Chemosensory event-related potentials to trigeminal stimuli change in relation to the interval between repetitive stimulation of the nasal mucosa

Event-related potentials (ERPs) to olfactory and trigeminal stimuli have be en used commonly to evaluate chemosensory dysfunction. The aim of the prese nt study was to investigate how ERPs could be modified by repetitive stimul ations of the intranasal trigeminal nerve using 52% v/v CO2 stimuli for 200 ms periods. Nine subjects were exposed to 6 sessions each during which tra ins of 16 stimuli were applied. The interval between stimuli was constant f or each experiment, but varied between experiments (10, 20, 30, 40, 60, and 90 s). Trigeminal ERPs were obtained from three positions on the skull. Bo th intensity ratings and ERP amplitudes decreased as the interstimulus inte rval (ISI) shortened. Specifically, ratings and response amplitudes were mo st strongly reduced by approximately 30-50% at the shortest ISI used (10 s) and were largest at an ISI of 90 s. The decrease of amplitudes was stronge st for the P-46 amplitude. Our findings suggest that this may be the result of both habituation and stimulus predictability. We hypothesize that the I SI dependence of chemosensory ERPs may also be a function of an interaction between A(delta) and C fibers.