Event-related Slow Potentials Research Articles

The effect of warning interval on signal detection and event-related slow potentials of the brain

The amplitude of a slow potential wave in the EEG was examined during performance of a signal detection task under several fixed intervals between warning signal and critical signal. It was observed that the probability of detecting the critical signal decreased as the interval increased, and that this effect was due to a change in sensitivity rather than a change in criterion. The time-course of the change in sensitivity was related to that of the slow potential wave, which peaks shortly after the warning signal and then declines over a period of several seconds, and is interpreted as a component of the orienting response. It is suggested that the mechanism whose function is reflected in this wave also accounts for some effects of foreperiod duration and warning signal characteristics in reaction time tasks.

Slow cerebral potentials in psychiatry

Classical electroencephalography has brought no major contribution to psychiatric diagnosis over the last 40 years. However, new hopes have recently arisen with the introduction of new methods — the use of long-time constants together with averagers and/or computers. Cerebral electrogenesis is explored during a more or less complex task, for instance pushing a button following a visual or auditory stimulus. The amplitude and duration of potentials preceding and following the decision and the motor activity are recorded. Many of the workers have attempted to establish psychological correlations of phenomena such as the CNV (contingent negative variation or expectancy wave) (8) and RP (readiness potential, pre-motor potential) (5). The cerebral events immediately following the decision and motor action PINV, (post imperative negative variations) are studied. These are considered to be of special interest in psychiatric patients. A minority of normal subjects (16 percent) show what is described as abnormalities of these potentials, whereas the majority of psychotics (75 percent) show these abnormalities. Neurotic patients show an intermediary percentage of abnormalities (37 percent). In early schizophrenia, abnormal PINV are present in 94 percent of the cases, which makes the test of practical significance in doubtful cases. Studies of event-related slow potentials in more complex situations, with discriminative decisions requested from the subjests, are underway.