Международный журнал физической медицины и реабилитации
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Separate Pathways for Automatic and Intentional Visuo-Manual Reach Transformations: New Perspectives for Hemiparesia Rehabilitation Using Moving Objects

Pisella L, Gaveau V, Delporte L, Revol P, Prablanc C, Jacquin-Courtois S, Rode G, Luauté J and Rossetti Y

Reaching implies effector and target locations to be computed and updated continuously all along the visuo-motor transformation process, before and during movement execution, aiming in making these instantaneous locations coincide spatially. So instead of a neuro-anatomical dissociation between areas devoted to motor planning versus control, there might be 1) an automatic pathway of visual-to-motor transformation which relies on a comparison at the level of oculo-centric coordinates between visual target and hand locations from multimodal sources of information and 2) intentional pathways relying on the allocentric comparison between visual locations of the hand and of the target. Converging evidence from patients with optic ataxia, neuroimaging and transcranial magnetic stimulation techniques, and investigations in primates, has led to ascribe the automatic pathway to the direct connection between the medio-dorsal occipito-parietal cortex (the caudal part of the superior parietal lobule) and the dorsal premotor cortex (and further the primary motor cortex). Studies involving patients with visual agnosia (infero-temporal cortex), Parkinson disease (basal ganglia) or neglect (inferior parietal lobule) have put forward a more diffuse putative neural substrate for the intentional visual-to-motor pathway. If most strokes affect the intentional motor function while preserving the automatic pathway of visual-to-motor transformation, we propose a new rehabilitation method for hemiparesia relying on the stimulation of the automatic pathway using moving rather than stationary objects. Preliminary data are included.