Event-related synchronization of alpha activity in early Alzheimer's disease and mild cognitive impairment: An MEG study combining beamformer and group … (original) (raw)
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Journal of Alzheimers Disease, 2010
Cortical sources of resting eyes-closed alpha rhythms are typically abnormal in mild cognitive impairment (MCI) and Alzheimer's disease (AD) subjects. Here we tested the hypothesis of a progressive impairment of cortical alpha reactivity to eyeopening across amnesic MCI and mild AD subjects, reflecting another aspect of the impairment of cortical neural synchronization. Resting electroencephalography (EEG) data were recorded in 36 normal elderly subjects (Nold), 91 amnesic MCI, and 31 mild AD subjects during eyes-closed and -open conditions. EEG sources were estimated by LORETA software. In the eye-closed condition, posterior alpha 1 (8-10.5 Hz) sources were lower in MCI and AD than Nold subjects. The opposite was true for occipital delta sources (2-4 Hz). Reactivity to the eyes-open condition showed posterior alpha 1 and alpha 2 (10.5-13 Hz) sources was high in the Nold, intermediate in the MCI, and low in the AD subjects. Furthermore, occipital alpha 1 reactivity across MCI and AD subjects was correlated to the cognitive impairment as revealed by Mini-Mental State Examination score. In conclusion, at least at group level, the continuum across amnesic MCI and mild AD status is related to an impaired reactivity of cortical neuronal synchronization to eyes opening at alpha rhythms. memory complaints and cognitive impairment on neuropsychological testing not yet fulfilling the clinical picture of dementia . Amnesic MCI is regarded as a precursor of Alzheimer's disease (AD) [4-6] since recent studies have shown a high rate of progression to AD [3,. In cognitively intact elderly subjects, the incidence of AD ranges from 0.17 to 3.86% , while in amnesic MCI subjects it ranges from 6 to 25% . However, the "transition" hypothesis is chal-
Psychogeriatrics, 2010
Background: Induced-oscillatory activity is considered a key factor for understanding functional processes in the brain. Magnetoencephalography (MEG) can measure oscillatory activity non-invasively with higher spatial resolution than electroencephalography (EEG). However, MEG has rarely been used to explore functional abnormalities that may represent state markers in patients with Alzheimer's disease (AD). Methods: Thirteen patients with early AD and 14 age-matched normal controls participated in the present study. Magnetoencephalography activity was acquired during eyes-open and eyes-closed states. Alpha event-related synchronization (ERS) after eye closing was calculated and its cortical sources superimposed on each individual's magnetic resonance imaging (MRI) scan. The resulting functional image was converted into a Talairachtransformed anatomical brain image and group comparisons were made. We also assessed correlations between cortical ERS sources showing significant between-group differences in alpha activity and external clinical parameters, especially measures of cognitive function. Results: The averaged alpha ERS after eye closing appeared dominantly in posterior brain regions in both patients with AD and healthy controls. However, there was a significant increase in alpha ERS in frontal regions, maximal over the prefrontal cortex, in patients with AD relative to controls, indicating a frontal shift of the posterior dominant MEG alpha rhythm in AD patients. This frontal ERS source in the alpha band was negatively correlated with Mini-Mental State Examination scores in the AD patient group. Conclusions: The findings indicate that a frontal shift of alpha ERS elicited by an eyes-open/eyes-closed paradigm may be an early brain electromagnetic change in patients with AD, probably representing a physiological state marker of the disease. Furthermore, the results confirm that the beamformer with group comparison analysis is a useful tool with which to explore functional processes in the brain, as indicated by oscillatory activity changes.
Cortical alpha rhythms in mild Alzheimer's disease. A multicentric EEG study
International Congress Series, 2004
The study aimed at mapping (i) the distributed alpha (8 -13 Hz) electroencephalography 22 (EEG) sources specific for mild Alzheimer's disease (AD) compared with vascular dementia (VaD) 23 in normal, elderly people (Nold) and (ii) the distributed alpha EEG sources sensitive to mild AD at 24 different stages of severity. Resting EEG (10 -20 electrode montage) was recorded from 48 mild AD, 25 20 VaD and 38 Nold subjects. Both AD and VaD patients had 24 -17 on their mini mental state 26 examinations (MMSE). Alpha bands were subdivided in alpha 1 (8 -10.5 Hz) and alpha 2 (10.5 -13 27 Hz) subbands. Cortical alpha EEG sources were modeled by ''low resolution brain electromagnetic 28 tomography'' (LORETA). Regarding issue (i), there was a decline of central, parietal, temporal and 29 limbic alpha 1 sources specific to the mild AD group with respect to Nold and VaD groups. On the 30 other hand, occipital alpha 1 sources showed a strong decline in mild AD compared with the VaD 31 group. However, this finding was ''unspecific'' because a certain decline of these sources was also 32 recognized in VaD compared with Nold. Regarding issue (ii), there was a lower power of occipital 33 alpha 1 sources in the mild AD more severely diseased subgroup. On the whole, these findings stress 0531-5131/ D 2004 Published by Elsevier B.V.
Human Brain Mapping, 2011
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. ]: 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 followup. 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 À4%; N ¼ 43), STABLE (MMSEvar % 0; N ¼ 27), and INCREASED (MMSEvar ! þ4%; N ¼ 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) sta-Published online in Wiley Online Library (wileyonlinelibrary. com).
EEG epochs with less alpha rhythm improve discrimination of mild Alzheimer's
Computer methods and programs in biomedicine, 2017
Eyes-closed-awake electroencephalogram (EEG) is a useful tool in the diagnosis of Alzheimer's. However, there is eyes-closed-awake EEG with dominant or rare alpha rhythm. In this paper, we show that random selection of EEG epochs disregarding the alpha rhythm will lead to bias concerning EEG-based Alzheimer's Disease diagnosis. We compared EEG epochs with more than 30% and with less than 30% alpha rhythm of mild Alzheimer's Disease patients and healthy elderly. We classified epochs as dominant alpha scenario and rare alpha scenario according to alpha rhythm (8-13 Hz) percentage in O1, O2 and Oz channels. Accordingly, we divided the probands into four groups: 17 dominant alpha scenario controls, 15 mild Alzheimer's patients with dominant alpha scenario epochs, 12 rare alpha scenario healthy elderly and 15 mild Alzheimer's Disease patients with rare alpha scenario epochs. We looked for group differences using one-way ANOVA tests followed by post-hoc multiple compar...
International Journal of Geriatric Psychiatry, 2008
Objective The study objective is to evaluate the use of qEEG data for the cross-sectional differentiation of mild cognitive impairment (MCI) from mild Alzheimer's disease (AD) and in the longitudinal prediction of cognitive decline in MCI. Methods Eighty-eight subjects with MCI and 42 subjects with mild probable AD were enrolled. Baseline EEGs were recorded using a 32-channel system with electrode positioning according to the international 10-20 system. Digitalized EEG data were further studied by quantitative spectral analysis. Study subjects were followed up for 1 year and reassessed psychometrically. An increase of the total ADAS-cog score of ! 4 points was regarded as a significant cognitive decline. Using this cut-off, MCI subjects were sub-grouped into stable MCI (s-MCI) and progressing MCI (p-MCI).