Biology subjects

Cappe, C.

Publications and source records attributed to Cappe, C..

7 recordsLinked to original sources

bioRxiv2026

Cerebral bases of audiovisual temporal binding window: an awake surgery study

BackgroundAudiovisual integration is essential for daily functions such as speech comprehension. It relies on a temporal constraint whereby events from different sensory modalities are perceptually bound within a limited temporal window, the audiovisual temporal binding window, defining the range of stimulus onset asynchronies perceived as synchronous. While correlational neuroimaging studies (fMRI, EEG) have implicated a distributed network in audiovisual integration, the causal neural underpinnings of the temporal binding window remain largely unknown. ObjectiveTo identify cortical regions causally supporting audiovisual simultaneity judgment. Methods: Direct electrical stimulation (DES) was prospectively applied to 62 cortical sites during awake brain surgery in 39 patients. Patients performed an audiovisual simultaneity judgment task with varying stimuli onset asynchronies alongside standard sensory-motor, language, and visuospatial tasks. Montreal Neurological Institute coordinates were obtained for all stimulated areas. ResultsDES selectively impaired audiovisual simultaneity judgments while sparing other standard tasks, in 7 highly focal, right-hemispheric cortical sites (<1 cm2). Three sites were situated around the intraparietal sulcus, and four near the supplementary motor area. Stimulation of left-hemisphere sites produced non-selective impairments, also affecting language-related tasks. ConclusionsThese findings provide causal evidence for a right-lateralized frontoparietal network, involving focal regions near the intraparietal sulcus and supplementary motor area, in audiovisual temporal integration. Given the established roles of these regions in attentional and decisional processes, this study refines their contribution to the temporal binding window network and underscores the clinical importance of preserving this network during awake brain surgery.

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bioRxiv2025

Cerebral Bases and Neural Dynamics of Audiovisual Temporal Binding Window: a TMS study

The temporal binding window (TBW) refers to the time interval within which two stimuli, typically visual and auditory, are perceived as synchronous. Neural bases underlying this process consistently implicate a large-scale network with superior temporal sulcus (STS) as a central hub, alongside contributions from primary auditory and visual cortices and higher-order areas including prefrontal and posterior parietal cortex. This study aimed to provide causal evidence for the involvement of superior temporal gyrus (STG) and intraparietal sulcus (IPS) in the simultaneity judgment (SJ) task using MRI-guided transcranial magnetic stimulation (TMS). In particular, we aimed to clarify temporal dynamics of these regions in audiovisual synchrony perception. Forty adults performed an SJ task in which they had to determine whether stimuli were synchronous or asynchronous. Single-pulse TMS was applied over bilateral IPS, STG, or the vertex at different delays following stimulus offset. Early stimulation of left IPS and right STG increased the proportion of "synchronous" responses. In contrast, later stimulation of bilateral STG was associated with reduced synchrony perception. These findings provide causal evidence for a dynamic interplay between parietal and temporal regions in audiovisual temporal integration. Early IPS and STG involvement facilitates temporal integration, while later STG activity promotes perceptual segregation.

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bioRxiv2025

A phase-based mechanism of attentional selection in the auditory system

Perceptual targets are often easier to detect and process if they occur at a predictable time. This perceptual benefit of temporal predictability suggests that neural resources are allocated to specific moments predicted to be most informative, or away from those predicted to be distracting. The sensitivity to sensory information changes with the phase of neural oscillations. An alignment of oscillatory phase according to the predicted time and relevance of expected events has therefore been proposed as a mechanism underlying attentional selection. This hypothesis predicts that opposite phases are aligned to relevant and distracting events so that the former are amplified and the latter suppressed, but such an effect remained to be demonstrated. We presented 25 human participants with acoustic stimuli that occurred at a predictable or unpredictable time during a pitch-discrimination task. Temporal predictability did not only lead to faster reaction times, but it also aligned the phase of beta oscillations in the electroencephalogram (EEG) in anticipation of the stimulus. Crucially, the aligned phase was opposite, depending on whether the stimulus was relevant or a distractor for the task. Single-trial deviations from the mean aligned phases slowed down behavioural responses, demonstrating functional significance of the observed neural effects. All effects occurred in the absence of rhythmic stimulation, an important but rarely tested criterion to rule out spurious phase alignment from preceding events in a stimulus sequence. We therefore conclude that the alignment of oscillatory phase underlies the selection of sensory information in time. We speculate that beta oscillations allocate neural resources in networks comprising auditory and sensorimotor regions to the expected time of auditory information, facilitating behavioural responses to upcoming events.

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bioRxiv2024

Frequency coding of multisensory integration in the local field potentials of the medial pulvinar

The pulvinar is a posterior thalamic nucleus, with a heterogeneous anatomo-functional organization. It is divided into four parts, including the medial pulvinar, which is densely connected with primary unisensory and multisensory cortical regions, and subcortical structures, including the superior colliculus. Based on this connectivity, the medial pulvinar may play an important role in sensory processing and multisensory integration. However, its contribution to multisensory integration has rarely been directly investigated. To fill this knowledge gap, two macaque monkeys were trained on a fixation task, during which auditory, visual and audiovisual stimuli were presented. We characterize local field potentials of the medial pulvinar associated with these stimuli. In the temporal domain, we describe an early and a late period showing multisensory integration, both dominated by sub-additive processes (the audiovisual response is inferior to the sum of the unisensory responses). In the frequency domain, multisensory integration, mostly sub-additive, is predominant in the lower frequencies (90% of recorded signals in 4.5-8.5Hz and 96% in 8.5-20Hz). Prevalence largely decreases in high frequencies (54% in 35-60Hz, 37% in 60-120Hz). This suggests that the medial pulvinar is a multisensory hub, integrating visual and auditory information in different frequency bands and contributing to cortico-pulvino-cortical multisensory computational loops.

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bioRxiv2023

Oscillatory traveling waves reveal predictive coding abnormalities in schizophrenia

The computational mechanisms underlying psychiatric disorders are hotly debated. One hypothesis, grounded in the Bayesian predictive coding framework, proposes that schizophrenia patients have abnormalities in encoding prior beliefs about the environment, resulting in abnormal sensory inference, which can explain core aspects of the psychopathology, such as some of its symptoms. Here, we tested this hypothesis by identifying oscillatory traveling waves as neural signatures of predictive coding. By analyzing a EEG dataset. comprising 146 schizophrenia patients and 96 age-matched healthy controls, we found that schizophrenia patients have stronger top-down alpha-band traveling waves compared to healthy controls during resting state, reflecting stronger precise priors at higher levels of the predictive processing hierarchy. Conversely, we found stronger bottom-up alpha-band waves in schizophrenia patients during a visual task reflecting an alteration of lower sensory priors. Our results yield a novel spatial-based characterization of oscillatory dynamics in schizophrenia, considering brain rhythms as traveling waves and providing a unique framework to study the different components involved in a predictive coding scheme. Altogether, our findings significantly advance our understanding of the mechanisms involved in fundamental pathophysiological aspects of schizophrenia, promoting a more comprehensive and hypothesis-driven approach to psychiatric disorders. SignificanceWe provide novel evidence favoring the Bayesian predictive coding interpretation of schizophrenia. Relying on computational and experimental works that characterized electrophysiological correlates of predictive processes, we investigate oscillatory traveling waves in EEG data of 146 schizophrenia patients and 96 age-matched healthy controls. Our results reveal stronger top-down alpha-band traveling waves in schizophrenia patients, reflecting an increase in the precision of high-level priors. On the other hand, we observed an increase in bottom-up alpha-band waves during a visual task, in line with the proposed reduction in precision of low-level sensory priors. Our findings suggest that traveling waves analysis is a versatile technique to probe predictive processing mechanisms in different cognitive processes. Impairments in this mechanism may underlie perceptual alterations as well as the pronounced clinical symptoms of schizophrenia. The strong hypothesis-driven nature of our results accentuates the relevance of our findings.

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bioRxiv2022

Multisensory integration in neurons of the medial pulvinar of macaque monkey

The pulvinar is a heterogeneous thalamic nucleus, which is well developed in primates. One of its subdivisions, the medial pulvinar, is connected to many cortical areas, including the visual, auditory and somatosensory cortices, as well as with multisensory areas and premotor areas. However, except for the visual modality, little is known about its sensory functions. A hypothesis is that, as a region of convergence of information from different sensory modalities, the medial pulvinar plays a role in multisensory integration. To test this hypothesis, two macaque monkeys were trained to a fixation task and the responses of single-units to visual, auditory and auditory-visual stimuli were examined. Analysis revealed auditory, visual and multisensory neurons in the medial pulvinar. It also revealed multisensory integration in this structure, mainly subadditive and suppressive. These findings show that the medial pulvinar is involved in multisensory integration.

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bioRxiv2019

The interplay between multisensory integration and perceptual decision making

Facing perceptual uncertainty, the brain combines information from different senses to shape optimal decision making and to guide behavior. Despite overlapping neural networks underlying multisensory integration and perceptual decision making, the process chain of decision formation has been studied mostly in unimodal contexts and is thought to be supramodal. To reveal whether and how multisensory processing interplay with perceptual decision making, we devised a paradigm mimicking naturalistic situations where human participants were exposed to continuous cacophonous audiovisual inputs containing an unpredictable relevant signal cue in one or two modalities. Using multivariate pattern analysis on concurrently recorded EEG, we decoded the neural signatures of sensory encoding and decision formation stages. Generalization analyses across conditions and time revealed that multisensory signal cues were processed faster during both processing stages. We further established that acceleration of neural dynamics was directly linked to two distinct multisensory integration processes and associated with multisensory benefit. Our results, substantiated in both detection and categorization tasks, provide evidence that the brain integrates signals from different modalities at both the sensory encoding and the decision formation stages.

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