Defense reactions to interoceptive threats: a comparison between loaded breathing and aversive picture viewing.

Human fear research has mostly applied exteroceptive stimuli to induce fear. Interoceptive sensations however can also be very threatening and play a major role in a number of anxiety disorders. In this study, we compared affective responses to inspiratory resistive loads with those to aversive pictures. During repeated administrations of two loads, a light and a moderate one, and five aversive pictures we measured electrodermal activity, startle blink responses, subjective fear and ratings on valence, arousal and dominance. Results indicate that loads evoke affective reactions comparable or stronger than those evoked by the pictures. Startle data did not follow this pattern with an absence of startle potentiation during the moderate load, suggesting that fear potentiated startle does not occur when the background aversive stimulus is of an interoceptive nature.