Cortical evoked potentials and behavioral reactivity to photic stimuli in freely moving rats

Averaged evoked potentials at the visual cortex (VER) were studied in relation to behavioral reactivity to photic stimuli during operant behavior for food reinforcement. The VERs showed highly systematic increases in late components with repetition of the sensory stimuli. Amplitude of late components related inversely to behavioral indices of reactivity, but the correlations between these measures were low to moderate. Control experiments involving other freely moving and curarized animals served to evaluate various behavioral and stimulus factors in the VER changes. The results were interpreted in terms of habituation of ‘arousal reactions’, for which additional supporting data were provided. Electrographic arousal, however, was viewed as a varying substrate of all behavior, which complicates relationships between VERs and any single index of behavioral reactivity to stimuli in freely moving subjects.