Large-Scale Network Connectivity and Cognitive Function Changes After Exercise Training in Older Adults with Intact Cognition and Mild Cognitive Impairment

Abstract

Background: Despite growing evidence regarding the association between exercise training (ET) and functional brain network connectivity, little is known about the effects of ET on large-scale within- and between-network functional connectivity (FC) of core brain networks.

Objective: We investigated the effects of ET on within- and between-network functional connectivity of the default mode network (DMN), frontoparietal network (FPN), and salience network (SAL) in older adults with intact cognition (CN) and older adults diagnosed with mild cognitive impairment (MCI). The association between ET-induced changes in FC and cognitive performance was examined.

Methods: 33 older adults (78.0±7.0 years; 16 MCI and 17 CN) participated in this study. Before and after a 12-week walking ET intervention, participants underwent a graded exercise test, Controlled Oral Word Association Test (COWAT), Rey Auditory Verbal Learning Test (RAVLT), a narrative memory test (logical memory; LM), and a resting-state fMRI scan. We examined the within (_W) and between (_B) network connectivity of the DMN, FPN, and SAL. We used linear regression to examine associations between ET-related changes in network connectivity and cognitive function.

Results: There were significant improvements in cardiorespiratory fitness, COWAT, RAVLT, and LM after ET across participants. Significant increases in DMN_W and SAL_W, and DMN-FPN_B, DMN-SAL_B, and FPN-SAL_B were observed after ET. Greater SAL_W and FPN-SAL_B were associated with enhanced LM immediate recall performance after ET in both groups.

Conclusion: Increased within- and between-network connectivity following ET may subserve improvements in memory performance in older individuals with intact cognition and with MCI due to Alzheimer's disease.

Keywords: Alzheimer’s disease; cognitive function; exercise training; functional connectivity; mild cognitive impairment; neural network; older adults; physical activity.

Fig. 1

Location of the nodes for each network defined by Power (2011) atlas [44]. Red: DMN (59 nodes); Yellow: FPN (25 nodes); and Black: SAL (18 nodes). Detailed coordinates for each node are presented in Supplementary Table 1.

Fig. 2

Group-averaged (CN and MCI) adjacency matrix representing functional connectivity of DMN, FPN, and SAL defined using Power (2011) atlas [44]. A) Before exercise training. B) After exercise training. C) After minus Before exercise training.

Fig. 3

A) Positive association of change in the salience network within-network connectivity and changes in logical memory immediate recall performance across participants (both MCI and CN). B) Positive associations of FPN-SAL between-network connectivity and logical memory immediate recall performance across participants (both MCI and CN). Dotted curves indicate 95% confidence interval around the mean.