The average evoked-potential waveforms to sound and light stimuli recorded from scalp in awake human subjects show differences as a function of the subject's degree of uncertainty with respect to the sensory modality of the stimulus to be presented. Differences are also found in the evoked potential as a function of whether or not the sensorymodality of the stimulus was anticipated correctly. The major waveform alteration is in the amplitude of a positive-going component which reaches peak amplitude at about 300 milliseconds.

No abstract

Although descriptive and etiological approaches to psychopathology have made notable advances, they seem to have reached a plateau. After reviewing the six approaches to etiology that now preempt the field-ecological, developmental, learning, genetic, internal environment, and neurophysiological models-a second-order model, vulnerability, is proposed as the common denominator, and methods for finding markers of vulnerability are suggested in the hope of revitalizing the field. It is assumed that exogenous and/or endogenous challengers elicit a crisis in all humans, but depending on the intensity of the elicited stress and the threshold for tolerating it, that is, one's vulnerability, the crisis will either be contained homeostatically or lead to an episode of disorder. Vulnerability and episode stand in a trait-state relation, and markers for each must be provided to distinguish between them.

The waveform of evoked responses recorded from human scalp is not determined solely by the physical eliciting stimulus, but also varies as a function of the effective information provided by the stimulus. There is a positive component whose latency is determined by the point in time at which ambiguity is reduced, and whose shape and amplitude are influenced by whether it is the presence or absence of an external event which delivers the information.