Midlatency respiratory-related somatosensory activity and perception of oral pressure pulses in normal humans

A direct relationship exists within subjects between midlatency features (< 100 ms poststimulus) of respiratory-related evoked potentials and the perce ived magnitude of applied oral pressure pulse stimuli. We evaluated percept ion in 18 normal subjects using cross-modality matching of applied pressure pulses via grip force and estimated mechanoafferent activity in these subj ects by computing the global field power (GFP) from respiratory-related evo ked potentials recorded over the right side of the scalp. We compared acros s subjects 1) the predicted magnitude production for a standard pressure pu lse and 2) the slope (<beta>) and 3) the intercept (INT) of the Stevens pow er law to the summed GFP over 20-100 ms poststimulus. Both the magnitude pr oduction for a standard pressure pulse and the b showed an inverse relation ship with the summed GFP over 20-100 ms poststimulus, although there was no relationship between INT and the summed GFP. This may partially reflect ch aracteristics of the mechanosensors and surely includes aspects of cognitiv e judgment, because we found and corrected for a high correlation between, respectively, b (and INT) for pressure pulses and b (and INT) for estimatio n of line lengths, a nonrespiratory modality. The relatively shallow, even inverse GFP-to-perception relationship suggests that, despite marked differ ences in the magnitude of afferent traffic, normal subjects seem to perceiv e things similarly.