Modulation of the ERP repetition effects during exposure to phobia-relevant and other affective pictures in spider phobia.

In the present study, dense sensor event-related potentials were measured in spider-phobic individuals and non-anxious controls during incidental encoding of phobia-relevant spider and standard neutral, unpleasant and pleasant pictures. Stimulus repetition effects were assessed by presenting each picture twice--in the first and in the second half of the session. Repeated presentation of standard pleasant, unpleasant and neutral pictures resulted in a late ERP repetition effect that was similarly pronounced in both experimental groups and for all picture categories. Moreover, relative to non-fearful controls spider-phobic individuals showed an overall greater early ERP repetition effect starting at 180 ms after picture onset. At later stages of evaluative processing, repeated as compared with initial presentation of phobia-relevant spider pictures elicited reduced ERP amplitudes over centro-parietal sites (480-580 ms) in spider-phobic but not in control individuals. This pattern of results indicates that in small animal phobics long lasting exposure to their feared pictures leads to an increased mobilization of the perceptual analysis system, an effect that might help to improve emotional control and/or facilitate strategic avoidance of threat resulting in a diminished evaluative threat processing. This phobia-specific processing mechanism might prevent effective stimulus processing and hinder the habituation process during treatment.