Functional Hypo-connectivity in Mild Cognitive Impairment during Alpha Modulation Task: An MEG Study

Most existing Mild cognitive impairment (MCI) research explored brain activity during resting state (RS) with either eyes-open (EO) or eyes-closed (EC), memory or visuospatial task but to the best of authors’ knowledge, no study has been reported on alteration in functional brain connectivity (FC) during alpha-modulation task where frequent switching of default mode network and focus engaging task positive network (TPN) takes place. In this work, FC has been studied between 16 healthy and 5 MCI patients in source-level magnetoencephalography data, recorded from participants sitting still with alternating EC and EO conditions for 12~18 seconds for 8 minutes. The data was band-pass filtered (0.5-100 Hz) and artifact corrected before source transformation using linearly constraint minimum variance beamformer to reconstruct 122 source-level time-series. Phase synchrony was measured to construct FC for alpha and beta rhythms as they are associated with awake resting state and focus respectively. Significant FC alterations between two groups were identified by Wilcoxon’s signed-rank test with 5% threshold. Alpha activity shows connectivity decline (hypo-connectivity) in anterior cingulate cortex (ACC) and Wernicke’s area for MCI compared to healthy, while beta band hypo-connectivity is observed in occipital, cerebral cortex, ACC, frontal and temporal areas (Fig.1). For both cases, hyper-connectivity has been observed in central, parietal and temporal regions. TPN thus unfolds important FC alterations in MCI normally associated with disease progression. As previous studies confirmed that MCI patients struggle to focus and have difficulties in word comprehension in conversation, identified network alterations can serve as potential neuromarkers for MCI diagnosis.