Speed and power of higher cerebral functions in parkinsonian patients.

We compared 21 idiopathic, pharmaceutically well managed parkinsonian patients, neurological stages I and II on the Hoehn and Yahr scale with 21 parkinsonian patients stage III and 19 healthy controls group-matched for age, sex and education to study to what extent impairments of fluid intelligence in parkinsonian patients are due to a slowing of cognitive processes, i.e. to bradyphrenia (a deficit in the speed component) or to a true performance deficit (a deficit in the power component). The Vienna Matrices Test, which is similar to Raven's Standard Progressive Matrices was presented to the patients in a modified form. The Cognitrone was used to measure the influence of vigilance and perception on the cerebral function assessed. With increasing neurological severity of the disease, the dimension examined showed true deficits in the power component. There was no bradyphrenia in the sense of slower performance which would otherwise be equal to that of the control subjects. Vigilance and perception did not change in the course of the disease.