An automatic-voluntary dissociation and mental imagery disturbance following a cerebellar lesion

The cerebellum receives signals from, and sends signals to, the parietal cortex and instances of cerebellocerebral diaschisis indicate that some behaviours are controlled through this circuitry. Not all aspects of action control associated with the parietal cortex have been reported in patients with cerebellar damage though. Presented here is a case study of a cerebellar patient whose action deficits appear to be associated with both cerebellar and parietal functions. AM was 27 years old and eight years previously he had an operation to remove a cystic cerebellar tumour. He was tested on his ability to carry out motor imagery, make instructed and spontaneous actions, and intrinsic and extrinsic movements. Similar to ideomotor apraxia patients AM showed an automatic-voluntary dissociation where his motor control was better on spontaneous actions than instructed ones. He also had poor motor imagery timing. However, unlike apraxia patients he was equally poor at controlling body-related and object-related actions and his performance improved without vision. The presence of problems more commonly associated with parietal cortex functions suggest that the cerebellum is involved in a broader spectrum of action abilities than previously thought.