Effects of cardiac and respiratory phases on auditory evoked potentials

Brain-body interactions play a crucial role in the perceptual and cognitive processing of external stimuli. Previous research has examined how cardiac phases (systole, diastole) and respiratory phases (inhalation, exhalation) influence various psychological functions, though findings on their impact on auditory processing remain inconsistent. This study investigated whether cardiac and respiratory phases affect auditory ERP components, specifically N1 and P2. To control for cardiac-related artifacts, pure tones (70 dB) and silent stimuli (0 dB) were presented in alternating, randomized intervals, and ERP difference waveforms were computed by subtracting waveforms elicited by silent stimuli from those elicited by tones. Two experiments were conducted with different participants: watching a video while ignoring the tones (Experiment 1) or pressing a button as quickly as possible in response to the tones while watching the video (Experiment 2). Results showed no significant differences in N1 amplitude between cardiac or respiratory phases. P2 amplitude was significantly larger at diastole than systole, although the effect size was small (d_z = 0.26). For respiratory phases, P2 amplitude was greater during exhalation than inhalation when participants ignored the tones (d_z = 0.35), but this effect disappeared when they attended to the tones. These findings suggest that visceral afferent signals may influence auditory processing by modulating attentional resource allocation across different cardiac and respiratory phases.