Motor imagery in normal subjects and in asymmetrical Parkinson's disease -A PET study

Objective To investigate, using PET and (H2O)-O-15, brain activation abnorm alities of patients with PD during motor imagery. To determine whether moto r imagery activation patterns depend on the hand used to complete the task. Background: Previous work in PD has shown that bradykinesia is associated with slowness of motor imagery. Methods: The PET study was performed in eig ht patients with PD with predominantly right-sided akinesia, and in eight a ge-matched control subjects, all right-handed. Regional cerebral blood flow was measured by PET and (H2O)-O-15 while subjects imagined a predetermined unimanual externally cued sequential movement with a joystick with either the left or the right hand, and during a rest condition. Results: In normal subjects, the prefrontal cortex, supplementary motor area (SMA), superior parietal lobe, inferior frontal gyrus, and cerebellum were activated during motor imagery with either the left or the right hand. Contralateral primar y motor cortex activation was noted only when the task was imagined with th e right (dominant) hand, whereas activation of the dorsolateral prefrontal cortex was observed only during imagery with the left hand. In patients wit h PD, motor imagery with the right ("akinetic") hand was characterized by l ack of activation of the contralateral primary sensorimotor cortex and the cerebellum, persistent activation of the SMA, and bilateral activation of t he superior parietal cortex. Motor imagery with the left ("non-akinetic") h and was also abnormal, with lack of activation of the SMA compared with con trols. Conclusions: In patients with PD with predominantly right-sided akin esia, brain activation during motor imagery is abnormal and may appear even with the less affected hand. In normal subjects, brain activation during m otor imagery depends on the hand used in the imagined movement.