Abstract
Both episodic memory and executive function are impaired in amnestic mild cognitive impairment (aMCI) subjects, but it is unclear if these impairments are independent or interactive. The present study aimed to explore the relationship between episodic memory deficits and executive function deficits, and the underlying functional mechanisms in aMCI subjects. Thirty-one aMCI subjects and 27 healthy subjects underwent neuropsychological tests and multimodal magnetic resonance imaging (MRI) scans. Hippocampal networks and medial prefrontal cortex (MPFC) networks were identified based on resting-sate functional MRI (fMRI) data. AMCI subjects displayed lower episodic memory scores and executive function scores than control subjects, and the episodic memory scores were positively correlated with the executive function scores in aMCI subjects. Brain network analyses showed an interaction between the hippocampal networks and the MPFC networks, and the interaction was significantly associated with the episodic memory scores and the executive function scores. Notably, aMCI subjects displayed higher functional connectivity (FC) of the right hippocampal network with the right prefrontal cortex than did control subjects, but this difference disappeared when controlling for the MPFC networks. Furthermore, the effects of the MPFC networks on the hippocampal networks were significantly associated with the episodic memory scores in aMCI subjects. The present findings suggested that the episodic memory deficits in aMCI subjects could be partially underpinned by the modulation of the MPFC networks on the hippocampal networks.
Highlights
Alzheimer’s disease (AD) is usually characterized by episodic memory deficits and impairment in other cognitive domains, including executive function, language, and visuospatial function
Normed relative to the control group, the auditory-verbal learning test (AVLT)-DR performance of the amnestic mild cognitive impairment (aMCI) group was more impaired than the auditory verbal learning test-immediate recalls (AVLT-IR) performance (Supplementary Figure 1), suggesting that delayed recall was more impaired than encoding in the aMCI group
The episodic memory scores were significantly positively correlated with the executive function scores in the aMCI group (r = 0.530, P = 0.008), not in the control group (r = 0.236, P = 0.266) (Figure 1)
Summary
Alzheimer’s disease (AD) is usually characterized by episodic memory deficits and impairment in other cognitive domains, including executive function, language, and visuospatial function. The hippocampus plays a key role in episodic memory processing, and the medial prefrontal cortex (MPFC) serves as a central component of systems involved in executive processing (Leh et al, 2010; Brown, 2011). Both the hippocampus and the prefrontal lobe are vulnerable to damages induced by aging or aging-related disease (Moscovitch and Winocur, 1995; West, 1996; Wu et al, 2008). It is largely unclear if episodic memory loss and executive decline are independent or interactive in aMCI patients
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