Contingent negative variation: components and scalp distribution in psychiatric patients.

Components and scalp distribution of the contingent negative variation (CNV) were studied in various diagnostic groups (DSM III): normals, opioid-dependent subjects, alcohol-dependent subjects, neurotics, schizotypics, nonschizophrenic psychotics, and schizophrenics. A principal components analysis revealed four late slow waves: early and late CNV and early and late postimperative negative variation (PINV) waves. The late CNV wave appeared a better indicator of psychopathology than early CNV or PINV, but the amplitude difference between central and frontal CNV seems at least of equal importance. This is mainly due to the late CNV component. The psychopathological correlates of this amplitude difference seem characterized by two mutually interacting dimensions: a general psychopathology dimension which correlates with relatively high frontal CNV, and a negative schizophreniform symptomatology dimension which correlates with relatively low frontal CNV. Substance-dependent subjects were more closely related to normals than to psychiatric patients regarding CNV variables. Hemispheric asymmetry of the CNV was not significantly related to psychiatric diagnosis.