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Specificity of Human Parietal Saccade and Reach Regions during Transcranial Magnetic Stimulation| old_uid | 10126 |
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| title | Specificity of Human Parietal Saccade and Reach Regions during Transcranial Magnetic Stimulation |
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| start_date | 2011/07/18 |
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| schedule | 11h |
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| online | no |
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| location_info | Inserm, Salle de conférences |
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| details | Equipe Denis Pélisson "ImpAct - Integrative, Multisensory, Perception, Action and Cognition Team" |
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| summary | Single-unit recordings in macaque monkeys have identified effector-specific regions in posterior parietal cortex (PPC), but functional neuroimaging in the human has yielded controversial results.
Here we used on-line "event-related" repetitive transcranial magnetic stimulation (rTMS) to determine saccade and reach specificity in human PPC. A short train of three TMS pulses (separated by an interval of 100 ms) was delivered to superior parieto-occipital cortex (SPOC), a region over the midposterior intraparietal sulcus (mIPS), and a site close to caudal IPS situated over the angular gyrus (AG) during a brief memory interval while subjects planned either a saccade or reach with the left or right hand. Behavioral measures then were compared to controls without rTMS. Stimulation of mIPS and AG produced similar patterns: increased end-point variability for reaches and decreased saccade accuracy for contralateral targets. In contrast, stimulation of SPOC deviated reach end points toward visual fixation and had no effect on saccades. Contralateral-limb specificity was highest for AG and lowest for SPOC. Visual feedback of the hand negated rTMS-induced disruptions of the reach plan for mIPS and AG, but not SPOC. These results suggest that human SPOC is specialized for encoding retinally peripheral reach goals, whereas more anterior-lateral regions (mIPS and AG) along the IPS possess overlapping maps for saccade and reach planning and are more
closely involved in motor details (i.e., planning the reach vector for a specific hand). This work provides the first causal evidence for functional specificity of these parietal regions in healthy humans. Finally, based on these data, we propose a functional overview of human PPC regions involved in the planning and control of visuomotor action. |
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| responsibles | Béranger, Rossetti |
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