Effects of short inter-stimulus intervals on olfactory and trigeminal event-related potentials

Chemosensory event-related potentials (CSERPs) were identified in all measurements using the 20 s and the 10 s inter-stimulus interval (ISI) protocol, reducing the recording time to 75% or 57% compared with the standard protocol. A possible explanation for the rising CSERP amplitudes by shortening the ISI in CO(2) stimulation is due to a phenomenon known as trigeminal sensitization during repeated stimulation.

CSERPs are influenced by the ISI. The aim of this study was to evaluate the changes in CSERPs by decreasing the ISI from 30 s to 20 s or 10 s, respectively.

Ten normosmic healthy subjects participated this study. Phenyl ethyl alcohol (PEA), hydrogen sulphide (H(2)S) and carbon dioxide (CO(2)) were used in CSERP measurements with different ISI protocols (30 s (standard), 20 s and 10 s). Amplitudes and latencies of ISI protocols were submitted to ANOVA for repeated measurements and t tests for paired samples.

The amplitudes of CSERPs with PEA and H(2)S stimuli were decreasing with shortening the ISI significantly. In contrast, the highest amplitudes of trigeminal CSERPs were recorded with the 10 s ISI protocol with CO(2). The ANOVA revealed a significantly different effect of shortening the ISI on CSERPs on the right and the left side.