MOTOR PROGRAM MEMORY STORAGE IN PARKINSONS-DISEASE PATIENTS TESTED WITH A DELAYED-RESPONSE TASK

We used a delayed response paradigm to test the hypothesis that the pr olonged reaction time in patients with Parkinson's disease (PD) is rel ated to a deficiency in their ability to store a motor program in memo ry while waiting to move. PD patients, both on and off medication, wer e compared with age-matched normal subjects during arm movements direc ted toward a target light. The target light was displayed either durin g a 3- to 9-s delay or for only 1 s followed by a 2- to 8-s delay befo re the go signal. At the end of the delay, subjects were required to b egin movement rapidly. The reaction time of PD patients was longer tha n normal and increased slightly when the patients were off medication. The patients had no excessive increase in reaction time with delay in either task compared with the control subjects. We conclude that pati ents with PD can hold a motor program in memory storage for at least 8 s.