Contingent negative variation and the distraction--arousal hypothesis.

Thirty-two normal volunteers were tested in three conditions: (1) a constant-foreperiod reaction-time situation consisting of a flash--tone--key-press sequence (control condition); (2) the addition of a short-term memory task consisting of four letters presented within the flash--tone interval with the requirement that they be repeated after key-press to tone (letters--recall); (3) the presentation of letters without short-term memory (letters--no recall). The task involving short-term memory of letters produced a significant reduction in amplitude of CNV for central (Cz) and parietal (Pz) recording sites. The association of CNV decrease and lengthened reaction time to tone was interpreted as a CNV distraction effect. The accompaniment of this distraction effect by elevated heart rate levels and increased frequency of eyeblinks was considered a distraction--arousal association and an important source of disruption in CNV development. These results were interpreted as support for the distraction--arousal hypothesis and appear to provide a sensitive complex of four measures for the evaluation of psychological processes, including the assessment of psychotropic drug effects. Eyeblink frequency in particular appears to be a sensitive indicator of distraction--arousal processes and a potentially useful measure of disturbed psychological functioning. The finding in control conditions of lower CNV amplitude in frontal than in central and posterior recording sites was viewed as a distraction effect due to efforts at eye movement control. The possibility was raised that frontal areas of the brain mediate sustained (tonic) distraction effects whereas centro-parietal regions mediate phasic distraction effects, at least when produced by stimuli of a lexical nature.