Behavior of olfactory-related frontal lobe oscillations in Alzheimer's disease and MCI: A pilot study

Slow-gamma (35-45 Hz) phase synchronization and the coupling between slow-gamma and low-frequency theta oscillations (4–8 Hz) are closely related to memory retrieval and cognitive functions. In this pilot study, we assess the Phase Amplitude Coupling (PAC) between theta and slow-gamma oscillatory bands and the quality of synchronization in slow-gamma oscillations using Phase Locking Value (PLV) on EEG data from healthy individuals and patients diagnosed with amnestic Mild Cognitive Impairment (aMCI) and Alzheimer's Disease (AD) during an oddball olfactory task. Our study indicates noticeable differences between the PLV and PAC values corresponding to olfactory stimulation in the three groups of participants. These differences can help explain the underlying processes involved in these cognitive disorders and the differences between aMCI and AD patients in performing cognitive tasks. Our study also proposes a diagnosis method for aMCI through comparing the brain's response characteristics during olfactory stimulation and rest. Early diagnosis of aMCI can potentially lead to its timely treatment and prevention from progression to AD. •An oddball olfactory experiment was conducted on a cohort of healthy elderly and amnestic MCI and AD patients.•Indicators of spatial coherence and cross-frequency coupling in the oscillatory activity of the brain were extracted.•These indicators were proposed as topographical markers of aMCI and AD.•Network-level markers can complement other biomarkers based on behavioral, molecular, genetic, or structural assessment.•Differentiating aMCI status from normal and AD states allows for early intervention to decelerate its progress to AD.