Subregion-specific temporal lobe EEG signatures in amnestic mild cognitive impairment: Evidence from high-density EEG.

BackgroundAmnestic mild cognitive impairment (aMCI), a prodromal stage associated with an increased risk of Alzheimer's disease (AD), is characterized by early neural network dysfunction. The temporal lobe is among the earliest affected regions, yet conventional electroencephalography (EEG) provides limited information regarding subregional electrophysiological alterations.ObjectiveTo characterize temporal-subregional electrophysiological features in aMCI using high-density EEG (HD-EEG).MethodsFifty-five individuals with aMCI and 35 cognitively normal controls underwent neuropsychological assessment and resting-state 128-channel HD-EEG recording. Spectral power was quantified across the whole temporal lobe and its anterior, middle, and posterior subregions. Group differences were assessed using Welch's t-tests and Mann-Whitney U tests. Associations between EEG measures and cognitive performance were examined using Spearman correlation analyses. Exploratory receiver operating characteristic (ROC) and multivariable classification analyses were performed to evaluate discriminatory performance.ResultsCompared with controls, individuals with aMCI showed significantly poorer cognitive performance. HD-EEG analyses revealed increased gamma-band activity across bilateral temporal subregions, whereas elevated delta power and theta/beta ratios were primarily localized to right temporal subregions. Right temporal delta activity was negatively associated with memory performance. Connectivity analyses demonstrated enhanced fast-frequency coupling involving temporal regions, with particularly evident alterations in the left posterior temporal subregion. Classification analyses showed that gamma-band measures derived from left temporal subregions achieved discriminatory performance comparable to conventional whole-temporal measures.ConclusionsHD-EEG identified subregion-specific temporal-lobe electrophysiological alterations in aMCI. Temporal-subregional EEG profiling may provide additional electrophysiological information beyond conventional whole-lobe analyses and improve the characterization of aMCI-related neural alterations.