Increased EEG gamma band activity in Alzheimer’s disease and mild cognitive impairment

Abstract

High frequency (30-70 Hz) gamma band oscillations in the human electro-encephalogram (EEG) are thought to reflect perceptual and cognitive processes. It is therefore interesting to study these measures in cognitive impairment and dementia. To evaluate gamma band oscillations as a diagnostic biomarker in Alzheimer's disease (AD) and mild cognitive impairment (MCI), 15 psychoactive drug naïve AD patients, 20 MCI patients and 20 healthy controls participated in this study. Gamma band power (GBP) was measured in four conditions viz. resting state, music listening, story listening and visual stimulation. To evaluate test-retest reliability (TRR), subjects underwent a similar assessment one week after the first. The overall TRR was high. Elevated GBP was observed in AD when compared to MCI and control subjects in all conditions. The results suggest that elevated GBP is a reproducible and sensitive measure for cognitive dysfunction in AD in comparison with MCI and controls.

MEG spectral analysis in subtypes of mild cognitive impairment

“…Previous EEG (Babiloni et al 2004;Dauwels et al 2011;Huang et al 2000;Jeong 2004) and MEG studies (Berendse et al 2000;Fernandez et al 2002Fernandez et al , 2003Fernandez et al , 2006b) of AD found an increased power in the low-frequency bands (delta and theta), accompanied by a decreased power in the high-frequency range (alpha, beta, and gamma). Such pattern of spectral changes is a consistent finding that correlates with cognitive performance and functional status (Fernandez et al 2002;Prichep et al 1994;van Deursen et al 2008). …”

Neural synchrony and white matter variations in the human brain — Relation between evoked gamma frequency and corpus callosum morphology

“…Thus increased callosal white matter, which implies increased callosal myelination, reflects an enhanced facilitation of neural transmission und consequently facilitated and more efficient synchronization of neural activity between the two hemispheres. Interestingly, analogous correspondence between dysfunctional neural connectivity and altered oscillatory gamma activity has been reported in schizophrenia (Wilson et al, 2008;Herrmann and Demiralp, 2005;Lenz et al, 2011), as well as in Alzheimer's disease (He et al, 2009;van Deursen et al, 2008). However, so far the majority of these studies focused on the pathological related amplitudinal alterations of GBR.…”

Diagnosis of Alzheimers Disease from EEG Signals: Where Are We Standing?

“…One of the major effects is EEG "slowing"; many studies have shown that Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) causes EEG signals to slow down (see, e.g., [52,53,54,55,56,57,58,59,60,61,62,63,64,65]): MCI/AD is associated with an increase of power in low frequencies (delta and theta band, 0.5-8Hz) and a decrease of power in higher frequencies (alpha and beta, 8-30Hz). However, increased gamma band power (30-100Hz) has been reported in MCI/AD patients compared to healthy age-matched control subjects [67].…”