Stability of clinical condition in mild cognitive impairment is related to cortical sources of alpha rhythms: An electroencephalographic study

Abstract

Previous evidence has shown that resting eyes-closed cortical alpha rhythms are higher in amplitude in mild cognitive impairment (MCI) than Alzheimer's disease (AD) subjects (Babiloni et al. [2006a]: Human Brain Mapp 27:162-172; [2006b]: Clin Neurophysiol 117:252-268; [2006c]: Neuroimage 29:948-964; [2006d]: Ann Neurol 59:323-334; [2006e]: Clin Neurophysiol 117:1113-1129; [2006f]: Neuroimage 31:1650-1665). This study tested the hypothesis that, in amnesic MCI subjects, high amplitude of baseline cortical alpha rhythms is related to long-term stability of global cognition on clinical follow-up. Resting electroencephalographic (EEG) data were recorded in 100 amnesic MCI subjects during eyes-closed condition. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha1 (8-10.5 Hz), alpha2 (10.5-13 Hz), beta1 (13-20 Hz), and beta2 (20-30 Hz). Cortical EEG sources were estimated by low-resolution brain electromagnetic tomography (LORETA). Global cognition was indexed by mini mental state evaluation (MMSE) score at the time of EEG recordings (baseline) and about after 1 year. Based on the MMSE percentage difference between baseline and 1-year follow-up (MMSEvar), the MCI subjects were retrospectively divided into three arbitrary groups: DECREASED (MMSEvar ≤ -4%; N = 43), STABLE (MMSEvar ≈ 0; N = 27), and INCREASED (MMSEvar ≥ +4%; N = 30). Subjects' age, education, individual alpha frequency, gender, and MMSE scores were used as covariates for statistical analysis. Baseline posterior cortical sources of alpha 1 rhythms were higher in amplitude in the STABLE than in the DECREASED and INCREASED groups. These results suggest that preserved resting cortical neural synchronization at alpha frequency is related to a long-term (1 year) stable cognitive function in MCI subjects. Future studies should use serial MMSE measurements to confirm and refine the present results.

Rate of Conversion from Prodromal Alzheimer's Disease to Alzheimer's Dementia: A Systematic Review of the Literature

“…Fifty-eight relevant publications met the eligibility criteria; however, 22 were determined to have reported on related study samples and were not included in the review. A total of 36 citations reporting data from 32 independent patient populations were identified for inclusion in this review [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47]. The data for two time intervals were obtained from separate publications on related populations from 4 studies that were conducted in France [35,39], Italy [37,42], the Netherlands [34,43], and the USA [22,33].…”

The Default Mode Network is functionally and structurally disrupted in amnestic mild cognitive impairment — A bimodal MEG–DTI study

“…Alpha band alterations are in fact well-known in MCI and they have been shown to relate for instance to the stability of the clinical condition (Babiloni et al, 2011) or amygdalo–hippocampal atrophy (Moretti et al, 2009). Additionally, the alpha band seems to be the most relevant frequency band in the DMN, even in healthy subjects.…”

Healthy and Pathological Brain Aging: From the Perspective of Oscillations, Functional Connectivity, and Signal Complexity

“…Based on these results, it has been proposed that, cognitive and functional status being equal, patients with AD who are EEG-positive for this marker may show a neurophysiological susceptibility, which could be used to improve the diagnosis in clinical studies or to assess the efficacy of pharmacological interventions [18]. Findings in other EEG studies on mild cognitive impairment (MCI) indicate that alpha rhythm can also discriminate patients with a stable cognitive state from those with unstable global cognition [19]. Furthermore, alpha reactivity to eye-opening shows a progressive impairment from healthy elderly to mild AD that correlates with cognitive decline [20].…”