Stimulus-Induced Narrowband Gamma Oscillations are Test–Retest Reliable in Human EEG

Abstract

Visual stimulus-induced gamma oscillations in electroencephalogram (EEG) recordings have been recently shown to be compromised in subjects with preclinical Alzheimer’s Disease (AD), suggesting that gamma could be an inexpensive biomarker for AD diagnosis provided its characteristics remain consistent across multiple recordings. Previous magnetoencephalography studies in young subjects have reported consistent gamma power over recordings separated by a few weeks to months. Here, we assessed the consistency of stimulus-induced slow (20–35 Hz) and fast gamma (36–66 Hz) oscillations in subjects (n = 40) (age: 50–88 years) in EEG recordings separated by a year, and tested the consistency in the magnitude of gamma power, its temporal evolution and spectral profile. Gamma had distinct spectral/temporal characteristics across subjects, which remained consistent across recordings (average intraclass correlation of ~ 0.7). Alpha (8–12 Hz) and steady-state-visually-evoked-potentials (SSVEPs) were also reliable. We further tested how EEG features can be used to identify two recordings as belonging to the same versus different subjects and found high classifier performance (AUC of ~ 0.89), with temporal evolution of slow gamma and spectral profile being most informative. These results suggest that EEG gamma oscillations are reliable across sessions separated over long durations and can also be a potential tool for subject identification.

Slope of the power spectral density flattens at low frequencies (<150 Hz) with healthy aging but also steepens at higher frequency (>200 Hz) in human electroencephalogram

“…Further, any new outlier if it belonged to the visual electrodes or was common in more than 10% of other electrodes was considered a bad repeat and appended to the existing list of bad repeats. This led to rejection of additional 1.24 ± 1.72 electrodes and 0.16 ± 1.05% repeats. This condition was added mainly to improve power spectral density (PSD) plots unlike the previous studies (Murty et al, 2020, 2021; Kumar et al, 2022) that dealt mainly with change in power. The main results remained similar even without applying this new criterion. We further discarded the blocks which did not have at least a single good unipolar electrode in the left visual anterolateral (P3, P1, PO3, O1), right visual anterolateral (P2, P4, PO4, O2) and posteromedial (POz, Oz) electrode groups.…”

“…The details of experimental setup and data collection have been explained in detail in previous studies (Murty et al, 2020(Murty et al, , 2021Kumar et al, 2022); here, we summarize them briefly.…”

“…This led to rejection of additional 1.24 േ 1.72 electrodes and 0.16 േ 1.05% repeats. This condition was added mainly to improve power spectral density (PSD) plots unlike the previous studies (Murty et al, 2020(Murty et al, , 2021Kumar et al, 2022) that dealt mainly with change in power. The main results remained similar even without applying this new criterion.…”

“…Inc; RRID:SCR_001622). Similar to the previous studies (Murty et al, 2020(Murty et al, , 2021Kumar et al, 2022) on this dataset, we chose [−500 0] ms as the eyes open period, yielding a resolution of 2 Hz. The analyses were performed using unipolar reference scheme, unless otherwise specified.…”

“…FCz and Fpz were used as the reference and the ground respectively. In our previous studies (Murty et al, 2020(Murty et al, , 2021Kumar et al, 2022), power analysis was done on electrodes for which strong gamma power was observed (P3, P1, P2, PO3, POz, PO4, O1, Oz and O2), which were termed as "high priority" electrodes. We performed slope analysis on this group as well.…”