Interaction of electro-ocular potentials with the contingent negative variation.

Abstract

ABSTRACTThe contingent negative variation (CNV) was recorded from the vertex in forty‐five subjects during a two‐stimulus expectancy paradigm under varying conditions of eye closure and fixation. Simultaneously averaged electro‐oculograms (EOG) were recorded as a measure of eye movement. The amplitude of both CNV and EOG responses was significantly greater for the eyes closed and eyes open unfixated conditions as compared to the eyes fixated condition. CNV and EOG responses were often highly similar in terms of waveform. For the eyes fixated condition three patterns of CNV–EOG interaction were observed. Eighteen subjects demonstrated a CNV response of low amplitude in the absence of detectable EOG responses. Twenty‐three subjects showed a predominant pattern in which CNV responses of high amplitude and EOG responses were present. Four subjects failed to show either a CNV or EOG response. There was considerable within subject variability in the pattern of response with replicated blocks of trials. Thus contamination of the CNV by EOG potentials is reduced by eye fixation but not eliminated because of subject variability in control of eye movement.