Biology subjects

Colnat-Coulbois, S.

Publications and source records attributed to Colnat-Coulbois, S..

5 recordsLinked to original sources

bioRxiv2026

Intracerebral recordings in humans reveal gradual emergence of musical beat representation across the dorsal auditory pathway

When experiencing music, humans readily perceive and move along with a periodic beat. This ability has been proposed to rely on an enhanced representation of the beat periodicity in brain activity. However, whether this beat representation is achieved in sensory areas or whether it involves associative brain regions remains debated. Here, we addressed this question using intracerebral depth electrodes implanted in 13 human individuals to record local field potentials directly inside the brain. Participants were presented with an acoustic rhythm known to induce perception of a consistent beat across Western adults. The rhythmic stimulus elicited significant responses in a number of areas, especially superior temporal, parietal and frontal cortices located along the dorsal auditory pathway. Notably, these regions, including the primary auditory cortex but also frontal motor regions, showed significantly enhanced beat periodicity as compared to a biomimetic model of subcortical auditory processing. This beat representation was further sharpened in the inferior parietal lobe, indicating that this associative region may play a key role in the mapping between rhythmic inputs and perceptual templates of beat, in line with its posited function as a sensory-motor interface. Together, these findings provide direct evidence for a gradual transformation of rhythmic sensory input into an abstract representation of beat periodicity. This process appears to rely on the dorsal auditory pathway as a functional network supporting the categorization of rhythmic stimuli into behaviorally relevant timing templates that may be experienced as the beat.

neuroscience↗

bioRxiv2025

Concurrent category-selective neural activity across the ventral occipito-temporal cortex supports a non-hierarchical view of human visual recognition

Visual recognition is a fundamental human brain function, supported by a network of regions in the ventral occipito-temporal cortex (VOTC). This network is thought to be organized hierarchically, with definite processing stages increasing in invariance and time-course from posterior to anterior cortical regions. Here we provide a stringent test of this view by measuring category-selective neural activity to natural images of faces across the VOTC with electrophysiological intracerebral recordings in a large human sample (N=140; >11000 recording sites). Face-selective high frequency broadband (30-160 Hz) neural activity is distributed across the VOTC, with right-hemispheric dominance and regional peaks of activity. Crucially, while a progressive increase in degree of category-selectivity is found along the postero-anterior axis, neural activity occurs largely concurrently ([~]100ms onset - [~]450ms offset) across all VOTC regions. These observations challenge the standard hierarchical view of neural organization of visual object recognition in the human association cortex, supporting alternative models of this key brain function.

neuroscience↗

bioRxiv2022

Low and high frequency intracranial neural signals match in the human associative cortex

In vivo intracranial recordings of neural activity offer a unique opportunity to understand human brain function. Intracranial electrophysiological (iEEG) activity related to sensory, cognitive or motor events manifests mostly in two types of signals: event-related local field potentials in lower frequency bands (<30 Hz, LF) and broadband activity in the higher end of the frequency spectrum (>30 Hz, High frequency, HF). While most current studies rely exclusively on HF, thought to be more focal and closely related to spiking activity, the relationship between HF and LF signals is unclear, especially in human associative cortex. Here we provide a large-scale in-depth investigation of the spatial and functional relationship between these 2 signals based on intracranial recordings from 121 individual brains (8000 recording sites). We measure selective responses to complex ecologically salient visual stimuli - human faces - across a wide cortical territory in the ventral occipito-temporal cortex (VOTC), with a frequency-tagging method providing high signal-to-noise ratio (SNR) and the same objective quantification of signal and noise for the two frequency ranges. While LF face-selective activity has higher SNR across the VOTC, leading to a larger number of significant electrode contacts especially in the anterior temporal lobe, LF and HF display highly similar spatial, functional, and timing properties. Specifically, and contrary to a widespread assumption, our results point to nearly identical spatial distribution and local spatial extent of LF and HF activity at equal SNR. These observations go a long way towards clarifying the relationship between the two main iEEG signals and reestablish the informative value of LF iEEG to understand human brain function.

neuroscience↗

bioRxiv2020

Dissociated face- and word-selective intracerebral responses in the human ventral occipito-temporal cortex

The extent to which faces and written words share neural circuitry in the human brain is actively debated. Here we compared face-selective and word-selective responses in a large group of patients (N = 37) implanted with intracerebral depth electrodes in the ventral occipito-temporal cortex (VOTC). Both face-selective (i.e., significantly different responses to faces vs. nonface visual objects) and word-selective (i.e., significantly different responses to words vs. pseudofonts) neural activity is isolated through frequency-tagging. Critically, this sensitive approach allows to objectively quantify category-selective neural responses and disentangle them from general visual responses. About 70% of significant contacts show either only face-selectivity or only word-selectivity, with the expected right and left hemispheric dominance, respectively. Spatial dissociations are also found within core regions of face and word processing, with a medio-lateral dissociation in the fusiform gyrus (FG) and surrounding sulci, while a postero-anterior dissociation is found in the inferior occipital gyrus (IOG). Only 30% of the significant contacts show both face- and word-selective responses. Critically, in these contacts, across the VOTC or in the FG and surrounding sulci, between-category selective-amplitudes (faces vs. words) showed no-to-weak correlations, despite strong correlations in both the within-category selective amplitudes (face-face, word-word) and the general visual responses to words and faces. Overall, we conclude that category-selectivity for faces and written words is largely dissociated in the human VOTC. Significance StatementIn modern human societies, faces and written words have become arguably the most significant stimuli of the visual environment. Despite extensive research in neuropsychology, electroencephalography and neuroimaging over the past three decades, whether these two types of visual signals are recognized by similar or dissociated processes and neural networks remains unclear. Here we provide an original contribution to this outstanding scientific issue by directly comparing frequency-tagged face- and word-selective neural responses in a large group of epileptic patients implanted with intracerebral electrodes covering the ventral occipito-temporal cortex. While general visual responses to words and faces show significant overlap, the respective category-selective responses are neatly dissociated in spatial location and magnitude, pointing to largely dissociated processes and neural networks.

neuroscience↗

bioRxiv2017

A Face Identity Hallucination (Palinopsia) Generated By Intracerebral Stimulation Of The Face-Selective Right Lateral Fusiform Cortex

We report the case of a patient (MB, young female human subject) who systematically experiences confusion between perceived facial identities when electrically stimulated inside the lateral section of the right fusiform gyrus. In the presence of a face stimulus (an experimenter or a photograph), intracerebral electrical stimulation in this region generates a perceptual hallucination of an individual facial part integrated within the whole perceived face, i.e. facial palinopsia. In the presence of a distracting stimulus (visual scene or object picture), the patient also experiences an individual face percept superimposed on the non-face stimulus. The stimulation site evoking this category-selective transient palinopsia is localized in a region showing highly selective responses to faces both with functional magnetic resonance imaging (\"Fusiform Face Area\", \"FFA\") and intracerebral electrophysiological recordings during fast periodic visual stimulation (FPVS). Importantly, the largest electrophysiological response to fast periodic changes of facial identity is also found at this location. Altogether, these observations suggest that a local face-selective region of the right lateral fusiform gyrus suffices to generate a vivid percept of an individual face, supporting the active role of this region in individual face representation.

neuroscience↗