Initiation and execution of movement sequences in those suffering from and at-risk of developing Huntington's disease.

Recent research has shown that Huntington's disease (HD) causes problems in the initiation and execution of movement (akinesia, bradykinesia): information which is useful in documenting the functional progression of the disease. The present experiment used a sequential movement task to characterize such impairments. Eighteen patients diagnosed as suffering from HD, and a similar number of matched At-Risk (AR) and Normal control subjects, performed sequential button pressing tasks, under varying amounts of visual advance information. Specific dimensions of motor control were examined (hand, direction). Movement initiation and in particular movement duration were useful indicators of the functional progression of the disease, and also detected anomalies of performance in some AR individuals. Impaired motor programming was indicated by patients' difficulty in initiating movements in the absence of external visual cues, and their problems in utilizing advance information to control movement. Patients had specific deficits in initiating movements with the nonpreferred hand, and directional movement asymmetries were accentuated. The results suggest that HD causes difficulties at three discrete levels: in utilizing advance information, in the initiation and in the spatial representation of movement.