Respiratory mechanoreceptor activation of somatosensory cortex in humans

Humans can consciously perceive difficulty with their breathing. It is known that humans can sense external respiratory loads by peripheral mechanoreceptors and process the afferent information via several afferent pathways. However, neural pathways processing the conscious sensation of respiratory loads and how this respiratory afferent information projects to higher brain centers are still poorly understood.; The respiratory-related potential (RREP) elicited by inspiratory occlusion in humans recorded from the scalp provided a unique way to investigate the neural mechanisms mediating respiratory load information and the activation of mechanoreceptor related brain activity. The major goal of this dissertation was to investigate the activation of respiratory mechanoreceptor eliciting RREP responses to inspiratory loads and its relation to somatosensory cortical activation. Using somatosensory evoked potentials as a model of RREP processing, RREP responses to inspiratory occlusion and during breathing against inspiratory resistive loads with increased background resistance were studied in this dissertation.; The short-latency RREP components were compared with the components of the somatosensory evoked potential (SEP) elicited by mechanical stimulation of the hand, chest, and mouth. Short-latency components of the RREP were also compared between no-background resistance and increased background resistance to determine the mechanism of respiratory bowline state on afferents projecting to the cortex.; Three studies were conducted and a total of 6D healthy adults participated. Results from the first two studies demonstrated that the RREP and SEP are both observed over the somatosensory cortex. Unlike the SEP, the RREP appeared to be elicited by afferents that project simultaneously to both sides of the somatosensory cortex. The RREP may have greater amplitude due to greater population of afferents activated with a global stimulus such as inspiratory occlusion. These results further demonstrated that the RREP Nf peak is a unique frontal cortical activation elicited by inspiratory occlusion. The results from the third study demonstrated the RREP can be changed by increasing the background load and shifting the detection threshold of the subject. If the resistive load was detectable, the RREP will be present; if the load was not detectable or became undetectable with increased background load, the RREP was absent.