Cerebrovascular Disease and Hippocampal Atrophy Are Differently Linked to Functional Coupling of Brain Areas: An EEG Coherence Study in MCI Subjects

Abstract

The working hypothesis of paper is that the functional coupling of brain areas is combined with different neuroradiological substrates and has different clinical manifestations. 31 normal old subjects and 85 subjects with mild cognitive impairment (MCI) underwent EEG recordings and magnetic resonance imaging (MRI). Intrahemispheric and interhemispheric linear EEG coherences were computed. At first, all normal old and MCI subjects were compared. Subsequently, three subgroups of MCI were obtained based on neuroradiological substrate (subcortical cerebrovascular damage, MCI-CVD; cholinergic pathways vascular damage MCI-CHOL; and hippocampal atrophy, MCI-HIPP) and compared with a normal old sample matched for age, education and Mini-Mental State Examination score. The group of MCI subjects compared to normal old subjects shows: 1) decrease of intrahemispheric coherence in fronto-parietal regions (both right and left hemisphere); 2) increase of interhemispheric coherence on frontal regions in delta frequency; and 3) increase of interhemispheric coherence on temporal regions (from delta to alpha3 frequency bands). In the MCI subgroups, hippocampal atrophy is linked to an increase of interhemispheric coherence seen on frontal and temporal regions whereas subcortical CVD is linked to the largest decrease of coherence in fronto-parietal regions. MCI-CVD patients performed worst on Trail Making Test battery whereas MCI-HIPP patients were impaired on Rey word list delayed recall and Rey figure recall.

Synchronization during an internally directed cognitive state in healthy aging and mild cognitive impairment: a MEG study

“…Finally, MCIs showed a higher synchronization in the gamma band between right anterior and central areas, which was related to a poorer performance in attention, memory, and executive function, while in the control group, this increase was localized in more posterior regions and was directly correlated with a greater hippocampal volume and higher scores in MMSE, Immediate and Delayed Recall, and Semantic Fluency. Most of these findings, and especially the decrease in synchronization in alpha and beta bands, are in agreement with those found in MCI and AD studies (Berendse et al 2000;Jelic et al 2000;Koenig et al 2005;Stam et al 2003;Moretti et al 2008;Gómez et al 2009), suggesting that MCI could be considered as the beginning of the "disconnection syndrome" (Delbeuck et al 2003). …”

“…For example, Moretti et al (2008) reported a decline in intrahemispheric fronto-parietal coherence and an increase in temporal interhemispheric coherence in the MCI group when compared to elderly controls and also a reduced beta band functional connectivity. Gómez et al (2009) found a decreased synchronization essentially in the beta band in MCI subjects.…”

Dynamic information flow analysis in Vascular Dementia patients during the performance of a visual oddball task

“…Based on such consideration, the DTF connectivity were integrated into 5 frequency bands, i.e. ı (0.5-3.5 Hz), Â (4-7 Hz), ˛1 (8-10 Hz), ˛2 (11)(12)(13) and (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and then statistic tests were performed again. Significant directional connectivity was visualized over the scalp surface using the eConnectome software package [22].…”

“…In a study based on coherence analysis with combined EEG and MRI, it was found that MCI patients with subcortical cerebrovascular damage showed a largest decrease in the coherence of fronto-parietal regions in the three MCI subgroups [30]. Another study of resting EEG found that there was a significant correlation between parietal-to-frontal information flow strength and subcortical white matter vascular lesions scores [31].…”

Electroencephalography reveals lower regional blood perfusion and atrophy of the temporoparietal network associated with memory deficits and hippocampal volume reduction in mild cognitive impairment due to Alzheimer’s disease

“…In the conceptual framework concerning integration of biomarkers for an early and highly predictive diagnosis, the electroencephalogram (EEG) could be a reliable tool 5–11. Indeed, it is widely accepted that EEG rhythms reflect underlying brain network activity 12–16. As a consequence, changes in EEG rhythms could be an early sign of AD.…”