Mapping distributed sources of cortical rhythms in mild Alzheimer's disease. A multicentric EEG study

Abstract

The study aimed at mapping (i) the distributed electroencephalographic (EEG) sources specific for mild Alzheimer's disease (AD) compared to vascular dementia (VaD) or normal elderly people (Nold) and (ii) the distributed EEG sources sensitive to the mild AD at different stages of severity. Resting EEG (10-20 electrode montage) was recorded from 48 mild AD, 20 VaD, and 38 Nold subjects. Both AD and VaD patients had 24-17 of mini mental state examination (MMSE). EEG rhythms were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). Cortical EEG sources were modeled by low resolution brain electromagnetic tomography (LORETA). Regarding issue i, there was a decline of central, parietal, temporal, and limbic alpha 1 (low alpha) sources specific for mild AD group with respect to Nold and VaD groups. Furthermore, occipital alpha 1 sources showed a strong decline in mild AD compared to VaD group. Finally, distributed theta sources were largely abnormal in VaD but not in mild AD group. Regarding issue ii, there was a lower power of occipital alpha 1 sources in mild AD subgroup having more severe disease. Compared to previous field studies, this was the first investigation that illustrated the power spectrum profiles at the level of cortical (macroregions) EEG sources in mild AD patients having different severity of the disease with respect to VaD and normal subjects. Future studies should evaluate the clinical usefulness of this approach in early differential diagnosis, disease staging, and therapy monitoring.

MEG spectral analysis in subtypes of mild cognitive impairment

“…Nonetheless, overall our findings seem to confirm the hypothesis of a spectral pattern more proximate to the typical AD profile, mainly in a-md-MCIs. 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).…”

Nonlinear analysis of electroencephalogram and magnetoencephalogram recordings in patients with Alzheimer's disease

“…These analyses seem to discriminate AD patients from control subjects through an increased EEG/MEG activity in lower frequency bands associated with this dementia (Babiloni et al 2004;Fernández et al 2006). To be more precise, a decreased mean frequency, an increase in delta and theta power, and a decrease in alpha and beta power are observed in AD patients compared with that of normal elderly subjects (Babiloni et al 2004;Jeong 2004;Fernández et al 2006;Rossini et al 2007). The earliest changes are an increase in theta activity and a decrease in beta activity, which are followed by a decrease in alpha activity, and then an increase in delta activity (Jeong 2004).…”

Donepezil effects on sources of cortical rhythms in mild Alzheimer's disease: Responders vs. Non-Responders

“…In humans, EEG rhythms differ in AD patients compared to normal controls and/or vascular dementia subjects. AD patients were characterized by higher delta (0 -3 Hz), higher theta (4 -7 Hz), lower posterior alpha (8 -12 Hz), slowing in alpha peak frequency, and lower beta (14 -30 Hz) and gamma (around 40 Hz) (Dierks et al, 1993Huang et al, 2000;Wolf et al, 2003;Babiloni et al, 2004;Moretti et al, 2004;Adeli and GhoshDastidar, 2005). The abnormality of EEG rhythms in dementia has been associated with altered rCBF/metabolism and cognitive function (Szelies et al, 1992;Julin et al, 1995;Passero et al, 1995;Sloan et al, 1995;Rodriguez et al, 1999aRodriguez et al, , 1999b.…”