Phasic heart rate responses for anticipated threat situations

The effects of anticipated threat situations and the valence of the stimuli on the deceleration of the phasic heart rate (HR) were investigated in a single experiment using an S1–S2 paradigm. There were certain S1 cues that were always expected to be followed by neutral pictures (S2 stimuli), and uncertain S1 cues that had a 50% probability of being followed by neutral or unpleasant pictures (S2 stimuli). Greater phasic HR deceleration was observed for S2 stimuli following uncertain S1 cues than for S2 stimuli following certain S1 cues, regardless of the valence of the S2 stimuli. This result suggests that an anticipated threat situation in which participants anticipate facing potentially unpleasant stimuli leads to the allocation of more attentional resources. Additionally, correlation analyses revealed that highly anxious individuals tended to show greater HR deceleration in response to unpleasant stimuli, possibly reflecting maladaptive attentional bias for threat stimuli.