Prominent gamma band activity during visual motion perception in early-stage Alzheimer’s disease

Abstract

Introduction Alzheimer’s disease (AD) affects multiple neural pathways and regions, resulting in various visual impairments such as motion perception. Generally, gamma-band activities during visual motion perception have been thought to reflect ongoing cognitive processes. Nevertheless, few studies have specifically examined induced gamma band activity during visual motion perception in AD patients. Therefore, after performing magnetoencephalography (MEG) recording during apparent motion (AM) stimulation for the left hemi-visual field in patients diagnosed as having AD in the early stage, we compared the results with findings of cognitive performance. Methods Seventeen AD patients in the early stage and 17 controls matched for age, sex, and educational attainment participated in this study. For each participant, memory performance was assessed with the Mini-Mental State Examination (MMSE) and the Wechsler Memory Scale-Revised (WMS-R). For MEG analysis, we examined power changes induced in a higher frequency range (20–100 Hz) after AM stimuli. Results The power of induced gamma band activities was significantly higher in AD patients. The power of induced gamma band activities was associated with higher performance on both MMSE and WMS-R tests for attention and concentration in AD patients. Conclusions Given that neuronal dysfunction in AD is associated with excitotoxic neurodegeneration, and given that subsequent development of compensatory inhibitory mechanisms also contributes to pathology in AD patients, elevated gamma band oscillations might reflect an imbalance of inhibitory and excitatory activity in AD patients. Moreover, positive correlation between induced gamma activity and cognitive performance might signify a compensating mechanism of inhibitory neurons which preserve the pyramidal neuron from excitotoxicity in a posterior association area.

Eyes-state-dependent alterations of magnetoencephalographic connectivity associated with delayed recall in Alzheimer’s disease via graph theory approach

“…The participants in the current study partially overlapped with those in our previous research ( 53 ); however, none of the results presented in this study overlapped with the findings of the previous research. Moreover, the focus and objectives of the previous study were distinct from those of the current study.…”

“…MEG and MRI recording protocols followed those established in our previous study ( 53 ). All the participants underwent two MEG recording sessions, each lasting 2 min, under different conditions: EO and EC.…”

Multiple cross-frequency coupling analysis of resting-state EEG in patients with mild cognitive impairment and Alzheimer’s disease

“…Therefore, the increase of theta rhythm in our study may be an early phenomenon of neurodegeneration that reflects memory deficits of AD patients. Moreover, gamma oscillations are linked to higherorder cognitive functions including information processing (Fries et al, 2008;Leicht et al, 2021), perception (Melloni et al, 2007;Naito et al, 2022), attention (Jensen et al, 2007;Magazzini and Singh, 2018), and memory (Kucewicz et al, 2017). A study of more than 300 individuals by Gaubert et al (2019) explored the effects of AD neurodegeneration and amyloid-deposition on EEG metrics, they found a non-linear relationship between amyloid burden and EEG metrics, following a U-shape curve for gamma power, where patients' gamma power decreased as amyloid load exceeded a certain threshold.…”