Deficits in sensorimotor control during precise hand movements in Huntington's disease

Objectives: To investigate the performance of patients with Huntington's di sease (HD) while manipulating objects using a precision grip. Methods: The grip forces developed by the fingers were studied while subjec ts lifted an object of unpredictable weight in the hand. The ability to sta bilize grip force after externally imposed weight change was also studied. Results: patients used higher grip forces than the normal subjects in both the lifting and holding phases, particularly with a lighter weight. Lift ti ming was slowed in the patients, most markedly with a lighter weight. Incre ased levels of inter-trial variation were observed only with a light weight . This indicates that the slowing in HD differs from that in Parkinson's di sease, which remains constant regardless of object load, and that the slowi ng in HD is not due to involuntary antagonist muscle activity resulting fro m an underlying chorea. The grip force response to sudden weight change was normal, but appeared after a delay which increased at lower rates of weigh t change. Conclusions: Disturbances in precision grip timing and magnitude in HD may result from a reduced ability to process relevant tactile afferent input. T he delay in the adaptive response suggests an increased threshold for detec tion of weight change in HD. Alternatively, this delay may arise from media tion of the response over an additional cerebellar pathway to compensate fo r damage to the basal ganglia. (C) 2001 Elsevier Science Ireland Ltd. All r ights reserved.