Psychophysiological responses to inspiratory resistive loads.

Fear of interoceptive sensations is relevant for a number of psychiatric and somatic disorders. Pappens et al. (2010, Biol. Psychol. 84, 98-103) reported elevated skin conductance responses (SCR), subjective fear, and a paradoxical lack of startle potentiation during aversive respiratory stimulation with an inspiratory resistive load (IRL). This study aimed to replicate these findings and to explore whether the lack of startle potentiation during an aversive IRL is related to attentional allocation to the IRL. Reaction times to the acoustic startle probe served as an indirect index of attentional focus on the respiratory stimulus. The earlier findings on SCR and subjective fear were replicated. However, startle potentiation occurred for the aversive IRL with a 1500 ms lead interval, and reaction times to the acoustic probe were not slower for the aversive IRL compared to other types of lead stimuli. This suggests that startle potentiation during aversive respiratory stimulation with IRLs only occurs when an exteroceptive task limits attentional allocation to the interoceptive experience.