Resting EEG partial coherence demonstrates increased γ range central functional connectivity in amnestic mild...

Relatively little is known about EEG high γ (gamma) range changes in Alzheimer's disease (AD). We investigated functional connectivity, focusing on the γ range, in amnestic Mild Cognitive Impairment (MCI) using ordinary Coherence (COH) and Partial Coherence (PCOH), a metric which enhances signal to noise ratio at high frequencies.

MCI (N=21) and Cognitively normal (CN, N=62) ALBION study participants had resting EEG with eyes closed (EC) and eyes open (EO) in 10/20 montage (19 active electrodes). COH and PCOH in 0.5-100 Hz for each subject were calculated for all 171 electrode pairs.

In both γ₁ (30-50 Hz) and γ₂ (50-100 Hz) ranges, PCOH was significantly higher in MCI than in CN in several electrode pairs, especially centrally, in both eye conditions. Concerning local (average of each electrode) connectivity, MCI compared to CN showed significantly higher values in PCOH centrally.

Resting EEG γ range functional connectivity at central areas, as revealed by PCOH, is significantly higher in MCI than in CN.

γ range local and regional EEG functional connectivity differences may help construct useful and easily available biomarkers in neurodegeneration. Metrics, such as PCOH, which factor out global connectivity components may help reveal such differences.