These findings lead to the hypothesis that reducing proprioceptive inflow to the brain improves performance in situations with a visuoproprioceptive conflict. Furthermore, in healthy persons who are adapting to a visuomotor transformation, movement accuracy correlates negatively with the firing activity of the muscle spindles ( Jones et al., 2001). In the absence of proprioception, it is easier to maintain movement speed and accuracy when the new mapping from the hand to the visual space is introduced ( Lajoie et al., 1992 Guedon et al., 1998). Intriguingly, performance deteriorates less in proprioceptively deafferented patients than in healthy controls when they change from normal to mirror drawing. In real life, for instance, it can happen to a surgeon who adjusts the view direction of the laparoscope to get a better view of the operation field or to a dentist who needs a mirror to work on the backside of the tooth. This problem arises when movements are visually monitored in a mirror or a video display and the performer has insufficient experience with the transformation from the hand to the visual space. It is thus possible, with rTMS, to enhance motor performance in tasks involving a visuoproprioceptive conflict, presumably by reducing the excitability of somatosensory cortical areas that contribute to the sense of hand position.Įxposure to a novel visuomotor spatial transformation results in an immediate decrease in movement accuracy ( Ghez et al., 2000). Using a position-matching task, we confirmed that rTMS reduced proprioceptive acuity and that this reduction was largest when the coil was placed at an anterior parietal site. Mirror tracing was more accurate after rTMS than after sham stimulation. Hand trajectory error during novel mirror drawing was compared across two groups of subjects that received either 1 Hz rTMS over the somatosensory cortex contralateral to the hand or sham stimulation. In this study, we tested whether deafferentation induced by repetitive transcranial magnetic stimulation (rTMS) can improve mirror tracing skills in normal subjects. ![]() ![]() Recent studies have shown that subjects without proprioception avoid this conflict and show a performance benefit. When performing visually guided actions under conditions of perturbed visual feedback, e.g., in a mirror or a video camera, there is a spatial conflict between visual and proprioceptive information.
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