Disconnection of alpha oscillations within default mode network associated with memory dysfunction in amnestic MCI.

ABSTRACT

OBJECTIVE: Episodic memory dysfunction and alterations of functional connectivity (FC) in default mode network (DMN) were found in patients with amnestic mild cognitive impairment (aMCI). However, previous studies were limited in probing certain oscillations within the DMN. This study employed measures of resting-state FC across various oscillations within the DMN to comprehensively examine the FC and its association with episodic memory performance in aMCI. METHODS: Twenty-six healthy controls (HC) and 30 patients with aMCI were recruited to perform resting-state magnetoencephalographic recordings. We compared the spectral powers and peak frequency values in each frequency band and FC within the DMN between these two groups. The associations of FC values with memory performance were also examined. RESULTS: No significant between-group differences in spectral powers and peak frequency values were observed in the regional nodes. Patients with aMCI exhibited diminished alpha-band FC as compared to HC. Furthermore, lower alpha-band FC between the medial temporal cortex - and the posterior cingulate cortex/precuneus was correlated with poorer memory performance. CONCLUSIONS: Aberrant DMN connectivity, particularly in the alpha frequency range, might be a neural correlate of episodic memory impairment. SIGNIFICANCE: Our results inform the potential development of brain stimulation in managing memory impairments in aMCI.