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 CO(2) 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 (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.

RESULTS: 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.