Lexical decision in Parkinson disease: lack of evidence for generalized bradyphrenia

Twenty-two nondemented patients with idiopathic Parkinson disease (PD) and 22 controls completed a lexical decision task for which the expected relationship between primes and targets was manipulated. Both reaction times and movement times were measured. PD subjects were as effective as controls in utilizing the priming cues to reduce their reaction times compared with a neutral condition. This facilitation occurred even at the shortest stimulus onset asynchrony employed (300 ms), and was observed in a condition requiring a shift of attention, suggesting that PD patients experience no general cognitive slowing and no difficulty efficiently shifting attention to a specified semantic category. The degree of facilitation was significantly greater in the PD group in several comparisons, indicating hyperpriming. Finally, expectancy primes facilitated movement times in the PD group only. Although the results do not support the existence of generalized bradyphrenia in nondemented Parkinson disease, the hyperpriming effect and correlational analyses involving vocabulary scores and choice reaction time do raise the possibility of a subtle semantic processing deficit or an impairment of strategic decision-making in PD.