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Modulation du traitement cortical des informations visuelles et somatosensorielles en situation d’incongruence: une approche électroencéphalographique

Abstract : Since Woodworth (1899), vision is well recognized by the scientific community to be of a great importance to control voluntary movements. Besides, we know that somatosensory information is also essential for that purpose, as shown by works largely initiated by Sherrington at the beginning of the last century. However, the literature provides little information about the neural mechanisms underlying the processing of visual and somatosensory information during voluntary movements. The goal of our doctoral research was to better understand how the brain integrates visual and somatosensory information during the control of movement. More specifically, we investigated the weighting of these sensory inputs in conditions under which they provided either congruent or incongruent information about hand motion. A visuo-somatosensory incongruence arises in our day-to-day life, for example, when we wear eyeglasses or when we use a computer mouse for the first time. It can also be induced experimentally, as we have done in our experiments, by shifting the visual feedback of the environment with a mirror or a computer device. In experimental paradigms that provided either congruent or incongruent visual and somatosensory information, we asked participants to follow precisely the outline of an irregular shape with a stylus on a digitizing tablet. Brain activity was recorded with an electroencephalographic device, and quantified by measuring visual evoked potentials amplitudes [Study 1], and the power in the alpha (8-12 Hz), beta (15- v 25 Hz) and gamma (50-80 Hz) frequency-bands [Studies 2 and 3]. We first evidenced that visually-guided hand movements increased the sensitivity to visual inputs of a large cortical network. Moreover, we showed that controlling movement in a situation with an incongruence between visual and somatosensory input led to a further increase of visual, somatosensory and posterior-parietal cortical excitability. We suggest that these modulations reflect sensory weighting mechanisms in order to attempt to adapt to the sensory incongruence. Interestingly, in the somatosensory areas, we found that the sensory incongruent condition led to a reduction of gamma power, suggesting a reduced integration of somatosensory inputs for controlling movements which might have attenuated the sensory incongruence. Finally, we reported that motor learning (or over-learning) in a task without sensory incongruence and visuomotor adaptation in a task with sensory incongruence both resulted in a reduced activity of the posterior occipital and right posterior parietal cortices. Taken together, our findings are in line with the existence of a general sensory gain control mechanism driven by the state of adaptation of the sensorimotor system in a given sensory context. More generally, our results argue for the idea that sensory processing is function of the context-dependent relevance of the sensory inputs.
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https://hal-amu.archives-ouvertes.fr/tel-01461448
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Submitted on : Wednesday, February 8, 2017 - 10:53:09 AM
Last modification on : Tuesday, October 20, 2020 - 3:10:35 AM
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Nicolas Lebar. Modulation du traitement cortical des informations visuelles et somatosensorielles en situation d’incongruence: une approche électroencéphalographique. Neurosciences. Aix Marseille Université, 2016. Français. ⟨tel-01461448⟩

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