“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 SD, 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 SD 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 SD 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.