Activation of respiratory afferents by resistive loaded breathing modifies somatosensory evoked potentials to median nerve stimulation in humans

The cortical projections of respiratory afferents (vagus and respiratory muscle nerves) are well documented in humans. It is also shown that their activation during loaded breathing modifies the perception of tactile sensation as well as the motor drive to skeletal muscles. The effects of expiratory or inspiratory loaded breathing on somatosensory evoked potentials (SEPs) elicited by median nerve stimulation were studied in eight healthy subjects. No significant changes occurred in latencies of N20, N30 and P40 throughout the expiratory loading period, except for a significant lengthening in P1 latency compared with unloaded breathing. However, inspiratory loading induced a significant increase in peak latency of N20, N30 and P40 components. We suggest that projections of inspiratory afferents from the diaphragm and the intercostal muscles, activated by inspiratory loading, could be responsible for the lengthened latency of median nerve SEP components. Thus, respiratory afferents very likely interact with pathways of the somatosensory system.