Triggered by your heart: Effects of cardioafferent traffic and stress on automatic responses in a Simon task.

Variations in cardioafferent traffic are relayed to the brain via arterial baroreceptors and have been shown to modulate perceptual processing. However, less is known about the cognitive-behavioral consequences of these effects and their role during stress. Here, we investigated in how far automatic responses during the Simon task were modulated by exposure to a laboratory stressor and the different phases of the cardiac cycle. In this study, 30 participants performed three blocks of a combined horizontal and vertical Simon task, which is characterized by either sensorimotor or cognitive response conflicts, respectively. Before each block, subjects were exposed to both the cold pressor test (CPT) and a control condition according to a within-subjects design. Target stimuli were presented during either systole or diastole. Behavioral and EEG-correlates of task processing were assessed along with subjective, cardiovascular, and endocrine measures of stress. The stress induction was successful yielding significant increases in all these measures compared to control. Moreover, we found the expected Simon effects: in incompatible compared to compatible trials performance was decreased and LRP latency as well as anterior N2 area increased. Importantly, accuracy was improved in compatible but reduced in incompatible trials during systole vs. diastole but only in the horizontal Simon condition. Stress dampened N2 area, however, no interactions with cardiac cycle were evident. These results indicate a faciliatory effect of cardioafferent traffic on automated sensorimotor processes.