Respiration phase dependent modulation of somatosensory evoked potentials.

The respiration phase (inhalation vs. exhalation) has been shown to influence behavioral variables such as action execution, perception, and cognition, possibly due to interactions between the breathing cycle and higher cortical functions. However, whether somatosensory processing differs between inhalation and exhalation remains unclear. The aim of this study was to investigate the effects of respiration phase on somatosensory evoked potentials (SEPs) in healthy individuals. While simultaneously recording high-density electroencephalography and respiratory signals during normal breathing, electrical stimulation was applied to the median nerve at the right wrist during both inhalation and exhalation phases in twenty subjects. The amplitude of the P200 component was significantly greater during exhalation than during inhalation, whereas no significant effects of respiration phase were observed for earlier SEP components (N20, P20, P22, N27, P27, N30, P45, N60, and P100). The difference in SEP amplitude between the two respiration phases gradually increased over the epoch period. These findings indicate that somatosensory processing fluctuates in phase with the respiratory cycle.