Fronto-parietal coupling of brain rhythms in mild cognitive impairment: A multicentric EEG study

Abstract

Electroencephalographic (EEG) data were recorded in 69 normal elderly (Nold), 88 mild cognitive impairment (MCI), and 109 mild Alzheimer's disease (AD) subjects at rest condition, to test whether the fronto-parietal coupling of EEG rhythms is in line with the hypothesis that MCI can be considered as a pre-clinical stage of the disease at group level. Functional coupling was estimated by synchronization likelihood of Laplacian-transformed EEG data at electrode pairs, which accounts for linear and non-linear components of that coupling. Cortical rhythms of interest were delta (2-4Hz), theta (4-8Hz), alpha 1 (8-10.5Hz), alpha 2 (10.5-13Hz), beta 1 (13-20Hz), beta 2 (20-30Hz), and gamma (30-40Hz). Compared to the Nold subjects, the AD patients presented a marked reduction of the synchronization likelihood (delta to gamma) at both fronto-parietal and inter-hemispherical (delta to beta 2) electrodes. As a main result, alpha 1 synchronization likelihood progressively decreased across Nold, MCI, and mild AD subjects at midline (Fz-Pz) and right (F4-P4) fronto-parietal electrodes. The same was true for the delta synchronization likelihood at right fronto-parietal electrodes (F4-P4). For these EEG bands, the synchronization likelihood correlated with global cognitive status as measured by the Mini Mental State Evaluation. The present results suggest that at group level, fronto-parietal coupling of the delta and alpha rhythms progressively becomes abnormal though MCI and mild AD. Future longitudinal research should evaluate whether the present EEG approach is able to predict the cognitive decline in individual MCI subjects.

Resting-State EEG Power and Aperiodic Activity in Individuals with Mild Cognitive Impairment and Cognitively Healthy Controls

“…In contrast to the controls, we did not observe any significant relationship between resting-state EEG activity and cognitive performance in the MCI group. These findings differ from previous studies that have reported relationships between resting-state EEG power and MMSE [ 15 , 46 , 47 ] and delayed memory recall [ 48 ]. However, these studies did not control for aperiodic activity, which may have influenced the observed associations.…”

Resting-State EEG Power and Aperiodic Activity in Individuals with Mild Cognitive Impairment and Cognitively Healthy Controls

“…In contrast to the controls, we did not observe any significant relationship between resting-state EEG activity and cognitive performance in the MCI group. These findings differ from previous studies that have reported relationships between resting-state EEG power and MMSE [ 15 , 46 , 47 ] and delayed memory recall [ 48 ]. However, these studies did not control for aperiodic activity, which may have influenced the observed associations.…”

Changes in the EEG amplitude as a biomarker for early detection of Alzheimer's disease

“…3 and Table II show that PZ channel (parietal lobe) has the minimum p-value, followed by FZ (frontal lobe), P4, CZ (central lobe), F8, and T6 (temporal lobe). This illustrates, the gradual slowing of brain wave activity due to AD, starts from the back of the brain (parietal lobe) towards the front (frontal lobe) and from right to the left side and this finding is consistent with the other studies [13][20] [21][22] [23]. In addition, occipital lobe is the last part of the brain that affected by AD.…”

EEG-Based Semantic Vigilance Level Classification Using Directed Connectivity Patterns and Graph Theory Analysis

“…The decrement in the connectivity network across these regions in all the frequency bands confirm the vigilance decrement. It has been shown previously that frontal-to-parietal direction of information flux within EEG functional coupling is an intrinsic feature of brain network connectivity [66]. Our finding is in line with previous functional connectivity studies which found when mental fatigue level increases, the functional coupling decreases, specifically over the parietal-to-frontal regions in the single frequency bands [36][37][38].…”

Resting-State EEG Power and Aperiodic Activity in Individuals with Mild Cognitive Impairment and Cognitively Healthy Controls

“…In contrast to the controls, we did not observe any significant relationship between resting-state EEG activity and cognitive performance in the MCI group. These findings differ from previous studies that have reported relationships between resting-state EEG power and MMSE [ 15 , 46 , 47 ] and delayed memory recall [ 48 ]. However, these studies did not control for aperiodic activity, which may have influenced the observed associations.…”

Changes in the EEG amplitude as a biomarker for early detection of Alzheimer's disease

“…3 and Table II show that PZ channel (parietal lobe) has the minimum p-value, followed by FZ (frontal lobe), P4, CZ (central lobe), F8, and T6 (temporal lobe). This illustrates, the gradual slowing of brain wave activity due to AD, starts from the back of the brain (parietal lobe) towards the front (frontal lobe) and from right to the left side and this finding is consistent with the other studies [13][20] [21][22] [23]. In addition, occipital lobe is the last part of the brain that affected by AD.…”

EEG-Based Semantic Vigilance Level Classification Using Directed Connectivity Patterns and Graph Theory Analysis

“…The decrement in the connectivity network across these regions in all the frequency bands confirm the vigilance decrement. It has been shown previously that frontal-to-parietal direction of information flux within EEG functional coupling is an intrinsic feature of brain network connectivity [66]. Our finding is in line with previous functional connectivity studies which found when mental fatigue level increases, the functional coupling decreases, specifically over the parietal-to-frontal regions in the single frequency bands [36][37][38].…”

Resting-State EEG Power and Aperiodic Activity in Individuals with Mild Cognitive Impairment and Cognitively Healthy Controls

“…In contrast to the controls, we did not observe any significant relationship between resting-state EEG activity and cognitive performance in the MCI group. These findings differ from previous studies that have reported relationships between resting-state EEG power and MMSE [ 15 , 46 , 47 ] and delayed memory recall [ 48 ]. However, these studies did not control for aperiodic activity, which may have influenced the observed associations.…”

Changes in the EEG amplitude as a biomarker for early detection of Alzheimer's disease

“…3 and Table II show that PZ channel (parietal lobe) has the minimum p-value, followed by FZ (frontal lobe), P4, CZ (central lobe), F8, and T6 (temporal lobe). This illustrates, the gradual slowing of brain wave activity due to AD, starts from the back of the brain (parietal lobe) towards the front (frontal lobe) and from right to the left side and this finding is consistent with the other studies [13][20] [21][22] [23]. In addition, occipital lobe is the last part of the brain that affected by AD.…”

EEG-Based Semantic Vigilance Level Classification Using Directed Connectivity Patterns and Graph Theory Analysis

“…The decrement in the connectivity network across these regions in all the frequency bands confirm the vigilance decrement. It has been shown previously that frontal-to-parietal direction of information flux within EEG functional coupling is an intrinsic feature of brain network connectivity [66]. Our finding is in line with previous functional connectivity studies which found when mental fatigue level increases, the functional coupling decreases, specifically over the parietal-to-frontal regions in the single frequency bands [36][37][38].…”