Abnormalities of resting‐state eyes‐closed electroencephalographic rhythms are not affected by white matter lesions in patients with mild cognitive impairment due and not due to Alzheimer's disease

TL;DR

This study finds that brain wave patterns in patients with mild cognitive impairment are not worsened by white matter damage, regardless of whether the impairment is due to Alzheimer's disease.

Contribution

The study shows that white matter lesions do not affect resting-state alpha brain rhythms in mild cognitive impairment patients.

Findings

Posterior alpha brain activity was significantly reduced in MCI groups compared to healthy controls.

Increased white matter lesions were linked to worse executive function in non-Alzheimer's MCI patients.

Neurophysiological mechanisms regulating brain oscillations appear unaffected by white matter damage in MCI.

Abstract

Patients with mild cognitive impairment (MCI) typically show abnormal high delta (<4 Hz) and low alpha (8–12 Hz) rhythms measured from resting‐state eyes‐closed electroencephalographic (rsEEG) source activities as well as white matter lesions (WMLs) measured from magnetic resonance imaging (MRI). Here we tested the hypothesis that rsEEG rhythms may not deteriorate with the increase of WLMs in patients with MCI due and not due to Alzheimer's disease (ADMCI and noADMCI).

An international database provided demographic, clinical, and rsEEG datasets for cognitively unimpaired older (Healthy; N = 30), ADMCI (N = 64), and noADMCI (N = 36) participants. The rsEEG rhythms spanned individual delta, theta, and alpha frequency bands. The eLORETA freeware estimated cortical rsEEG sources. The international database also provided MRI datasets for the ADMCI and noADMCI participants. T2 and Fluid Attenuated Inversion Recovery (FLAIR) images estimated the WMLs.

The posterior rsEEG alpha source activities were lower in the groups of the ADMCI with a less increase of WMLs (ADMCI‐WML‐), ADMCI with a high increase of WMLs (ADMCI‐WML+), and noADMCI with a very high increase of WMLs (noADMCI‐WL++) compared to the Healthy group (p < 0.001; Figure 1). This effect was dramatic in the ADMCI‐WML‐ group, marked in the ADMCI‐WML+ group, and moderate in the noADMCI‐WML++. Furthermore, a positive association between the increase of WMLs and the worsening of executive function test scores (i.e., Trail making test part B‐A) was observed in the noADMCI group (t = 3.25, p < 0.005; Figure 2).

These results suggest that neurophysiological brain neural oscillatory synchronization mechanisms regulating cortical arousal and vigilance through alpha rsEEG rhythms are not affected by white matter tissue damage in MCI patients.

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