Cortical motor reorganization in akinetic patients with Parkinson's disease - A functional MRI study

Using functional MRI (fMRI), we have studied the changes induced by the per formance of a complex sequential motor task in the cortical areas of six ak inetic patients with Parkinson's disease and six normal subjects. Compared with the normal subjects, the patients with Parkinson's disease exhibited a relatively decreased fMRI signal in the rostral part of the supplementary motor area (SMA) and in the right dorsolateral prefrontal cortex, as previo usly shown in PET studies. Concomitantly, the same patients exhibited a sig nificant bilateral relative increase in fMRI signal in the primary sensorim otor cortex, lateral premotor cortex, inferior parietal cortex, caudal part of the SMA and anterior cingulate cortex. These fMRI data confirm that the frontal hypoactivation observed in patients with Parkinson's disease is re stricted to the rostral Dart of the SMA and to the dorsolateral prefrontal cortex, These results also show that, apart from the lateral premotor and p arietal cortices, increased fMRI signals can be found in other cortical mot or areas of these patients, including the posterior SMA, the anterior cingu late cortex and the primary sensorimotor cortices, which are then likely to participate in the same putative attempt by the dopamine-denervated brain to recruit parallel motor circuits in order to overcome the functional defi cit of the striatocortical motor loops.