Cortical motor reorganization in akinetic patients with Parkinson's disease

Using functional MRI (fMRI), we have studied the changes induced by the of a complex sequential motor task in the cortical areas of six patients with Parkinson's disease and six normal subjects. Compared with normal subjects, the patients with Parkinson's disease exhibited a relatively fMRI signal in the rostral part of the supplementary motor area (SMA) in the right dorsolateral prefrontal cortex, as previously shown in PET. Concomitantly, the same patients exhibited a significant bilateral increase in fMRI signal in the primary sensorimotor cortex, lateral cortex, inferior parietal cortex, caudal part of the SMA and anterior cortex. These fMRI data confirm that the frontal hypoactivation in patients with Parkinson's disease is restricted to the rostral part the SMA and to the dorsolateral prefrontal cortex. These results also show, apart from the lateral premotor and parietal cortices, increased fMRI can be found in other cortical motor areas of these patients, including posterior SMA, the anterior cingulate cortex and the primary sensorimotor, which are then likely to participate in the same putative attempt by dopamine-denervated brain to recruit parallel motor circuits in order to the functional deficit of the striatocortical motor loops.