Transcranial magnetic stimulation disrupts eye-hand interactions in the posterior parietal cortex.
ABSTRACT Recent neurophysiological studies have started to shed some light on the cortical areas that contribute to eye-hand coordination. In the present study we investigated the role of the posterior parietal cortex (PPC) in this process in normal, healthy subjects. This was accomplished by delivering single pulses of transcranial magnetic stimulation (TMS) over the PPC to transiently disrupt the putative contribution of this area to the processing of information related to eye-hand coordination. Subjects made open-loop pointing movements accompanied by saccades of the same required amplitude or by saccades that were substantially larger. Without TMS the hand movement amplitude was influenced by the amplitude of the corresponding saccade; hand movements accompanied by larger saccades were larger than those accompanied by smaller saccades. When TMS was applied over the left PPC just prior to the onset of the saccade, a marked reduction in the saccadic influence on manual motor output was observed. TMS delivered at earlier or later periods during the response had no effect. Taken together, these data suggest that the PPC integrates signals related to saccade amplitude with limb movement information just prior to the onset of the saccade.
- European Neuropsychopharmacology - EUR NEUROPSYCHOPHARMACOL. 01/2011; 21.
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ABSTRACT: Modification or suppression of reaches occurs in everyday life. We argue that a common modular architecture, based on similar neural structures and principles of kinematic and kinetic control, is used for both direct reaches and for their on-line corrections. When a reach is corrected, both the pattern of neural activity in parietal, premotor and motor cortex and the muscle synergies associated with the first movement can be smoothly blended or sharply substituted into those associated with the second one. Premotor cortex provides the early signalling for trajectory updating, while parietal and motor cortex provide the fine-grained encoding of hand kinematics necessary to reshape the motor plan. The cortical contribution to the inhibitory control of reaching is supported by the activity of a network of frontal areas. Premotor cortex has been proposed as a key structure for reaching suppression. Consistent with this, lesions in different nodes of this network result in different forms of motor deficits, such as Optic Ataxia in parietal patients, and commission errors in frontal ones.Neuroscience & Biobehavioral Reviews 01/2014; · 10.28 Impact Factor
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ABSTRACT: When humans perform movements and receive on-line visual feedback about their performance, the spatial qualities of the visual information alter performance. The spatial qualities of visual information can be altered via the manipulation of visual gain and changes in visual gain lead to changes in force error. The current study used functional magnetic resonance imaging during a steady-state precision grip force task to examine how cortical and subcortical brain activity can change with visual gain induced changes in force error. Small increases in visual gain < 1° were associated with a substantial reduction in force error and a small increase in the spatial amplitude of visual feedback. These behavioral effects corresponded with an increase in activation bilaterally in V3 and V5 and in left primary motor cortex and left ventral premotor cortex. Large increases in visual gain > 1° were associated with a small change in force error and a large change in the spatial amplitude of visual feedback. These behavioral effects corresponded with increased activity bilaterally in dorsal and ventral premotor areas and right inferior parietal lobule. Finally, activity in the left and right lobule VI of the cerebellum and left and right putamen did not change with increases in visual gain. Together, these findings demonstrate that the visuomotor system does not respond uniformly to changes in the gain of visual feedback. Instead, specific regions of the visuomotor system selectively change in activity related to large changes in force error and large changes in the spatial amplitude of visual feedback.Journal of Neurophysiology 02/2010; 103(4):2114-23. · 3.30 Impact Factor