Electroencephalographic predictors of olfactory stimulus discrimination in COVID-19 survivors

OBJECTIVE: To analyze the spectral characteristics of electroencephalogram (EEG) activity during an olfactory discrimination test. MATERIAL AND METHODS: The study involved 26 COVID-19 survivors with a reported history of anosmia. Participants were exposed to three types of odorants using a diffuser. EEG recordings were obtained while waiting for and during stimulus presentation. Based on their performance, participants were divided into two groups, and EEG power in the delta, theta, alpha, and beta frequency ranges was analyzed. RESULTS: The findings indicated that greater delta and theta activity during the odor expectation phase correlated with successful discrimination. Conversely, higher beta activity was associated with an increased number of errors. Participants demonstrating high recognition accuracy also had shorter mean reaction times. A negative correlation was identified between delta rhythm power and the number of errors made. CONCLUSIONS: EEG spectral scores can serve as neurophysiological indicators of sensory efficiency in olfactory tests. Notably, some patients may display subtle disturbances in brain activity even without overt symptoms. These findings are significant for the diagnosis and personalized rehabilitation of post-COVID conditions, including the development of neurological feedback methods and olfactory training.