Late event-related potentials and psychopathology.

Event-related potentials include not only the short duration evoked potentials (EPs) associated with sensory stimulation or motor response but also longer duration potentials such as the contingent negative variation, for which the eliciting events are more complex. For EPs there seems to be a relationship between the latency of the EP component and the degree of influence by more cognitive psychological variables such as attention. In general, the "early" sensory EP components occurring before 50 msec are least sensitive to these variables, components between 50 and 200 msec are affected to an intermediate extent, and the components after 200 msec are the most susceptible to psychological influence. Conversely, the earlier components are most dependent on stimulus modality and other physical parameters of the stimuli. Although early EP components might be better for reflecting the more enduring features of psychiatric disorders—a biological substrate for schizophrenia, for example—since they are less influenced by fluctuations in mental state, it is important to realize that psychiatric disorders are not known to alter sensation in its primary aspects. If there are characteristic psychological manifestations of these disorders, these manifestations would be more likely to influence the later components of the EP or other event-related potentials. Both sides of this argument are represented in psychopathology and event-related potential research today: Some investigators study the early EP components in hopes of finding a central biological deficit in schizo-