Clinical usefulness and feasibility of time-frequency analysis of chemosensory event-related potentials

Background:The Clinical usefulness of olfactory event-related:brain potentials (OERPs) to assess olfactory function is limited by the relatively low signal-to-noise ratio of the responses identified using conventional time-domain averaging. Recently, it was shown that time-frequency analysis of the obtained EEG signals can markedly improve the signal-to-noise ratio of OERPs in healthy controls, because It enhances both phase-locked and non phase-locked EEG responses.The aim of the present study was to investigate the clinical usefulness of this approach and evaluate its feasibility in a clinical setting. Methodology: We retrospectively analysed EEG recordings-obtained from 45 patients (15 anosmic, 15 hyposmic and 15 normosmic).The responses to olfactory stimulation were analysed using conventional time-domain analysis and joint time-frequency analysis.The ability of the two methods to discriminate between anosmic, hyposmic and normosmic patients was assessed-using a Receiver Operating Characteristic analysis. Results:The discrimination performance of OERPs identified using conventional time-domain averaging was poor. In contrast, the discrimination performance of the EEG response identified in the time-frequency domain was relatively high. Furthermore, we found a significant Correlation,between the magnitude of this response and the psychophysical olfactory score. Conclusion:Time-frequency analysis of the EEG responses to olfactory stimulation could be used as an effective and reliable diagnostic tool for the objective clinical evaluation of olfactory function in patients.