The middle evoked response components and schizophrenia

Abstract

In a subject sitting quietly without a specific task, the largest evoked potential (EP) components are the middle three: a positive, negative, positive sequence occurring at 50-100, 110-140, and 160-200 milliseconds. These components, termed P100, N140, and P200 in this review, were initially observed in the raw EEG in a few subjects before the advent of signal averaging (Davis 1939). The now widespread agreement that the N140 peak is a correlate of selective attention and the many findings relating P200 to habituation and/or novelty effects - all psychological phenomena possibly associated with deficits in schizophrenia - recommend the study of these components. Other factors as well appear to make the study of these EP components especially suitable. Perceptual and cognitive abnormalities in schizophrenics are not specific to one sensory modality; and while P100 seems to occur earlier with auditory than visual stimuli, N140 and P200 have very similar configurations across auditory, visual, and somatosensory stimuli when recorded at vertex (which generally yields the largest amplitudes as well). The size and frequency of the components make them somewhat more immune to artifacts of eye movement, myogenic components, muscle contamination, or electronic interference than early or late components.