To evaluate clinically the slowing of cognitive processing in Parkinson's disease, we used a visual discrimination task consisting of 15 superimposed images of objects. The time needed to identify 12 objects increased by 58% in 70 patients withdrawn from levodopa treatment compared with 20 controls matched for age and education. Perceptual, motor, and psycholinguistic factors, as well as mood, only partially accounted for the slowness of performance. The 15-objects test scores of the parkinsonian patients correlated significantly with both their intellectual impairment and the severity of their parkinsonian disability, but not with the duration of the disease. The scores did not correlate with depression. Levodopa had no effect on the score, although the parkinsonian motor disability score was improved by 54%. The results indicate a cognitive slowing in Parkinson's disease which is probably related to abnormalities of nondopaminergic neuronal systems in the brain.

SUMMARY Seven patients with Parkinson's disease and severe motor fluctuations were studied with event-related potentials, reaction and movement times and neuropsychological tests while in "off' and "on" phases. While there was a significant decrement in the P300 latency of the event-related potentials and in the duration ofmovement time in the "on" phase, no significant differences between on and off phases were observed in reaction time and neuropsychological tasks.

ABSTRACT:Vigabatrin (ɣ-vinyl GABA; GVG), an irreversible inhibitor of GABA-transaminase, at a daily dose of 2-4 g, and a placebo were each administered orally for 4 months to 14 patients with cerebellar ataxia (9 with Friedreich's ataxia, 5 with olivopontocerebellar atrophy), in a double-blind, placebo-controlled crossover study. For the group as a whole, there was no significant difference between the GVG and placebo periods in any of the parameters of cerebellar symptomatology measured. Individually, one patient showed some improvement after 3 months of treatment with 2 g/day GVG. Tolerance to 4 g/day GVG was poor, whereas 2 g/day was well tolerated. The results suggest that agents which increase central GABA concentrations are not likely to be of benefit to patients with Friedreich's ataxia or olivopontocerebellar atrophy.

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