Motor memory and the preselection effect in Huntington's and Parkinson's disease.

Patients with Huntington's disease (HD) and Parkinson's disease (PD) show different patterns of preserved and impaired memory performance. This study investigates explicit memory for movements in HD and PD with a linear positioning apparatus using Dick et al.'s procedure (J. Gerontol. 43, 127-135, 1988). In the first experiment, 12 HD patients were compared to 12 matched-controls. HD patients were more impaired than the controls by the delay between criterion and recall movements, whether the delay was filled or unfilled. Switching the limb between criterion and recall movements did not lead to more effects in HD patients and in controls. In the second experiment, 12 non-demented PD patients were compared to matched-controls. PD patients were more impaired than controls when the recall movement was executed with the contralateral hand, but were not more affected by the delay. In both experiments, HD and PD patients, as well as the controls, recalled self-generated preselected movements better than imposed movements. These results suggest the existence of distinct forms of motor memory impairment in some subcortical neurodegenerative diseases.