Arousal and Habituation Effects (Excitability) on Startle Responses to the International Affective Picture Systems (IAPS)

Abstract

The magnitude and habituation of startle reflex responses have been used to evaluate the excitability of the neural structures involved in this psychophysiological response. We analyzed the magnitude and habituation responses to startle reflex probes in 112 women. Results confirmed the modulation of eyeblink reflex by affective valence for arousing (F = 34.79, p < .001), but not for nonarousing pictures (F = 1.08, ns). Our results indicate that there is a linear adjustment for habituation in all picture groups, except for arousing unpleasant pictures where there is a quadratic adjustment that could be due to initial sensitization followed by the subsequent habituation. Multiple linear regression analysis revealed that the startle magnitude was partially determined by arousal and startle presentation order. In conclusion, our results emphasize the usefulness of arousing pictures to study startle reflex response and show evidence of different response mechanisms for pleasant and unpleasant pictures conditions.