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.
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- "Wilmut et al.  tested the effect of producing saccades on the accuracy of sequential pointing and concluded that the role of ocular proprioception was far less important than the role of the feedforward system that is activated when an eye movement is initiated. Van Donkelaar et al.  provided even more direct evidence. The influence of decorrelating eye and hand movement start points (see Section 1) on hand movement amplitude is significantly reduced by transcranial magnetic stimulation over the posterior parietal cortex when stimulation is delivered 0–100 ms prior to saccade onset. "
ABSTRACT: Execution of a saccadic eye movement towards the goal of a hand pointing movement improves the accuracy of this hand movement. Still controversial is the role of extra-retinal signals, i.e. efference copy of the saccadic command and/or ocular proprioception, in the definition of the hand pointing target. We report here that hand pointing movements produced without visual feedback, with accompanying saccades and towards a target extinguished at saccade onset, were modified after gain change of reactive saccades through saccadic adaptation. As we have previously shown that the adaptation of reactive saccades does not influence the target representations that are common to the eye and the hand motor sub-systems (Cotti J, Guillaume A, Alahyane N, Pelisson D, Vercher JL. Adaptation of voluntary saccades, but not of reactive saccades. Transfers to hand pointing movements. J Neurophysiol 2007;98:602-12), the results of the present study demonstrate that extra-retinal signals participate in defining the target of hand pointing movements.Behavioural brain research 03/2011; 218(1):248-52. DOI:10.1016/j.bbr.2010.12.002 · 3.39 Impact Factor
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- "Finally, also the spatial pattern of the observed TMS effects (impact on the aIPS and aSMG but not on more posterior control sites) argues against putative TMS effects on saccades as a large body of literature shows that more posterior parts of the PPC are involved in saccade processing (Simon et al. 2002; Konen et al. 2004). The TMS studies in this field always tested more posterior positions compared with our sites and offer inconsistent results on whether left PPC TMS does affect saccades processing (Van Donkelaar et al. 2000; Yang and Kapoula 2004). Desmurget et al. (1999) were the only group to date demonstrating that TMS over the left IPS largely disturbed online corrections in a visually perturbed reaching paradigm. "
ABSTRACT: The posterior parietal cortex (PPC) plays an important role in controlling voluntary movements by continuously integrating sensory information about body state and the environment. We tested which subregions of the PPC contribute to the processing of target- and body-related visual information while reaching for an object, using a reaching paradigm with 2 types of visual perturbation: displacement of the visual target and displacement of the visual feedback about the hand position. Initially, functional magnetic resonance imaging (fMRI) was used to localize putative target areas involved in online corrections of movements in response to perturbations. The causal contribution of these areas to online correction was tested in subsequent neuronavigated transcranial magnetic stimulation (TMS) experiments. Robust TMS effects occurred at distinct anatomical sites along the anterior intraparietal sulcus (aIPS) and the anterior part of the supramarginal gyrus for both perturbations. TMS over neighboring sites did not affect online control. Our results support the hypothesis that the aIPS is more generally involved in visually guided control of movements, independent of body effectors and nature of the visual information. Furthermore, they suggest that the human network of PPC subregions controlling goal-directed visuomotor processes extends more inferiorly than previously thought. Our results also point toward a good spatial specificity of the TMS effects.Cerebral Cortex 11/2010; 21(7):1602-12. DOI:10.1093/cercor/bhq225 · 8.67 Impact Factor
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- "De son côté, la main droite tire de ses liens directs avec l'hémisphère gauche un autre type d'avantage qui s'exprime mieux avec un sabre : elle est plus apte à un contrôle continu de la trajectoire du membre au cours de son déroulement  . Le cortex pariétal postérieur gauche semble jouer un rôle de « pilote automatique » pour la main droite  . Il s'agit d'un véritable contrôle « en ligne ». "
ABSTRACT: Duel sports, such as fencing, boxing and table-tennis, like some “face-to-face” individuals in team sports, give rise to extremely fast visuo-motor interactions. These situations, characterized by a high level of uncertainty in space and time, require a very high level of visual attention from protagonists. Investigations carried out in these sports reveal, at the highest level of world ranking, an over-representation of manual left-handers, the majority of them having a right ocular dominance. Right-handers having a left dominant eye are also represented at a relatively high-rate. Experimental tasks with spatio-temporal uncertainty implemented in the laboratory have made it possible to confirm a visuo-motor advantage, in response time, in subjects having an eye–hand crossed laterality.Science & Sports 12/2008; 23(6):263-277. DOI:10.1016/j.scispo.2008.06.004 · 0.54 Impact Factor