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.

Neuropsychological performance in lateralized parkinsonism.

Seven dextral patients with Parkinson's disease (PD) who had predominant right-sided motor signs were compared on neuropsychological tests with eight dextral patients with PD who had predominant left-sided signs. Objective criteria for group designation were developed from clinical ratings. The patient subgroups were matched on age, education, estimated premorbid IQ, severity of motor signs, and medication usage. Patients with signs lateralized to the right were more impaired on tests of dominant hemisphere function (serial digit learning, confrontation naming, and verbal associative fluency), but no differences were found on tests of nondominant hemisphere function (form sequence learning, line orientation, facial recognition), indicating some correlation of neuropsychological performance with lateralization of predominant motor signs. Findings demonstrate that the cognitive deficits (particularly visuospatial) previously reported in the literature are not seen consistently in all subjects with PD.