate of confidence following committed and observed decisions in the inferior frontal gyrus, and a dissociation in the anterior prefrontal cortex and anterior insula. We discuss these results in light of decisional and post-decisional accounts of confidence, and propose a generative model of confidence in which metacognitive performance naturally improves when evidence accumulation is constrained upon committing a decision.
Nature Human Behavior
Understanding how people rate their confidence is critical for characterizing a wide range of perceptual, memory, motor, and cognitive processes. However, progress has been slowed by the difficulty of collecting new data and the unavailability of existing data. To address this issue, we created a large database of confidence studies spanning a broad set of paradigms, participant populations, and fields of study. The data from each study are structured in a common, easy-to-use format that can be easily imported and analyzed in a variety of software packages. Each dataset is further accompanied by an explanation regarding the nature of the collected data. At the time of publication, the confidence database (available at osf.io/s46pr) contained 145 datasets with data from over 8,700 participants and almost 4 million trials. The database will remain open for new submissions indefinitely and is expected to continue to grow. This large collection of data will enable new discoveries and can serve as a blueprint for similar databases in related fields.
In: Sathian K and Ramachandran VS, (eds). Multisensory Perception: From Laboratory to Clinic. San Diego: Elsevier Inc./Academic Press
This chapter provides a review of the main clinical alterations of body representation in neurological and psychiatric diseases. First, we describe instances of altered body representations in neurological conditions, either constrained to a specific body part (e.g., personal neglect, somatoparaphenia, phantom limbs) or impacting the whole body (autoscopic phenomena, feeling of a presence). In the second part of this chapter, we present body representation disorders associated with chronic pain and psychiatric conditions including anorexia nervosa, schizophrenia, and gender dysphoria. Beyond their clinical relevance, these conditions provide valuable insights into understanding the way our body is normally represented, and the way it is consciously experienced.
2019
Cortex
While sensorimotor signals are known to modulate perception, little is known about their influence on higher-level cognitive processes. Here, we applied sensorimotor conflicts while participants performed a perceptual task followed by confidence judgments. Results showed that sensorimotor conflicts altered metacognitive monitoring by decreasing metacognitive performance. In a second experiment, we replicated this finding and extended our results by showing that sensorimotor conflicts also altered action monitoring, as measured implicitly through intentional binding. In a third experiment, we replicated the same effects on intentional binding with sensorimotor conflicts related to the hand rather than to the trunk. However, effects of hand sensorimotor conflicts on metacognitive monitoring were not significant. Taken together, our results suggest that metacognitive and action monitoring may involve endogenous, embodied processes involving sensorimotor signals which are informative regarding the state of the decider.
Cortex
Neural evidence suggests that mechanisms associated with conscious access (i.e., the ability to report on a conscious state) are "all-or-none". Upon crossing some threshold, neural signals are globally broadcast throughout the brain and allow conscious reports. However, whether subjective experience (phenomenal consciousness) is categorical (i.e., transitioning abruptly from unconscious to conscious states) or graded (i.e., characterized by multiple intermediate states) remains an open question. To address this issue, we built a series of artificial neural networks containing distinct feedback connectivity from "multisensory" to "unisensory" cortices. In line with consciousness theories, we operationalized perceptual consciousness by the presence of feedback from higher-order nodes back to unisensory nodes which allow 'neural ignition' - a rapid, non-linear boost in response putatively leading to phenomenal consciousness. When simulating how these networks responded to unisensory and multisensory inputs, we found the fastest responses for multisensory presentations associated with multisensory feedback, and the slowest responses for multisensory presentations without feedback. Most interestingly, despite being built in line with "all-or-none" models of consciousness, multisensory stimuli associated with unisensory feedback (i.e., auditory or visual), and hence consistent with unisensory phenomenology according to theories of consciousness, generated intermediate reaction times. To extend these models to human perception and performance, we conducted extensive psychophysical testing in 29 subjects who each completed 10 h of a multisensory cue-congruency task. Consistent with the modeling results, we found that reaction times to multisensory cues reported as unisensory were intermediate between those of fully aware and fully unaware cues. These results support the existence of graded forms of phenomenological consciousness that can be instantiated by simple neural networks built in line with "all-or-none" models of consciousness.
Scientific reports
Integrating objects with their context is a key step in interpreting complex visual scenes. Here, we used functional Magnetic Resonance Imaging (fMRI) while participants viewed visual scenes depicting a person performing an action with an object that was either congruent or incongruent with the scene. Univariate and multivariate analyses revealed different activity for congruent vs. incongruent scenes in the lateral occipital complex, inferior temporal cortex, parahippocampal cortex, and prefrontal cortex. Importantly, and in contrast to previous studies, these activations could not be explained by task-induced conflict. A secondary goal of this study was to examine whether processing of object-context relations could occur in the absence of awareness. We found no evidence for brain activity differentiating between congruent and incongruent invisible masked scenes, which might reflect a genuine lack of activation, or stem from the limitations of our study. Overall, our results provide novel support for the roles of parahippocampal cortex and frontal areas in conscious processing of object-context relations, which cannot be explained by either low-level differences or task demands. Yet they further suggest that brain activity is decreased by visual masking to the point of becoming undetectable with our fMRI protocol.
2018
Cerebral cortex
Interactions with the environment happen within one's peripersonal space (PPS)-the space surrounding the body. Studies in monkeys and humans have highlighted a multisensory distributed cortical network representing the PPS. However, knowledge about the temporal dynamics of PPS processing around the trunk is lacking. Here, we recorded intracranial electroencephalography (iEEG) in humans while administering tactile stimulation (T), approaching auditory stimuli (A), and the 2 combined (AT). To map PPS, tactile stimulation was delivered when the sound was far, intermediate, or close to the body. The 19% of the electrodes showed AT multisensory integration. Among those, 30% showed a PPS effect, a modulation of the response as a function of the distance between the sound and body. AT multisensory integration and PPS effects had similar spatiotemporal characteristics, with an early response (~50 ms) in the insular cortex, and later responses (~200 ms) in precentral and postcentral gyri. Superior temporal cortex showed a different response pattern with AT multisensory integration at ~100 ms without a PPS effect. These results, represent the first iEEG delineation of PPS processing in humans and show that PPS and multisensory integration happen at similar neural sites and time periods, suggesting that PPS representation is based on a spatial modulation of multisensory integration.
Cortex
Interoceptive signals, such as the heartbeat, are processed in a network of brain regions including the insular cortex. Recent studies have shown that such signals modulate perceptual and cognitive processing, and that they impact visual awareness. For example, visual stimuli presented synchronously to the heartbeat take longer to enter visual awareness than the same stimuli presented asynchronously to the heartbeat, and this is reflected in anterior insular activation. This finding demonstrated a link between the processing of interoceptive and exteroceptive signals as well as visual awareness in the insular cortex. The advantage for visual stimuli which are asynchronous to the heartbeat to enter visual consciousness may indicate a role for the anterior insula in the suppression of the sensory consequences of cardiac signals. Here, we present data from the detailed investigation of two patients with insular lesions (as well as four patients with non-insular lesions and healthy age matched controls) indicating that a lesion of the anterior insular cortex, but not of other regions, abolished this cardio-visual suppression effect. The present data provide causal evidence for the role of the anterior insula in the integration of internal interoceptive and external sensory signals for visual awareness.
The Journal of neuroscience
Human metacognition, or the capacity to introspect on one's own mental states, has been mostly characterized through confidence reports in visual tasks. A pressing question is to what extent results from visual studies generalize to other domains. Answering this question allows determining whether metacognition operates through shared, supramodal mechanisms or through idiosyncratic, modality-specific mechanisms. Here, we report three new lines of evidence for decisional and postdecisional mechanisms arguing for the supramodality of metacognition. First, metacognitive efficiency correlated among auditory, tactile, visual, and audiovisual tasks. Second, confidence in an audiovisual task was best modeled using supramodal formats based on integrated representations of auditory and visual signals. Third, confidence in correct responses involved similar electrophysiological markers for visual and audiovisual tasks that are associated with motor preparation preceding the perceptual judgment. We conclude that the supramodality of metacognition relies on supramodal confidence estimates and decisional signals that are shared across sensory modalities.SIGNIFICANCE STATEMENT Metacognitive monitoring is the capacity to access, report, and regulate one's own mental states. In perception, this allows rating our confidence in what we have seen, heard, or touched. Although metacognitive monitoring can operate on different cognitive domains, we ignore whether it involves a single supramodal mechanism common to multiple cognitive domains or modality-specific mechanisms idiosyncratic to each domain. Here, we bring evidence in favor of the supramodality hypothesis by showing that participants with high metacognitive performance in one modality are likely to perform well in other modalities. Based on computational modeling and electrophysiology, we propose that supramodality can be explained by the existence of supramodal confidence estimates and by the influence of decisional cues on confidence estimates.
La conscience des animaux
Editions QUAE
Can animals experience emotions? Do they have a life story? The INRA addressed these questions by performing a collective scientific assessment of animal consciousness. This multidisciplinary evaluation, in which a vast body of behavioral, cognitive and neurobiological studies is analyzed, tends to show the existence of conscious thought processes in animals.
2017
Scientific reports
In physics "entrainment" refers to the synchronization of two coupled oscillators with similar fundamental frequencies. In behavioral science, entrainment refers to the tendency of humans to synchronize their movements with rhythmic stimuli. Here, we asked whether human subjects performing a tapping task would entrain their tapping to an undetected auditory rhythm surreptitiously introduced in the guise of ambient background noise in the room. Subjects performed two different tasks, one in which they tapped their finger at a steady rate of their own choosing and one in which they performed a single abrupt finger tap on each trial after a delay of their own choosing. In both cases we found that subjects tended to tap in phase with the inducing modulation, with some variability in the preferred phase across subjects, consistent with prior research. In the repetitive tapping task, if the frequency of the inducing stimulus was far from the subject's own self-paced frequency, then entrainment was abolished, consistent with the properties of entrainment in physics. Thus, undetected ambient noise can influence self-generated movements. This suggests that uncued decisions to act are never completely endogenous, but are subject to subtle unnoticed influences from the sensory environment.
Cognition
Recent studies have highlighted the role of multisensory integration as a key mechanism of self-consciousness. In particular, integration of bodily signals within the peripersonal space (PPS) underlies the experience of the self in a body we own (self-identification) and that is experienced as occupying a specific location in space (self-location), two main components of bodily self-consciousness (BSC). Experiments investigating the effects of multisensory integration on BSC have typically employed supra-threshold sensory stimuli, neglecting the role of unconscious sensory signals in BSC, as tested in other consciousness research. Here, we used psychophysical techniques to test whether multisensory integration of bodily stimuli underlying BSC also occurs for multisensory inputs presented below the threshold of conscious perception. Our results indicate that visual stimuli rendered invisible through continuous flash suppression boost processing of tactile stimuli on the body (Exp. 1), and enhance the perception of near-threshold tactile stimuli (Exp. 2), only once they entered PPS. We then employed unconscious multisensory stimulation to manipulate BSC. Participants were presented with tactile stimulation on their body and with visual stimuli on a virtual body, seen at a distance, which were either visible or rendered invisible. We found that participants reported higher self-identification with the virtual body in the synchronous visuo-tactile stimulation (as compared to asynchronous stimulation; Exp. 3), and shifted their self-location toward the virtual body (Exp.4), even if stimuli were fully invisible. Our results indicate that multisensory inputs, even outside of awareness, are integrated and affect the phenomenological content of self-consciousness, grounding BSC firmly in the field of psychophysical consciousness studies.
The Blackwell Companion to Consciousness
Contrasting the properties of conscious and unconscious processes is crucial for understanding how consciousness occurs in the brain. In this chapter, we review the theoretical framework and empirical methods used to delineate and contrast conscious vs. unconscious perception. After outlining the main approaches to measure unconscious influences on brain and behavior, we describe some of the psychophysical tools employed to render stimuli unconscious, including the depletion of sensory signals, attentional resources, and vigilance states. We then provide an overview of the extent and limits of unconscious perception, and conclude on the future of the contrastive approach to the study of consciousness.
The Journal of neuroscience
Vision is known to be shaped by context, defined by environmental and bodily signals. In the Taylor illusion, the size of an afterimage projected on one's hand changes according to proprioceptive signals conveying hand position. Here, we assessed whether the Taylor illusion does not just depend on the physical hand position, but also on bodily self-consciousness as quantified through illusory hand ownership. Relying on the somatic rubber hand illusion, we manipulated hand ownership, such that participants embodied a rubber hand placed next to their own hand. We found that an afterimage projected on the participant's hand drifted depending on illusory ownership between the participants' two hands, showing an implication of self-representation during the Taylor illusion. Oscillatory power analysis of electroencephalographic signals showed that illusory hand ownership was stronger in participants with stronger alpha suppression over left sensorimotor cortex, whereas the Taylor illusion correlated with higher beta/gamma power over frontotemporal regions. Higher gamma connectivity between left sensorimotor and inferior parietal cortex was also found during illusory hand ownership. These data show that afterimage drifts in the Taylor illusion do not only depend on the physical hand position but also on subjective ownership, which itself is based on the synchrony of somatosensory signals from the two hands. The effect of ownership on afterimage drifts is associated with beta/gamma power and gamma connectivity between frontoparietal regions and the visual cortex. Together, our results suggest that visual percepts are not only influenced by bodily context but are self-grounded, mapped on a self-referential frame.
Neuroscience of consciousness
Over the last 30 years, our understanding of the neurocognitive bases of consciousness has improved, mostly through studies employing vision. While studying consciousness in the visual modality presents clear advantages, we believe that a comprehensive scientific account of subjective experience must not neglect other exteroceptive and interoceptive signals as well as the role of multisensory interactions for perceptual and self-consciousness. Here, we briefly review four distinct lines of work which converge in documenting how multisensory signals are processed across several levels and contents of consciousness. Namely, how multisensory interactions occur when consciousness is prevented because of perceptual manipulations (i.e. subliminal stimuli) or because of low vigilance states (i.e. sleep, anesthesia), how interactions between exteroceptive and interoceptive signals give rise to bodily self-consciousness, and how multisensory signals are combined to form metacognitive judgments. By describing the interactions between multisensory signals at the perceptual, cognitive, and metacognitive levels, we illustrate how stepping out the visual comfort zone may help in deriving refined accounts of consciousness, and may allow cancelling out idiosyncrasies of each sense to delineate supramodal mechanisms involved during consciousness.
2016
Neuropsychologia
The majority of scientific studies on consciousness have focused on vision, exploring the cognitive and neural mechanisms of conscious access to visual stimuli. In parallel, studies on bodily consciousness have revealed that bodily (i.e. tactile, proprioceptive, visceral, vestibular) signals are the basis for the sense of self. However, the role of bodily signals in the formation of visual consciousness is not well understood. Here we investigated how body-related visuo-tactile stimulation modulates conscious access to visual stimuli. We used a robotic platform to apply controlled tactile stimulation to the participants' back while they viewed a dot moving either in synchrony or asynchrony with the touch on their back. Critically, the dot was rendered invisible through continuous flash suppression. Manipulating the visual context by presenting the dot moving on either a body form, or a non-bodily object we show that: (i) conflict induced by synchronous visuo-tactile stimulation in a body context is associated with a delayed conscious access compared to asynchronous visuo-tactile stimulation, (ii) this effect occurs only in the context of a visual body form, and (iii) is not due to detection or response biases. The results indicate that body-related visuo-tactile conflicts impact visual consciousness by facilitating access of non-conflicting visual information to awareness, and that these are sensitive to the visual context in which they are presented, highlighting the interplay between bodily signals and visual experience.
Journal of vision
The two-thirds power law describes the relationship between velocity and curvature in human motor movements. Interestingly, this motor law also affects visual motion perception, in which stimuli moving according to the two-thirds power law are perceived to have a constant velocity compared to stimuli actually moving at constant velocity. Thus, visual motion adhering to biological motion principles causes a kinematic illusion of smooth and velocity-invariant motion. However, it is yet unclear how this motion law affects the discrimination of visual stimuli and if its encoding requires attention. Here we tested the perceptual discrimination of stimuli following biological (two-thirds power law) or nonbiological movement under conditions in which the stimuli were degraded or masked through continuous flash suppression. Additionally, we tested subjective perception of naturalness and velocity consistency. Our results show that the discriminability of a visual target is inversely related to the perceived "naturalness" of its movement. Discrimination of stimuli following the two-thirds power law required more time than the same stimuli moving at constant velocity or nonecological variants of the two-thirds power law and was present for both masked and degraded stimuli.
The Journal of neuroscience
The processing of interoceptive signals in the insular cortex is thought to underlie self-awareness. However, the influence of interoception on visual awareness and the role of the insular cortex in this process remain unclear. Here, we show in a series of experiments that the relative timing of visual stimuli with respect to the heartbeat modulates visual awareness. We used two masking techniques and show that conscious access for visual stimuli synchronous to participants' heartbeat is suppressed compared with the same stimuli presented asynchronously to their heartbeat. Two independent brain imaging experiments using high-resolution fMRI revealed that the insular cortex was sensitive to both visible and invisible cardio-visual stimulation, showing reduced activation for visual stimuli presented synchronously to the heartbeat. Our results show that interoceptive insular processing affects visual awareness, demonstrating the role of the insula in integrating interoceptive and exteroceptive signals and in the processing of conscious signals beyond self-awareness. <br><br> Significance statement: There is growing evidence that interoceptive signals conveying information regarding the internal state of the body influence perception and self-awareness. The insular cortex, which receives sensory inputs from both interoceptive and exteroceptive sources, is thought to integrate these multimodal signals. This study shows that cardiac interoceptive signals modulate awareness for visual stimuli such that visual stimuli occurring at the cardiac frequency take longer to access visual awareness and are more difficult to discriminate. Two fMRI experiments show that the insular region is sensitive to this cardio-visual synchrony even when the visual stimuli are rendered invisible through interocular masking. The results indicate a perceptual and neural suppression for visual events coinciding with cardiac interoceptive signals.
Multisensory Research
The integration of information has been considered a hallmark of human consciousness, as it requires information being globally available via widespread neural interactions. Yet the complex interdependencies between multisensory integration and perceptual awareness, or consciousness, remain to be defined. While perceptual awareness has traditionally been studied in a single sense, in recent years we have witnessed a surge of interest in the role of multisensory integration in perceptual awareness. Based on a recent IMRF symposium on multisensory awareness, this review discusses three key questions from conceptual, methodological and experimental perspectives: (1) What do we study when we study multisensory awareness? (2) What is the relationship between multisensory integration and perceptual awareness? (3) Which experimental approaches are most promising to characterize multisensory awareness? We hope that this review paper will provoke lively discussions, novel experiments, and conceptual considerations to advance our understanding of the multifaceted interplay between multisensory integration and consciousness.
Perception
Although the interaction between vision and touch is of crucial importance for perceptual and bodily self-consciousness, only little is known regarding the link between conscious access and tactile processing. Here, we tested whether the numerical encoding of tactile stimuli depends on conscious discrimination. On each trial, participants received between zero and three taps at low, medium, or high intensity and had to enumerate the number of visual items subsequently presented as a visual target. We measured tactovisual numerical priming, that is, the modulation of reaction times according to the numerical distance between the visual target and tactile prime values. While numerical priming and repetition priming were respectively elicited by high and medium intensity stimuli, no effect was found for low intensity stimuli that were not discriminable. This suggests that numerical priming between touch and vision depends on tactile discrimination. We discuss our results considering recent advances in unconscious visual numerical priming.
The Neurology of Conciousness
Out-of-body experiences (OBEs) and near-death experiences (NDEs) are complex phenomena that have fascinated mankind from time immemorial. OBEs are defined as experiences in which a person seems to be awake and sees his body and the world from a disembodied location outside his physical body. Recent neurological and neuroscientific research suggests that OBEs are the result of disturbed bodily multisensory integration, primarily in right temporo-parietal cortex. NDEs are more loosely defined, and refer to a set of subjective phenomena, often including an OBE, that are triggered by a life-threatening situation. Although a number of different theories have been proposed about the putative brain processes underlying NDEs, neurologists and cognitive neuroscientists have, so far, paid little attention to these phenomena, although several experimental investigations based on principles from cognitive neuroscience are possible. This might be understandable but is unfortunate, because the neuroscientific study of NDEs could provide insights into the functional and neural mechanisms of beliefs, concepts, personality, spirituality, magical thinking, and the self. Based on previous medical and psychological research in cardiac arrest patients with NDEs, we sketch a neurological framework for the study of the so-called NDEs.
Journal of vision
The scope and limits of unconscious processing are a matter of ongoing debate. Lately, continuous flash suppression (CFS), a technique for suppressing visual stimuli, has been widely used to demonstrate surprisingly high-level processing of invisible stimuli. Yet, recent studies showed that CFS might actually allow low-level features of the stimulus to escape suppression and be consciously perceived. The influence of such low-level awareness on high-level processing might easily go unnoticed, as studies usually only probe the visibility of the feature of interest, and not that of lower-level features. For instance, face identity is held to be processed unconsciously since subjects who fail to judge the identity of suppressed faces still show identity priming effects. Here we challenge these results, showing that such high-level priming effects are indeed induced by faces whose identity is invisible, but critically, only when a lower-level feature, such as color or location, is visible. No evidence for identity processing was found when subjects had no conscious access to any feature of the suppressed face. These results suggest that high-level processing of an image might be enabled by-or co-occur with-conscious access to some of its low-level features, even when these features are not relevant to the processed dimension. Accordingly, they call for further investigation of lower-level awareness during CFS, and reevaluation of other unconscious high-level processing findings.
2015
Current opinion in neurology
PURPOSE OF REVIEW: In recent years, consciousness has become a central topic in cognitive neuroscience. This review focuses on the relation between bodily self-consciousness - the feeling of being a subject in a body - and visual consciousness - the subjective experience associated with the perception of visual signals. <br> <br>RECENT FINDINGS: Findings from clinical and experimental work have shown that bodily self-consciousness depends on specific brain networks and is related to the integration of signals from multiple sensory modalities including vision. In addition, recent experiments have shown that visual consciousness is shaped by the body, including vestibular, tactile, proprioceptive, and motor signals. <br> <br>SUMMARY: Several lines of evidence suggest reciprocal relationships between vision and bodily signals, indicating that a comprehensive understanding of visual and bodily self-consciousness requires studying them in unison.
2014
Psychological science
Multisensory integration is thought to require conscious perception. Although previous studies have shown that an invisible stimulus could be integrated with an audible one, none have demonstrated integration of two subliminal stimuli of different modalities. Here, pairs of identical or different audiovisual target letters (the sound /b/ with the written letter "b" or "m," respectively) were preceded by pairs of masked identical or different audiovisual prime digits (the sound /6/ with the written digit "6" or "8," respectively). In three experiments, awareness of the audiovisual digit primes was manipulated, such that participants were either unaware of the visual digit, the auditory digit, or both. Priming of the semantic relations between the auditory and visual digits was found in all experiments. Moreover, a further experiment showed that unconscious multisensory integration was not obtained when participants did not undergo prior conscious training of the task. This suggests that following conscious learning, unconscious processing suffices for multisensory integration.
Trends in cognitive sciences
Information integration and consciousness are closely related, if not interdependent. But, what exactly is the nature of their relation? Which forms of integration require consciousness? Here, we examine the recent experimental literature with respect to perceptual and cognitive integration of spatiotemporal, multisensory, semantic, and novel information. We suggest that, whereas some integrative processes can occur without awareness, their scope is limited to smaller integration windows, to simpler associations, or to ones that were previously acquired consciously. This challenges previous claims that consciousness of some content is necessary for its integration; yet it also suggests that consciousness holds an enabling role in establishing integrative mechanisms that can later operate unconsciously, and in allowing wider-range integration, over bigger semantic, spatiotemporal, and sensory integration windows.
Journal of vision
Visual awareness of an event, object, or scene is, by essence, an integrated experience, whereby different visual features composing an object (e.g., orientation, color, shape) appear as an unified percept and are processed as a whole. Here, we tested in human observers whether perceptual integration of static motion cues depends on awareness by measuring the capacity to infer the direction of motion implied by a static visible or invisible image under continuous flash suppression. Using measures of directional adaptation, we found that visible but not invisible implied motion adaptors biased the perception of real motion probes. In a control experiment, we found that invisible adaptors implying motion primed the perception of subsequent probes when they were identical (i.e., repetition priming), but not when they only shared the same direction (i.e., direction priming). Furthermore, using a model of visual processing, we argue that repetition priming effects are likely to arise as early as in the primary visual cortex. We conclude that although invisible images implying motion undergo some form of nonconscious processing, visual awareness is necessary to make inferences about motion direction.
Psychological science
Can people learn complex information without conscious awareness? Implicit learning-learning without awareness of what has been learned-has been the focus of intense investigation over the last 50 years. However, it remains controversial whether complex knowledge can be learned implicitly. In the research reported here, we addressed this challenge by asking participants to differentiate between sequences of symbols they could not perceive consciously. Using an operant-conditioning task, we showed that participants learned to associate distinct sequences of crowded (nondiscriminable) symbols with their respective monetary outcomes (reward or punishment). Overall, our study demonstrates that sensitivity to sequential regularities can arise through the nonconscious temporal integration of perceptual information.
Frontiers in psychology
Cognition
In order to interpret a constantly changing environment, visual events far apart in space and time must be integrated into a unified percept. While spatial properties of invisible signals are known to be encoded without awareness, the fate of temporal properties remains largely unknown. Here, we probed temporal integration for two distinct motion stimuli that were either visible or rendered invisible using continuous flash suppression. We found that when invisible, both the direction of apparent motion and the gender of point-light walkers were processed only when defined across short time periods (i.e., respectively 100ms and 1000ms). This limitation was not observed under full visibility. These similar findings at two different hierarchical levels of processing suggest that temporal integration windows shrink in the absence of perceptual awareness. We discuss this phenomenon as a key prediction of the global neuronal workspace and the information integration theories of consciousness.
Frontiers in psychology
The study of non-conscious vision benefits from several alternative methods that allow the suppression of an image from awareness. Here, we present and compare two of them that are particularly well-suited for creating sustained periods of invisibility, namely visual crowding and continuous flash suppression (CFS). In visual crowding, a peripheral image surrounded by similar flankers becomes impossible to discriminate. In CFS, an image presented to one eye becomes impossible to detect when rapidly changing patterns are presented to the other eye. After discussing the experimental specificities of each method, we give a comparative overview of the main empirical results derived from them, from the mere analysis of low-level features to the extraction of semantic contents. We conclude by proposing practical guidelines and future directions to obtain more quantitative and systematic measures of non-conscious processes under prolonged stimulation.
Frontiers in psychology
Different combinations of forward and backward masking as well as interocular suppression have been used extensively to render stimuli invisible and to study those aspects of visual stimuli that are processed in the absence of conscious experience. Although the two techniques-masking vs. interocular suppression-obviously differ both in their applications and mechanisms, only little effort has been made to compare them systematically. Yet, such a comparison is crucial: existing discrepancies in the extent of unconscious processing inferred from these two techniques must be reconciled, as our understanding of unconscious vision should be independent of the technique used to prevent visibility. Here, we studied similarities and differences between faces rendered invisible by masking vs. interocular suppression using a priming paradigm. By carefully equating stimulus strength across the two techniques, we analyzed the effects of face primes with the same viewpoint (repetition priming, Experiment 1) and of face primes with a different viewpoint (identity priming, Experiment 2) on the reaction times for a fame categorization task. Overall, we found that the magnitude of both repetition and identity priming largely depended on stimulus visibility. Moreover, when the primes were subjectively invisible, both repetition and identity priming were found to be qualitatively stronger under masking than under interocular suppression. Taken together, these results help refine our understanding of which level of visual processing each technique disrupts, and illustrate the importance of systematic methodological comparisons in the field of unconscious vision.
2012
Neuropsychologia
Facial expressions are known to impact observers' behavior, even when they are not consciously identifiable. Relying on visual crowding, a perceptual phenomenon whereby peripheral faces become undiscriminable, we show that participants exposed to happy vs. neutral crowded faces rated the pleasantness of subsequent neutral targets accordingly to the facial expression's valence. Using functional magnetic resonance imaging (fMRI) along with psychophysiological interaction analysis, we investigated the neural determinants of this nonconscious preference bias, either induced by static (i.e., pictures) or dynamic (i.e., videos) facial expressions. We found that while static expressions activated primarily the ventral visual pathway (including task-related functional connectivity between the fusiform face area and the amygdala), dynamic expressions triggered the dorsal visual pathway (i.e., posterior partietal cortex) and the substantia innominata, a structure that is contiguous with the dorsal amygdala. As temporal cues are known to improve the processing of visible facial expressions, the absence of ventral activation we observed with crowded videos questions the capacity to integrate facial features and facial motions without awareness. Nevertheless, both static and dynamic facial expressions activated the hippocampus and the orbitofrontal cortex, suggesting that nonconscious preference judgments may arise from the evaluation of emotional context and the computation of aesthetic evaluation.
Frontiers in psychology
In the study of nonconscious processing, different methods have been used in order to render stimuli invisible. While their properties are well described, the level at which they disrupt nonconscious processing remains unclear. Yet, such accurate estimation of the depth of nonconscious processes is crucial for a clear differentiation between conscious and nonconscious cognition. Here, we compared the processing of facial expressions rendered invisible through gaze-contingent crowding (GCC), masking, and continuous flash suppression (CFS), three techniques relying on different properties of the visual system. We found that both pictures and videos of happy faces suppressed from awareness by GCC were processed such as to bias subsequent preference judgments. The same stimuli manipulated with visual masking and CFS did not bias significantly preference judgments, although they were processed such as to elicit perceptual priming. A significant difference in preference bias was found between GCC and CFS, but not between GCC and masking. These results provide new insights regarding the nonconscious impact of emotional features, and highlight the need for rigorous comparisons between the different methods employed to prevent perceptual awareness.
2011
Journal of vision
Sensory adaptation reflects the fact that the responsiveness of a perceptual system changes after the processing of a specific stimulus. Two manifestations of this property have been used in order to infer the mechanisms underlying vision: priming, in which the processing of a target is facilitated by prior exposure to a related adaptor, and habituation, in which this processing is hurt by overexposure to an adaptor. In the present study, we investigated the link between priming and habituation by measuring how sensory evidence (short vs. long adaptor exposure) and perceptual awareness (discriminable vs. undiscriminable adaptor stimulus) affects the adaptive response on a related target. Relying on gaze-contingent crowding, we manipulated independently adaptor discriminability and adaptor duration and inferred sensory adaptation from reaction times on the discrimination of a subsequent oriented target. When adaptor orientation was undiscriminable, we found that increasing its duration reversed priming into habituation. When adaptor orientation was discriminable, priming effects were larger after short exposure, but increasing adaptor duration led to a decrease of priming instead of a reverse into habituation. We discuss our results as reflecting changes in the temporal dynamics of angular orientation processing, depending on the mechanisms associated with perceptual awareness and attentional amplification.
Journal of vision
The conscious representation we build from the visual environment appears jumbled in the periphery, reflecting a phenomenon known as crowding. Yet, it remains possible that object-level representations (i.e., resulting from the binding of the stimulus' different features) are preserved even if they are not consciously accessible. With a paradigm involving gaze-contingent substitution, which allows us to ensure the constant absence of peripheral stimulus discrimination, we show that, despite their jumbled appearance, multi-feature crowded objects, such as faces and directional symbols, are encoded in a nonconscious manner and can influence subsequent behavior. Furthermore, we show that the encoding of complex crowded contents is modulated by attention in the absence of consciousness. These results, in addition to bringing new insights concerning the fate of crowded information, illustrate the potential of the Gaze-Contingent Crowding (GCC) approach for probing nonconscious cognition.
Psychological science
Crowding occurs when nearby flankers impede the identification of a peripheral stimulus. Here, we studied whether crowded features containing inaccessible emotional information can nevertheless affect preference judgments. We relied on gaze-contingent crowding, a novel method allowing for constant perceptual unawareness through eye-tracking control, and we found that crowded facial expressions can bias evaluative judgments of neutral pictographs. Furthermore, this emotional bias was effective not only for static images of faces, but also for videos displaying dynamic facial expressions. In addition to showing an alternative approach for probing nonconscious cognition, this study reveals that crowded information, instead of being fully suppressed, can have important influences on decisions.
2010
Stem cells and development
Cancer cells are unequal in a tumor mass and in established cultures. This is attributable to cancer stem cells with the unique ability to self-renew and to generate differentiating progeny. This ability is controlled at the level of asymmetric division by mechanisms that are yet not well defined. We found that normal and cancer keratinocyte fate was linked to the asymmetric distribution of epidermal growth factor receptor (EGFR) during mitosis. Although essential for epithelial cell proliferation, differentiation, and survival, this receptor was not present on the surface of cells satisfying criteria for stem cells such as quiescence, competence to produce functionally distinct daughters, high proliferative and clonogenic potential, sphere formation ability, and expression of stem cell markers. In contrast, keratinocytes displaying EGFR acquired a more differentiated phenotype, suggesting that EGFR may be involved in a switch from stem to transient amplifying cell fate. This switch was associated with changes in the expression profile of cell cycle, survival, and mitochondria controlling proteins that varied between normal and cancer cells. In conclusion, it appears that an unequal distribution of EGFR at mitosis controls keratinocyte fate by balancing quiescence and cycling of EGFR(-) cells, clearly malfunctioning in cancer. We believe that our findings provide mechanistic insights into the development of resistance to anti-EGFR therapies.