MEG Beamformer-Based Reconstructions of Functional Networks in Mild Cognitive Impairment
Maria E López1,2, Marjolein M A Engels3, Elisabeth C W van Straaten4,5
1Laboratory of Neuropsychology, Universitat de les Illes BalearsPalma de Mallorca, Spain.
Abstract:
Subjects with mild cognitive impairment (MCI) have an increased risk of developing Alzheimer's disease (AD), and their functional brain networks are presumably already altered. To test this hypothesis, we compared magnetoencephalography (MEG) eyes-closed resting-state recordings from 29 MCI subjects and 29 healthy elderly subjects in the present exploratory study. Functional connectivity in different frequency bands was assessed with the phase lag index (PLI) in source space. Normalized weighted clustering coefficient (normalized Cw) and path length (normalized Lw), as well as network measures derived from the minimum spanning tree [MST; i.e., betweenness centrality (BC) and node degree], were calculated. First, we found altered PLI values in the lower and upper alpha bands in MCI patients compared to controls. Thereafter, we explored network differences in these frequency bands. Normalized Cw and Lw did not differ between the groups, whereas BC and node degree of the MST differed, although these differences did not survive correction for multiple testing using the False Discovery Rate (FDR). As an exploratory study, we may conclude that: (1) the increases and decreases observed in PLI values in lower and upper alpha bands in MCI patients may be interpreted as a dual pattern of disconnection and aberrant functioning; (2) network measures are in line with connectivity findings, indicating a lower efficiency of the brain networks in MCI patients; (3) the MST centrality measures are more sensitive to detect subtle differences in the functional brain networks in MCI than traditional graph theoretical metrics.
Insights
Mild cognitive impairment (MCI) patients show altered brain network connectivity, particularly in alpha frequency bands, suggesting potential early signs of Alzheimer's disease (AD) progression. These changes indicate reduced brain network efficiency in individuals with MCI.
Area of Science:
- Neuroscience
- Medical Imaging
- Cognitive Science
Background:
- Mild cognitive impairment (MCI) is a known risk factor for Alzheimer's disease (AD).
- Functional brain networks are presumed to be altered in individuals with MCI.
Purpose of the Study:
- To investigate differences in functional brain network connectivity between MCI patients and healthy elderly controls.
- To explore alterations in specific frequency bands and network metrics.
Main Methods:
- Magnetoencephalography (MEG) resting-state recordings were used for 29 MCI subjects and 29 healthy controls.
- Functional connectivity was assessed using the phase lag index (PLI) in source space.
- Network measures including clustering coefficient, path length, and minimum spanning tree (MST) metrics (betweenness centrality, node degree) were calculated.
Main Results:
- Altered PLI values were observed in the lower and upper alpha bands in MCI patients compared to controls.
- While MST centrality measures (BC, node degree) differed between groups, these did not survive FDR correction.
- Network measures indicated potentially lower brain network efficiency in MCI patients.
Conclusions:
- Observed PLI changes in MCI patients suggest a dual pattern of disconnection and aberrant functioning in alpha bands.
- MST centrality measures show promise in detecting subtle functional brain network differences in MCI.
- Findings suggest reduced brain network efficiency in MCI, potentially preceding AD development.
