High speed memory scanning in parkinsonism.

This study tested the hypothesis that the slowing seen in parkinsonism includes cognitive as well as motoric components. The sample consisted of 20 nondemented parkinsonian patients, group matched to 16 normals by age, education, and verbal IQ. Each group was divided into young (64 and under) and old (65 and over) subsets. The Sternberg character classification paradigm was used to measure the speed and accuracy of one cognitive function, short term memory scanning. Following a logarithmic transformation of the reaction time data, scanning speed was found to be increased, but only for the elderly patients (p = .01). Scanning accuracy was normal for both patient groups. These findings suggest that at least one cognitive function, the scanning of elements held in short term memory, is slowed in parkinsonism. This mnemonic slowing, like bradykinesia, is seen primarily in elderly parkinsonian patients. It is not readily explained as a motor phenomenon, as part of a generalized mnemonic or intellectual deficit, or as an artifact secondary to periodic extreme reaction times. The term bradyphrenia, used in early descriptions of parkinsonism, may be an apt descriptor of this deficit.