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

Conclusion: 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 CO2 stimulation is due to a phenomenon known as trigeminal sensitization during repeated stimulation. Objectives: 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. Subjects and methods: Ten normosmic healthy subjects participated this study. Phenyl ethyl alcohol (PEA), hydrogen sulphide (H2S) and carbon dioxide (CO2) 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. Results: The amplitudes of CSERPs with PEA and H2S 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 CO2. The ANOVA revealed a significantly different effect of shortening the ISI on CSERPs on the right and the left side.