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Michel, C.

Publications and source records attributed to Michel, C..

2 recordsLinked to original sources

Does force-field adaptation induce after-effects on space representation?

Prism adaptation is a well-known model to study sensorimotor adaptive processes. It has been shown that following prism exposure, after-effects are not only restricted to the sensorimotor level but extend as well into spatial cognition. The main purpose of the present study was to investigate in healthy individuals whether expansion to spatial cognition is restricted to adaptive processes peculiar to prism adaptation or whether it occurs as well following other forms of adaptive process such as adaptation to a novel dynamic environment during pointing movements. Representational after-effects were assessed by the perceptual line bisection task before and after adaptation to a leftward or a rightward force field. The main results showed that adaptation developed at sensorimotor level but did not produce after-effects in space representation. However appropriate analysis showed that the slower a participant de-adapt to a rightward dynamic perturbation, the stronger the influence on the perceptual midline judgment during the late phase of the bisection task. The discussion highlights the commonalities between prism and dynamic adaptation on the effects on space representation.

neuroscience

Gating by induced α-γ asynchrony in selective attention

Visual selective attention operates through top-down mechanisms of signal enhancement and suppression, mediated by -band oscillations. The effects of such top-down signals on local processing in primary visual cortex (V1) remain poorly understood. In the present work, we characterize the interplay between large-scale interactions and local activity changes in V1 that orchestrates selective attention, using Granger-causality and phase-amplitude coupling (PAC) analysis of EEG source signals. The task required participants to either attend to or ignore oriented gratings. Results from time-varying, directed connectivity analysis revealed frequency specific effects of attentional selection: bottom-up {gamma}-band influences from visual areas increased rapidly in response to attended stimuli while distributed top-down -band influences originated from parietal cortex in response to ignored stimuli. Importantly, the results revealed a critical interplay between top-down parietal signals and -{gamma} PAC in visual areas. Parietal -band influences disrupted the -{gamma} coupling in visual cortex, which in turn reduced the amount of {gamma}-band outflow from visual areas. Our results are a first demonstration of how directed interactions affect cross-frequency coupling in downstream areas depending on task demands. These findings suggest that parietal cortex realizes selective attention by disrupting cross-frequency coupling at target regions, which prevents them from propagating task-irrelevant information.

neuroscience