Biology subjects

Bontemps, B.

Publications and source records attributed to Bontemps, B..

4 recordsLinked to original sources

bioRxiv2025

Multi-task Intracranial EEG recordings reveal a Comprehensive Role of the Human Dorsal Anterior Insula in High-Level Cognition

The dorsal anterior insula (dAI) is widely recognized as a cornerstone of human cognition. However, its functional characterization remains the subject of considerable debate and competing theories. Embracing a "shift in viewpoint" approach--defining a brain regions function through the observation of the same neural population across diverse experimental contexts--this study used intracranial EEG (iEEG) recordings from a large cohort of patients to investigate the sub-second neural response dynamics of the human dAI across a broad range of cognitive tasks, spanning visual category discrimination, phonological and semantic processing, attentive visual search, and verbal and visuospatial working memory. This within-subject, multi-task iEEG framework offered a robust basis for decoding the structure-function relationship of the dAI and for empirically testing key predictions of prevailing theoretical models concerning its role. Our findings confirmed the dAIs involvement in the Action-Mode Network and shed new light on the large-scale spatiotemporal organization of that network, while providing novel insights into the interplay between cognitive effort and efficiency.

neuroscience↗

bioRxiv2025

The Inferior Frontal Sulcus, not the Anterior Insula, acts as a late-stage attentional gate for the fast rejection of salient but irrelevant sensory inputs during cognitive tasks

The ability to prioritize behaviorally relevant stimuli is essential for efficient cognition, particularly in distracting environments. The anterior insula (AI), a key node of the salience network, has been proposed to support this selection process by detecting salient events. A similar function, however, has also been attributed to the inferior frontal sulcus (IFS), located at the intersection of the ventral and dorsal attention networks. Here, we directly compared the respective contributions of these regions to attentional gatekeeping--the identification and rejection of attention-grabbing yet task-irrelevant "false positives" to preserve cognitive resources. We recorded intracranial EEG from 63 patients performing an attentive reading task designed to dissociate salience from task relevance. High-Frequency Activity (HFA) responses between 50 Hz and 150 Hz revealed that the IFS was the only region--across an extensive sampling of the frontal and insular cortices--to exhibit consistent, subsecond response dynamics compatible with the filtering of false positives. In contrast, the AI did not participate in the analysis or rejection of distractors and showed only sparse, delayed responses to targets, suggesting a role in coordinating or energizing downstream cognitive or motor processes rather than in salience detection per se. These findings indicate that the IFS--rather than the AI--is the primary late-stage node for attentional gatekeeping during cognitive tasks performed under distracting conditions.

neuroscience↗

bioRxiv2025

Diurnal Modulation of Persistent Inward Current Contribution to Spinal Motor Neuron Behaviour

Despite the critical role of persistent inward currents (PICs) in modulating motor neuron output, and thus neuromuscular performance, it remains unknown whether their contribution to motor neuron discharge behaviour varies throughout the day. This study aimed to determine whether PIC-related effects on motor neuron activity during submaximal dorsiflexion tasks differ between the early morning and late afternoon. Eighteen healthy adults (4 females; 27.4{+/-}5.6 years) performed triangular isometric contractions at two time-points: early morning (7:00-8:30 a.m.) and late afternoon (5:00-7:30 p.m.). Two conditions were tested: (1) a relative condition, where the target force corresponded to 40% of the maximal voluntary force (MVF) measured during that session, and (2) an absolute condition, where the target force was 40% of the MVF recorded during the first session. High-density surface electromyography signals were recorded from the tibialis anterior and decomposed into motor unit spike trains. The prolongation effect of PICs, estimated via {Delta}F, was significantly greater in the late afternoon in both the relative and absolute force conditions. The amplification effect of PICs, estimated by the acceleration phase of the discharge trajectory, was also higher in the late afternoon, but only in the relative force condition. No time-of-day differences were found for brace height, while attenuation was reduced in the late afternoon in the relative force condition. Collectively, these findings provide evidence for a diurnal modulation of the influence of PICs on motor neuron discharge behaviour, likely mediated by reduced inhibitory input in the late afternoon rather than by changes in neuromodulatory drive. Key pointsO_LI- Human neuromuscular performance fluctuates throughout the day, with higher force output typically observed in the late afternoon. C_LIO_LI- While circadian effects on peripheral determinants of muscle function (e.g., muscle- tendon properties, metabolic efficiency) are well documented, the neural mechanisms underlying these diurnal variations remain poorly understood. C_LIO_LI- Persistent inward currents (PICs) play a critical role in regulating motor neuron behaviour, yet their potential diurnal modulation has not been previously investigated. C_LIO_LI- Our results provide novel evidence for a diurnal modulation of the influence of PICs on motor neuron discharge behaviour, likely mediated by reduced inhibitory input in the late afternoon rather than by changes in neuromodulatory drive. C_LIO_LI- These findings suggest that intrinsic motor neuron excitability (and therefore spinal gain modulation) fluctuates across the day. C_LI

neuroscience↗

bioRxiv2020

THE DUAL-TASK COST IS DUE TO NEURAL INTERFERENCES DISRUPTING THE OPTIMAL SPATIO-TEMPORAL DYNAMICS OF THE COMPETING TASKS

Dual-tasking is extremely prominent nowadays, despite ample evidence that it comes with a performance cost: the Dual-Task (DT) cost. Neuroimaging studies have established that tasks are more likely to interfere if they rely on common brain regions, but the precise neural origin of the DT cost has proven elusive so far, mostly because fMRI does not record neural activity directly and cannot reveal the key effect of timing, and how the spatio-temporal neural dynamics of the tasks coincide. Recently, DT electrophysiological studies in monkeys have recorded neural populations shared by the two tasks with millisecond precision to provide a much finer understanding of the origin of the DT cost. We used a similar approach in humans, with intracranial EEG, to assess the neural origin of the DT cost in a particularly challenging naturalistic paradigm which required accurate motor responses to frequent visual stimuli (task T1) and the retrieval of information from long-term memory (task T2), as when answering passengers questions while driving. We found that T2 elicited neuroelectric interferences in the gamma-band (>40 Hz), in key regions of the T1 network including the Multiple Demand Network. They reproduced the effect of disruptive electrocortical stimulations to create a situation of dynamical incompatibility, which might explain the DT cost. Yet, participants were able to flexibly adapt their strategy to minimize interference, and most surprisingly, reduce the reliance of T1 on key regions of the executive control network - the anterior insula and the dorsal anterior cingulate cortex - with no performance decrement. HIGHLIGHTS- First direct evidence in humans of neural interferences between two tasks. - First explanation of the Dual-Task cost at the neural level in humans. - First Dual-Tasking study with intracranial EEG in naturalistic conditions.

neuroscience↗