EEG alpha band functional connectivity and network structure mark hub overload in Mild Cognitive Impairment during memory maintenance

Fodor, Z.; Horváth, A.; Hidasi, Z.; Gouw, A.; Stam, C.; Csukly, G. · 2022 · DOAJ

DOI: 10.1192/j.eurpsy.2022.845

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Summary

This study investigates the neural mechanisms underlying cognitive decline in the early stages of Mild Cognitive Impairment (MCI) by examining EEG functional connectivity (FC) and network structure during visuospatial memory maintenance. While previous research has established decreased alpha-band FC and altered network topology in Alzheimer’s disease, the specific dynamics during the earliest stages of cognitive decline remain unclear. The authors aimed to determine whether differences in alpha-band FC and network organization between MCI patients and healthy elderly individuals with subjective memory complaints could mark hub overload and cognitive decline. The study employed a cross-sectional design involving 17 MCI patients and 20 healthy control participants. Data were collected using 128-channel EEG while participants performed a visuospatial memory task. Functional connectivity was measured using amplitude envelope correlation with leakage correction (AEC-c). Network analysis was conducted using the Minimum Spanning Tree approach to evaluate topological properties. This methodology allowed for the assessment of how increasing memory load affected neural connectivity and network integration in both groups. The results demonstrated distinct patterns of connectivity modulation between the two groups. In the control group, increasing memory load enhanced mean alpha-band FC. Conversely, the MCI group exhibited a significant decrease in FC (p<0.05) under the highest memory load conditions, following an initial increase. Furthermore, mean alpha AEC-c correlated significantly with the size and mean diffusivity of medial temporal lobe structures across the entire sample. Network analysis revealed that the MCI group possessed a rerouted network characterized by a more centralized topology and a more unequal traffic load distribution compared to controls. These findings indicate that alpha-band FC correlates with cognitive load-related modulation, medial temporal lobe atrophy, and the disruption of hippocampal fiber integrity in the earliest stages of cognitive decline. The more integrated network topology observed in the MCI group aligns with the “hub overload and failure” framework, suggesting that these structural changes may represent a compensatory mechanism. The study concludes that EEG alpha-band functional connectivity and network structure serve as markers for hub overload in MCI, providing insight into the neural underpinnings of early cognitive impairment.

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• mci dementia driving