Moving with or without will: functional neural correlates of alien hand syndrome.

Alien hand syndrome is a rare neurological disorder in which movements are performed without conscious will. By using functional magnetic resonance imaging in a patient with alien hand syndrome after right parietal lesion, we could identify brain regions activated during involuntary or voluntary actions with the affected left hand. Alien hand movements involved a selective activation of contralateral primary motor cortex (M1), presumably released from conscious control by intentional planning systems. By contrast, voluntary movements activated a distributed network implicating not only the contralateral right M1 and premotor cortex but also the left inferior frontal gyrus, suggesting an important role of the dominant hemisphere in organizing willed actions.