THE PERCEPTION OF MOVEMENTS ELICITED BY MAGNETIC CORTEX STIMULATION DEPENDS ON THE SITE OF STIMULATION

Previous reports suggest that magnetic cortical stimulation (MCS) of t he motor cortex can elicit a sensation of movement (kinaesthesia) in p aralysed limbs. To assess this sensory effect of MCS, we examined the accuracy of kinaesthetic perception of stimulus-induced right elbow fl exion in six blindfolded, healthy subjects. Matching of movements elic ited by MCS was compared with matching of passive elbow movements. Sma ll flexion movements between 1.5 and 5 degrees of angle were regularly overestimated by 50-100% when induced by MCS over the parietal cortex , whereas movements elicited by MCS over the frontal cortex or by pass ive elbow flexion were accurately estimated. Our results provide data compatible with the hypothesis of the existence of a ''central sense o f movement''. Activation of collateral branches projecting from the mo tor cortex to the sensory could be the underlying mechanism to this ph enomenon.