Abstract
This paper studies the procedural learning of semantic categorization in 29 patients with non-demented Parkinson's disease (PD). We investigated whether the PD group was able to develop semantic skill, using a cognitive procedural task developed in our laboratory, applying a manual and serial reaction time paradigm to semantic categorization. The PD group showed similar scores to those of the control group on semantic categorization. Both groups showed reaction time reduction over the semantic procedural task, but the PD group produced longer reaction times than the control subjects. Contrary to our prediction, we observed an improvement in semantic categorization reaction times with practice, even with new verbal material for the PD patients to categorize despite their motor impairments and executive deficits. By contrast, we found a significant negative correlation between axial motor signs and the ratio of semantic procedural learning, but not for lateral motor signs. The present results support the notion that non-demented PD patients may be capable of acquiring comparable semantic skill to those of the control group.