“Contingent Negative Variation” in Rhesus Monkeys: An EEG Sign of a Specific Mental Process

Abstract

Utilizing long time-constant EEG recording techniques, magnetic tape storage, and electronic averaging, the phenomenon designated the “contingent negative variation” or “expectancy wave” was studied in 3 Rhesus monkeys. Three basic conditioning paradigms were used: escape conditioning with a warning cue, discrimination task with aversive reinforcement following S^D, and discrimination with appetitive reinforcement. Trials were presented in blocks of 12 and averaged on line with an Enhancetron electronic averager. In each case, during acquisition trials, a surface negative slow potential gradually developed only following the evoked response to S^D and preceding the meaningful stimulus. No shift followed the unreinforced stimulus. During extinction trials, the shift gradually diminished. During discrimination reversal, a negative shift developed following the previously unreinforced stimulus, while the shift following what had been S^D gradually diminished. Results demonstrate the appearance of the “contingent negative variation” in these monkeys and support the contention that this shift is a result of cerebral electrical activity during conation.