[The mental state of parkinsonian patients].

The systematic study of cognitive functions in parkinsonian patients has demonstrated specific disturbances of memory, visuo-spatial function and frontal lobe activity. Global impairment of intellectual functions is less common (it occurs in 15 to 20 percent of the cases) and is observed mainly in elderly patients. Dementia differs in its neuropsychological set up from that of Alzheimer's disease. The most frequent psychiatric disorders are depressive state, signs of anxiety and side-effects of drugs, including visual hallucinations and confusion. This means that some of these drugs (e.g. anticholinergics, dopaminergic agonists) should be prescribed with extreme caution in elderly people and in those who show signs of intellectual degradation. The mental disorders of Parkinson's disease are of interest because of their frequency and pathogenesis: the principal lesions of the disease are located in subcortical structures, which calls for elucidation of the role played by these structures in the organization of affective and cognitive behaviours. For this reason, Parkinson's disease is a very good model for the study of such interactions.