Cognitive speed in nondemented Parkinson's disease

Studies of speed of cognitive processing in Parkinson's disease (PD) have y ielded mixed results. This may relate in part to a differential effect on c ognitive speed by the type of information to be processed. In the present s tudy, we compared medication fasted, nondemented individuals with mild idio pathic PD (N = 26) with age-matched controls (N = 12) on a test requiring e asy and hard same-different discriminations for verbal, quantitative, and s patial information, as well as on a traditional memory scanning paradigm. A voice-activated relay rather than a key press was used to eliminate the ne ed for limb and finger movements. Simple reaction time and movement time we re also measured in a task requiring subjects to move a hand held stylus to a designated target. The PD group performed as fast as the control group a cross all tasks except movement time. Thus, in our paradigm, the presence o f PD alone does not predict cognitive slowing in the presence of motor slow ing.