Subcortical dysfunction in schizophrenia: a comparison with Parkinson's disease and Huntington's disease.

Neuropsychological performance in 20 chronic schizophrenic patients was contrasted to 25 Parkinson's disease, 12 Huntington's disease patients and 26 normal controls on measures shown to be sensitive to subcortical dysfunction. Some overlap was observed in the performance of the schizophrenic and basal ganglia groups on tasks of executive and mnestic function, but the general pattern indicated significant differences in performance. Notably, in contrast to the two basal ganglia groups, there was no evidence of slowed thinking, or impaired motor function in schizophrenia, which are considered hallmarks of subcortical grey matter disease. An association was observed between poor performance on the tests of executive function and the severity of negative symptoms. Our findings suggest that schizophrenia is not associated with primary subcortical impairment, but is more likely to reflect frontotemporal dysfunction. We consider that the similarities between this disorder and subcortical degenerative syndromes may be due to a difficulty in generating action in schizophrenia, perhaps arising from dorsolateral prefrontal disconnection.