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New information can be learned during sleep but the extent to which we can access this knowledge after awakening is far less understood. Using a novel Associative Transfer Learning paradigm, we show that, after hearing unknown Japanese words with sounds referring to their meaning during sleep, participants could identify the images depicting the meaning of newly acquired Japanese words after awakening (N = 22). Moreover, we demonstrate that this cross-modal generalization is implicit, meaning that participants remain unaware of this knowledge. Using electroencephalography, we further show that frontal slow-wave responses to auditory stimuli during sleep predicted memory performance after awakening. This neural signature of memory formation gradually emerged over the course of the sleep phase, highlighting the dynamics of associative learning during sleep. This study provides novel evidence that the formation of new associative memories can be traced back to the dynamics of slow-wave responses to stimuli during sleep and that their implicit transfer into wakefulness can be generalized across sensory modalities.

Electrophysiological studies

Online speech processing imposes significant computational demands on the listening brain. Predictive coding provides an elegant account of the way this challenge is met through the exploitation of prior knowledge. While such accounts have accrued considerable evidence at the sublexical- and word-levels, relatively little is known about the predictive mechanisms that support sentence-level processing. Here, we exploit the 9pop-out9 phenomenon (i.e. dramatic improvement in the intelligibility of degraded speech following prior information) to investigate the psychophysiological correlates of sentence comprehension. We recorded electroencephalography and pupillometry from 21 humans (10 females) while they rated the clarity of full sentences that had been degraded via noise-vocoding or sine-wave synthesis. Sentence pop-out was reliably elicited following visual presentation of the corresponding written sentence, despite never hearing the undistorted speech. No such effect was observed following incongruent or no written information. Pop-out was associated with improved reconstruction of the acoustic stimulus envelope from low-frequency EEG activity, implying that pop-out is mediated via top-down signals that enhance the precision of cortical speech representations. Spectral analysis revealed that pop-out was accompanied by a reduction in theta-band power, consistent with predictive coding accounts of acoustic filling-in and incremental sentence processing. Moreover, delta- and alpha-band power, as well as pupil diameter, were increased following the provision of any written information. We interpret these findings as evidence of a transition to a state of active listening, whereby participants selectively engage attentional and working memory processes to evaluate the congruence between expected and actual sensory input.

People can introspect on their internal state and report the reasons driving their decisions but choice blindness (CB) experiments suggest that this ability can sometimes be a retrospective illusion. Indeed, when presented with deceptive cues, people justify choices they did not make in the first place, suggesting that external cues largely contribute to introspective processes. Yet, it remains unclear what are the respective contributions of external cues and internal decision variables in forming introspective report. Here, using a brain–computer interface, we show that internal variables continue to be monitored but are less impactful than deceptive external cues during CB episodes. Moreover, we show that deceptive cues overturn the classical relationship between confidence and accuracy: introspective failures are associated with higher confidence than genuine introspective reports. We tracked back the origin of these overconfident confabulations by revealing their prominence when internal decision evidence is weak and variable. Thus, introspection is neither a direct reading of internal variables nor a mere retrospective illusion, but rather reflects the integration of internal decision evidence and external cues, with CB being a special instance where internal evidence is inconsistent.

The controversial question of whether machines may ever be conscious must be based on a careful consideration of how consciousness arises in the only physical system that undoubtedly possesses it: the human brain. We suggest that the word “consciousness” conflates two different types of information-processing computations in the brain: the selection of information for global broadcasting, thus making it flexibly available for computation and report (C1, consciousness in the first sense), and the self-monitoring of those computations, leading to a subjective sense of certainty or error (C2, consciousness in the second sense). We argue that despite their recent successes, current machines are still mostly implementing computations that reflect unconscious processing (C0) in the human brain. We review the psychological and neural science of unconscious (C0) and conscious computations (C1 and C2) and outline how they may inspire novel machine architectures.

Sleep leads to a disconnection from the external world. Even when sleepers regain consciousness during Rapid Eye Movement (REM) sleep, little, if any, external information is incorporated into dream content. While gating mechanisms might be at play to avoid interference on dreaming activity, a total disconnection would prevent the sleeper from promptly responding to informative events (e.g., threat signals). In fact, a whole range of neural responses to external events are preserved, at least partially, during REM sleep. Thus, it remains unsettled whether external inputs are either integrated or conversely gated during REM sleep. Here, we sought to disentangle this issue by studying the impact of eye movements (EMs) on the processing of informative signals. EMs constitute a reliable predictor of reporting a dream upon awakening and induce a higher arousal threshold to external stimuli. We hypothesized that although sleepers might continue responding to external events, periods of EMs would be associated with the gating of informative signals in order to reduce interference with dreaming activity. By reconstructing perceived speech in a multi-talker, cocktail-party environment from electrophysiological responses, we show that informative speech is selectively amplified over meaningless speech during REM sleep. However, we show that at the precise timing of EMs, informative speech is, on the contrary, selectively suppressed. Importantly, this suppression did not affect the processing of non-informative signals, revealing a selective mechanism of gating for informative contents rather than a general decline in sensory encoding. These results reveal flexible mechanisms of amplification/suppression of external inputs during REM sleep, and demonstrate the impact of EMs on the selective gating of informative stimuli.

Metacognition is the ability to monitor and control cognition. Because young children often provide inaccurate metacognitive judgments when prompted to do so verbally, it has long been assumed that this ability does not develop until late childhood. This claim is now challenged by new studies using nonverbal paradigms and revealing that basic forms of metacognition—such as the ability to estimate decision confidence or to monitor errors—are present even in preverbal infants. This new line of evidence suggests that young children adapt to their environment not only by considering their physical and social surroundings but also by reflecting on their own cognitive states.

Scientific research on consciousness is critical to multiple scientific, clinical, and ethical issues. The growth of the field could also be beneficial to several areas including neurology and mental health research. To achieve this goal, we need to set funding priorities carefully and address problems such as job creation and potential media misrepresentation., SCOPUS: no.j, info:eu-repo/semantics/published

Introduction It has long been posited that threat learning operates and forms under an affective and a cognitive learning system that is supported by different brain circuits. A primary drawback in exposure‐based therapies is the high rate of relapse that occurs when higher order areas fail to inhibit responses driven by the defensive circuit. It has been shown that implicit exposure of fearful stimuli leads to a long‐lasting reduction in avoidance behavior in patients with phobia. Despite the potential benefits of this approach in the treatment of phobias and posttraumatic stress disorder, implicit extinction is still underinvestigated. Methods Two groups of healthy participants were threat conditioned. The following day, extinction training was conducted using a stereoscope. One group of participants was explicitly exposed with the threat‐conditioned image, while the other group was implicitly exposed using a continuous flash suppression (CFS) technique. On the third day, we tested the spontaneous recovery of defensive responses using explicit presentations of the images. Results On the third day, we found that only the implicit extinction group showed reduced spontaneous recovery of defensive responses to the threat‐conditioned stimulus, measured by threat‐potentiated startle responses but not by the electrodermal activity. Conclusion Our results suggest that implicit extinction using CFS might facilitate the modulation of the affective component of fearful memories, attenuating its expression after 24 hr. The limitations of the CFS technique using threatful stimuli urge the development of new strategies to improve implicit presentations and circumvent such limitations. Our study encourages further investigations of implicit extinction as a potential therapeutic target to further advance exposure‐based psychotherapies.

It has long been posited that threat learning operates and forms under an affective and a cognitive learning system that are supported by different brain circuits. A primary drawback in exposure-based therapies is the high rate of relapse when higher order inhibitory structures failed to inhibit the emotional responses driven by the defensive circuit. It has been shown that implicit exposure of fearful stimuli leads to a long-lasting reduction of avoidance behavior in patients with phobia through the facilitation of fear processing areas in the absence of subjective fear. Despite the potential benefits of this approach in the treatment of phobias and PTSD, implicit exposure to fearful stimuli is still under-investigated. Here, we used unconscious presentation of threat-conditioned stimuli in healthy humans, using a continuous flash suppression technique. We found that implicit exposure of a conditioned stimulus reduced, on the following day, defensive responses to the conditioned stimulus measured by threat-potentiated startle responses but not by the electrodermal activity. Our results suggest that implicit exposure using CFS might facilitate the modulation of the affective component of fearful memories, representing an important therapeutic target to further advance exposure-based psychotherapies.

Stimulus repetition induces attenuated brain responses. This phenomenon, termed repetition suppression (RS), is classically held to stem from bottom-up neuronal adaptation. However, recent studies suggest that RS is driven by top-down predictive mechanisms. It remains controversial whether these top-down mechanisms of RS rely on conscious strategies, or if they represent a more fundamental aspect of perception, coding for physical properties of the repeated feature. The presence of top-down effects in the absence of perceptual awareness would indicate that conscious strategies are not sufficient to explain top-down mechanisms of RS. We combined an unconscious priming paradigm with EEG recordings and tested whether RS can be modulated by the probability of encountering a repetition, even in the absence of awareness. Our results show that both behavioural priming and RS near occipital areas are modulated by repetition probability, regardless of prime awareness. This contradicts previous findings that have argued that RS modulation is a by-product of conscious strategies. In contrast, we found that the increase in theta-band power following unrepeated trials – an index of conflict detection – is modulated only by expectations during conscious primes, implicating the use of conscious strategies. Together, our results suggest that the influence of predictions on RS can be either automatic in sensory brain regions or dependent on conscious strategies.

Unconscious processes have been shown to affect both perception and behaviour. However, the flexibility of such processes remains unknown. Here we investigate whether unconscious decisional processes can adapt to the utility of sensory information. To this end, we had participants gradually accumulate information from noisy motion stimuli, until a decision was reached. We titrated conscious awareness of these stimuli by simultaneously presenting a dynamic dichoptic mask. Crucially, we manipulated the likelihood that the suppressed portion of each presentation would contain useful information. Our results show that the statistics of the environment can be used to modulate unconscious evidence accumulation, resulting in faster choices. Furthermore, computational modelling revealed that this modulation is due to a change in the quality of unconscious evidence accumulation, rather than a conscious change in strategy. Together, these results indicate that unconscious decisional mechanisms are capable of optimising performance by flexibly adapting to the statistical environment.

Summary Falling asleep leads to a loss of sensory awareness and to the inability to interact with the environment [1]. While this was traditionally thought as a consequence of the brain shutting down to external inputs, it is now acknowledged that incoming stimuli can still be processed, at least to some extent, during sleep [2]. For instance, sleeping participants can create novel sensory associations between tones and odors [3] or reactivate existing semantic associations, as evidenced by event-related potentials [4–7]. Yet, the extent to which the brain continues to process external stimuli remains largely unknown. In particular, it remains unclear whether sensory information can be processed in a flexible and task-dependent manner by the sleeping brain, all the way up to the preparation of relevant actions. Here, using semantic categorization and lexical decision tasks, we studied task-relevant responses triggered by spoken stimuli in the sleeping brain. Awake participants classified words as either animals or objects (experiment 1) or as either words or pseudowords (experiment 2) by pressing a button with their right or left hand, while transitioning toward sleep. The lateralized readiness potential (LRP), an electrophysiological index of response preparation, revealed that task-specific preparatory responses are preserved during sleep. These findings demonstrate that despite the absence of awareness and behavioral responsiveness, sleepers can still extract task-relevant information from external stimuli and covertly prepare for appropriate motor responses., Highlights • Subjects classifying spoken words continue performing the task after falling asleep • Movement-related brain activity in the absence of overt behavior is demonstrated • The sleeping brain can process spoken words in a task-dependent manner • Response preparation is slower in sleep than in wakefulness, Kouider et al. show that subjects doing semantic categorization of spoken words continue performing this task after falling asleep. Analyses of neural activity in sleep shows a motor preparation bias for the correct response hand in the absence of overt behavior. Thus, the sleeping brain can process external stimuli in a task-dependent manner.

Subliminal stimuli can affect perception, decision-making, and action without being accessible to conscious awareness. Most evidence supporting this notion has been obtained in highly controlled laboratory conditions. Hence, its generalization to more realistic and ecologically valid contexts is unclear. Here, we investigate the impact of subliminal cues in an immersive navigation task using the so-called eXperience Induction Machine (XIM), a human accessible mixed-reality system. Subjects were asked to navigate through a maze at high speed. At irregular intervals, one group of subjects was exposed to subliminal aversive stimuli using the masking paradigm. We hypothesized that these stimuli would bias decision-making. Indeed, our results confirm this hypothesis and indicate that a subliminal channel of interaction exists between the user and the XIM. These results are relevant in our understanding of the bandwidth of communication that can be established between humans and their physical and social environment, thus opening up to new and powerful methods to interface humans and artefacts.

Sleep is characterized by a loss of behavioral responsiveness. However, recent research has shown that the sleeping brain is not completely disconnected from its environment. How neural activity constrains the ability to process sensory information while asleep is yet unclear. Here, we instructed human volunteers to classify words with lateralized hand responses while falling asleep. Using an electroencephalographic (EEG) marker of motor preparation, we show how responsiveness is modulated across sleep. These modulations are tracked using classic event-related potential analyses complemented by Lempel-Ziv complexity (LZc), a measure shown to track arousal in sleep and anesthesia. Neural activity related to the semantic content of stimuli was conserved in light non-rapid eye movement (NREM) sleep. However, these processes were suppressed in deep NREM sleep and, importantly, also in REM sleep, despite the recovery of wake-like neural activity in the latter. In NREM sleep, sensory activations were counterbalanced by evoked down states, which, when present, blocked further processing of external information. In addition, responsiveness markers correlated positively with baseline complexity, which could be related to modulation in sleep depth. In REM sleep, however, this relationship was reversed. We therefore propose that, in REM sleep, endogenously generated processes compete with the processing of external input. Sleep can thus be seen as a self-regulated process in which external information can be processed in lighter stages but suppressed in deeper stages. Last, our results suggest drastically different gating mechanisms in NREM and REM sleep. SIGNIFICANCE STATEMENT Previous research has tempered the notion that sleepers are isolated from their environment. Here, we pushed this idea forward and examined, across all sleep stages, the brain9s ability to flexibly process sensory information, up to the decision level. We extracted an EEG marker of motor preparation to determine the completion of the sensory processing chain and explored how it is constrained by baseline and evoked neural activity. In NREM sleep, slow waves elicited by stimuli appeared to block response preparation. We also used a novel analytic approach (Lempel-Ziv complexity) and showed that the ability to process external information correlates with neural complexity. A reversal of the correlation between complexity and motor indices in REM sleep suggests drastically different gating mechanisms across sleep stages.

Previous research has shown that stimuli rendered invisible through masking can be sufficiently processed to induce nonconscious influences and facilitate subsequent recognition. However, masking paradigms are methodologically restricted such that stimuli cannot be presented for longer than a few tens of milliseconds, potentially restricting the strength of nonconscious influences. By adapting a masked face repetition priming paradigm to a recent interocular suppression method, we investigated whether longer periods of invisible prime stimulation lead to larger nonconscious influences on subsequent recognition. Surprisingly, we found that while brief periods of invisible prime stimulation result in classical facilitation priming, long periods of invisible stimulation lead to negative priming influences, reflecting impairment of subsequent recognition. In contrast, when the prime was visible, longer exposure resulted in classical facilitation effects, revealing qualitative differences between conscious and nonconscious processes. Altogether, the present findings reveal the existence of a nonconscious overstimulation cost, as well as an important dissociation between conscious and nonconscious processing.

Affective priming (AP) is a well-established phenomenon in which performance to a valenced target is typically better when it is preceded by an affectively congruent prime than when it is preceded by an incongruent prime. Several studies have emphasized a strong similarity between AP and Stroop suggesting that both are driven by response interference. The present study investigated this hypothesis by testing whether a general prediction of the response interference model was verified in the two tasks. This prediction refers to target strength and states that the size of compatibility effects should increase as the strength of the relevant information decreases. In four experiments, we show that this general prediction of the response interference model was verified in AP and Stroop when the strength of the relevant information was manipulated at the perceptual level (Experiments 1 and 2), while the opposite pattern was observed when this variable was manipulated at the semantic level (Experiments 3 and 4). While the results do not undermine the hypothesis that AP and Stroop effects are governed by response interference, they suggest that the model should be refined in order to account for differential effects of target strength in compatibility tasks.

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.

Most bilinguals understand their second language more slowly than their first. This behavioral asymmetry may arise from the perceptual, phonological, lexicosemantic, or strategic components of bilingual word processing. However, little is known about the neural source of such language dominance and how it is regulated in the bilingual brain. Using functional magnetic resonance imaging, we found that unconscious neural priming in bilingual word recognition is language nonselective in the left midfusiform gyrus but exhibits a preference for the dominant language in the left posterior middle temporal gyrus (MTG). These early-stage components of reading were located slightly upstream of the left midlateral MTG, which exhibited enhanced response during a conscious switch of language. Effective connectivity analysis revealed that this language switch is triggered by reentrant signals from inferior frontal cortex and not by bottom-up signals from occipitotemporal cortex. We further confirmed that magnetic stimulation of the same inferior frontal region interferes with conscious language control but does not disrupt unconscious priming by masked words. Collectively, our results demonstrate that the neural bottleneck in the bilingual brain is a cross-language asymmetry of form-meaning association in inferolateral temporal cortex, which is overcome by a top-down cognitive control for implementing a task schema in each language.

International audience; We often feel that our perceptual experience is richer than what we can express. For instance, when flashed with a large set of letters, we feel that we can see them all, while we can report only a few. However, the nature of this subjective impression remains highly debated: while many favour a dissociation between two forms of consciousness (access vs. phenomenal consciousness), others contend that the richness of phenomenal experience is a mere illusion. Here we addressed this question with a classical partial-report paradigm now modified to include unexpected items in the unreported parts of the stimuli. We show that even in the presence of unexpected pseudo-letters, participants still felt that there were only letters. Additionally, we show that this feeling reflects an illusion whereby participants reconstruct letters using partial letter-like information. We propose that the feeling of seeing emerges from the interplay between partially accessible information and expectations.

Whether masked number priming involves a low-level sensorimotor route or an amodal semantic level of processing remains highly debated. Several alternative interpretations have been put forward, proposing either that masked number priming is solely a byproduct of practice with numbers, or that stimulus awareness was underestimated. In a series of four experiments, we studied whether repetition and congruity priming for numbers reliably extend to novel (i.e., unpracticed) stimuli and whether priming transfers from a visual prime to an auditory target, even when carefully controlling for stimulus awareness. While we consistently observed cross-modal priming, the generalization to novel stimuli was weaker and reached significance only when considering the whole set of experiments. We conclude that number priming does involve an amodal, semantic level of processing, but is also modulated by task settings.

Long-term priming studies of lexical processing have yielded conflicting claims as to whether abstract versus episodic representations are involved during word recognition. A critical piece of evidence that could separate the two accounts rests on the existence of full morphological priming, where morphologically related words yield the same amount of priming as repeated words. In this study, participants performed speeded lexical decision on lists of auditory words and non-words, which contained repeated, morphologically related, semantically related and phonologically related pairs of items. In order to minimize the involvement of episodic factors, we increased the prime–target interval and decreased their physical similarity by introducing a change in speaker’s voice. We show that under conditions that minimize access to episodic features, the magnitude of repetition priming decreased to attain that of morphological priming. Importantly, morphological and repetition priming for words were always observed in the absence of any semantic and phonological priming, suggesting that they cannot be reduced to formal or meaning overlap. Our results support the view that long-term priming taps both abstract lexical codes with a morphological format and episodic memory components. Further, they show that episodic influences on priming can be modulated by prime–target interval and physical similarity.

International audience; Current theories of consciousness assume a qualitative dissociation between conscious and unconscious processing: while subliminal stimuli only elicit a transient activity, supraliminal stimuli have long-lasting influences. Nevertheless, the existence of this qualitative distinction remains controversial, as past studies confounded awareness and stimulus strength (energy, duration). Here, we used a masked speech priming method in conjunction with a submillisecond interaural delay manipulation to contrast subliminal and supraliminal processing at constant prime, mask and target strength. This delay induced a perceptual streaming effect, with the prime popping out in the supraliminal condition. By manipulating the prime-target interval (ISI), we show a qualitatively distinct profile of priming longevity as a function of prime awareness. While subliminal priming disappeared after half a second, supraliminal priming was independent of ISI. This shows that the distinction between conscious and unconscious processing depends on high-level perceptual streaming factors rather than low-level features (energy, duration).

It is often assumed that neural activity in face-responsive regions of primate cortex correlates with conscious perception of faces. However, whether such activity occurs without awareness is still debated. Using functional magnetic resonance imaging (fMRI) in conjunction with a novel masked face priming paradigm, we observed neural modulations that could not be attributed to perceptual awareness. More specifically, we found reduced activity in several classic face-processing regions, including the “fusiform face area,” “occipital face area,” and superior temporal sulcus, when a face was preceded by a briefly flashed image of the same face, relative to a different face, even when 2 images of the same face differed. Importantly, unlike most previous studies, which have minimized awareness by using conditions of inattention, the present results occurred when the stimuli (the primes) were attended. By contrast, when primes were perceived consciously, in a long-lag priming paradigm, we found repetition-related activity increases in additional frontal and parietal regions. These data not only demonstrate that fMRI activity in face-responsive regions can be modulated independently of perceptual awareness, but also document where such subliminal face-processing occurs (i.e., restricted to face-responsive regions of occipital and temporal cortex) and to what extent (i.e., independent of the specific image).

Using a sandwich-masked priming paradigm with faces, we report two ERP effects that appear to reflect different levels of subliminal face processing. These two ERP repetition effects dissociate in their onset, scalp topography, and sensitivity to face familiarity. The “early” effect occurred between 100 and 150 ms, was maximally negative-going over lateral temporoparietal channels, and was found for both familiar and unfamiliar faces. The “late” effect occurred between 300 and 500 ms, was maximally positive-going over centroparietal channels, and was found only for familiar faces. The early effect resembled our previous fMRI data from the same paradigm; the late effect resembled the behavioural priming found, in the form of faster reaction times to make fame judgments about primed relative to unprimed familiar faces. None of the ERP or behavioural effects appeared explicable by a measure of participants’ ability to see the primes. The ERP and behavioural effects showed some sensitivity to whether the same or a different photograph of a face was repeated, but could remain reliable across different photographs, and did not appear attributable to a low-level measure of pixelwise overlap between prime and probe photograph. The functional significance of these ERP effects is discussed in relation to unconscious perception and face processing.

Prior expectations shape neural responses in sensory regions of the brain, consistent with a Bayesian predictive coding account of perception. Yet, it remains unclear whether such a mechanism is already functional during early stages of development. To address this issue, we study how the infant brain responds to prediction violations using a cross-modal cueing paradigm. We record electroencephalographic responses to expected and unexpected visual events preceded by auditory cues in 12-month-old infants. We find an increased response for unexpected events. However, this effect of prediction error is only observed during late processing stages associated with conscious access mechanisms. In contrast, early perceptual components reveal an amplification of neural responses for predicted relative to surprising events, suggesting that selective attention enhances perceptual processing for expected events. Taken together, these results demonstrate that cross-modal statistical regularities are used to generate predictions that differentially influence early and late neural responses in infants., Prior expectations shape neural processing in the brain and violations of these expectations can have a profound influence on learning. Here the authors demonstrate that such predictive coding mechanisms are already functional in the brains of 12-month-old infants.

According to theoretical frameworks casting perception as inference, vision results from the integration of bottom-up visual input with top-down expectations. Under conditions of strongly degraded sensory input, this may occasionally result in false perceptions in the absence of a sensory signal, also termed “hallucinations.” Here, we investigated whether spontaneous prestimulus activity patterns in sensory circuits, which may embody a participant's prior expectations, predispose the observer toward false perceptions. Specifically, we used fMRI to investigate whether the representational content of prestimulus activity in early visual cortex is linked to subsequent perception during a challenging detection task. Human participants were asked to detect oriented gratings of a particular orientation that were embedded in noise. We found two characteristics of prestimulus activity that predisposed participants to hallucinations: overall lower prestimulus activity and a bias in the prestimulus activity patterns toward the to-be-detected (expected) grating. These results suggest that perceptual hallucinations may be due to an imprecise and biased state of sensory circuits preceding sensory evidence collection.SIGNIFICANCE STATEMENTWhen sensory stimulation is strongly degraded, we occasionally misperceive a stimulus when only noise is present: a perceptual hallucination. Using fMRI in healthy participants, we investigated whether the state of early visual cortex preceding stimulus onset predisposes an observer to hallucinations. We found two characteristics of prestimulus activity that predisposed participants to hallucinations: overall lower prestimulus activity and a bias in the prestimulus activity patterns toward the expected grating. These results suggest that perceptual hallucinations are due to an imprecise and biased state of sensory circuits preceding sensation.

SummaryExperience continuously imprints on the brain at all stages of life. The traces it leaves behind can produce perceptual learning [1], which drives adaptive behavior to previously encountered stimuli. Recently, it has been shown that even random noise, a type of sound devoid of acoustic structure, can trigger fast and robust perceptual learning after repeated exposure [2]. Here, by combining psychophysics, electroencephalography (EEG), and modeling, we show that the perceptual learning of noise is associated with evoked potentials, without any salient physical discontinuity or obvious acoustic landmark in the sound. Rather, the potentials appeared whenever a memory trace was observed behaviorally. Such memory-evoked potentials were characterized by early latencies and auditory topographies, consistent with a sensory origin. Furthermore, they were generated even on conditions of diverted attention. The EEG waveforms could be modeled as standard evoked responses to auditory events (N1-P2) [3], triggered by idiosyncratic perceptual features acquired through learning. Thus, we argue that the learning of noise is accompanied by the rapid formation of sharp neural selectivity to arbitrary and complex acoustic patterns, within sensory regions. Such a mechanism bridges the gap between the short-term and longer-term plasticity observed in the learning of noise [2, 4–6]. It could also be key to the processing of natural sounds within auditory cortices [7], suggesting that the neural code for sound source identification will be shaped by experience as well as by acoustics.

International audience; During speech perception, listeners compensate for phonological rules of their language. For instance, English place assimilation causes green boat to be typically pronounced as greem boat; English listeners, however, perceptually compensate for this rule and retrieve the intended sound (n). Previous research using EEG has focused on rules with clear phonetic underpinnings, showing that perceptual compensation occurs at an early stage of speech perception. We tested whether this early mechanism also accounts for the compensation for more complex rules. We examined compensation for French voicing assimilation , a rule with abstract phonological restrictions on the contexts in which it applies. Our results reveal that perceptual compensation for this rule by French listeners modulates an early ERP component. This is evidence that early stages of speech sound categorization are sensitive to complex phonological rules of the native language.

We present data from a preferential looking method to investigate when infants have mapped singular and plural markers in English onto the semantic distinction between singleton sets and sets with more than 1 individual. Twenty- to 36-month-old children heard sentences that marked number in 1 of 2 ways: (a) redundantly with verb morphology, lexical quantifiers, and noun morphology ("Look, there ARE SOME blicketS"/"Look, there IS A blicket") or (b) only with noun morphology ("Look at the blicketS"/"Look at the blicket"). Twenty-four-month-old infants, but not 20-month-old infants, looked at the screen that matched the carrier sentence with respect to singular-plural distinction when number was expressed on the verb, on the noun, and with quantifiers. Detailed looking-time analyses suggest that the arrays begin to be differentiated on the child's hearing are or is. Twenty-four-month-olds failed when number was marked on the noun alone, whereas 36-month-olds succeeded in this condition. These data suggest th...

We present a novel subliminal priming technique that operates in the auditory modality. Masking is achieved by hiding a spoken word within a stream of time-compressed speechlike sounds with similar spectral characteristics. Participants were unable to consciously identify the hidden words, yet reliable repetition priming was found. This effect was unaffected by a change in the speaker's voice and remained restricted to lexical processing. The results show that the speech modality, like the written modality, involves the automatic extraction of abstract word-form representations that do not include non-linguistic details. In both cases, priming operates at the level of discrete and abstract lexical entries and is little influenced by overlap in form or semantics.

The role of the basal ganglia, and more specifically of the striatum, in language is still debated. Recent studies have proposed that linguistic abilities involve two distinct types of processes: the retrieving of stored information, implicating temporal lobe areas, and the application of combinatorial rules, implicating fronto-striatal circuits. Studies of patients with focal lesions and neurodegenerative diseases have suggested a role for the striatum in morphological rule application, but functional imaging studies found that the left caudate was involved in syntactic processing and not morphological processing. In the present study, we tested the view that the basal ganglia are involved in rule application and not in lexical retrieving in a model of striatal dysfunction, namely Huntington's disease at early stages. We assessed the rule-lexicon dichotomy in the linguistic domain with morphology (conjugation of non-verbs and verbs) and syntax (sentence comprehension) and in a non-linguistic domain with arithmetic operations (subtraction and multiplication). Thirty Huntington's disease patients (15 at stage I and 15 at stage II) and 20 controls matched for their age and cultural level were included in this study. Huntington's disease patients were also assessed using the Unified Huntington's Disease Rating Scale (UHDRS) and MRI. We found that early Huntington's disease patients were impaired in rule application in the linguistic and non-linguistic domains (morphology, syntax and subtraction), whereas they were broadly spared with lexical processing. The pattern of performance was similar in patients at stage I and stage II, except that stage II patients were more impaired in all tasks assessing rules and had in addition a very slight impairment in the lexical condition of conjugation. Finally, syntactic rule abilities correlated with all markers of the disease evolution including bicaudate ratio and performance in executive function, whereas there was no correlation with arithmetic and morphological abilities. Together, this suggests that the striatum is involved in rule processing more than in lexical processing and that it extends to linguistic and non-linguistic domains. These results are discussed in terms of domain-specific versus domain-general processes of rule application.