NOT JUST THE SAME OLD THING: CORTICAL AND AUTONOMIC MEASURES OF AFFECTIVE HABITUATION

Habituation can be defined as a learning process where the initial orienting response elicited by a significant stimulus decreases following repeated exposure. Several studies have shown that emotional pictures are effective cues in activating an orienting response. In two studies, we examined the effects of picture repetition on affective modulation of autonomic and cortical responses. In line with previous studies, autonomic responses were expected to rapidly habituate as a function of picture repetition, but little was known about ERP affective habituation. It was hypothesized that if the early posterior negativity (150 – 300 ms) is sensitive to processing relevant perceptual features of affective pictures, even a high number of repetitions of the same picture should not affect the early ERP modulation. On the contrary, if the late positive potential (300 – 600 ms) reflects a higher level of attentional involvement, affective modulation is expected to decrease with stimulus repetition. Results indicated that autonomic responses rapidly habituated after a few repetitions, probably because no adaptive action is necessary. On the other hand, ERP data showed that, despite a high number of picture repetitions, the brain continued to differentially respond to emotional and neutral pictures at both early and late stages in the processing stream. Although stimulus repetition generally decreased the late positive potential, affective stimuli continued to elicit larger late potentials than did neutral stimuli, suggesting continued allocation of greater attentional resources.