ABSTRACT
The term “psychosis” has a checkered history. It fi rst appeared in the nineteenth century, implying a “mental” disorder, in contrast to the older term “neurosis,” which implied organic disorder of the brain. Today, in the English-speaking world these two terms have almost completely reversed their respective original meanings. Psychosis is held to have a physical basis in the brain, whether or not that is known. The term, as commonly understood, means that patients suffer “a break with reality.” In other words, psychosis is a state characterized by delusions and hallucinations. There are many sorts of psychosis, some with clear evidence of an organic lesion, some without such evidence, but presumably involving dynamic disturbance of brain activity. Psychosis is not generally classed as one of the disorders of the basal ganglia. Usually, it is considered as one of the manifestations of schizophrenia. It may even be regarded as synonymous with schizophrenia. This complex disorder involves disturbed activity in most structures of the forebrain, although there is no clear focal lesion. However, there are many abnormalities in schizophrenia-mainly enduring traits*—other than psychosis, which is a transient state. Psychosis also occurs in bipolar disorder, as mania, whose underlying basis is not well defi ned, but has some overlap with schizophrenia.
