tokens: We have studied the regional cerebral blood flow ( rCBF ) changes induced by the execution of a finger - to - thumb opposition motor task in the supplementary and primary motor cortex of two groups of parkinsonian patients on L-dopa medication , the first one without L-dopa induced dyskinesia ( n = 23 ) and the other with moderate peak - dose dyskinesia ( n = 15 ), and of a group of 14 normal subjects .