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. 2017;57(3):845-856.
doi: 10.3233/JAD-161151.

Exercise Training and Functional Connectivity Changes in Mild Cognitive Impairment and Healthy Elders

Theresa J Chirles  1 , Katherine Reiter  2 , Lauren R Weiss  1 , Alfonso J Alfini  1 , Kristy A Nielson  2   3 , J Carson Smith  1
Affiliations

Exercise Training and Functional Connectivity Changes in Mild Cognitive Impairment and Healthy Elders

Theresa J Chirles et al. J Alzheimers Dis. 2017.

Abstract

Background: Effective interventions are needed to improve brain function in mild cognitive impairment (MCI), an early stage of Alzheimer's disease (AD). The posterior cingulate cortex (PCC)/precuneus is a hub of the default mode network (DMN) and is preferentially vulnerable to disruption of functional connectivity in MCI and AD.

Objective: We investigated whether 12 weeks of aerobic exercise could enhance functional connectivity of the PCC/precuneus in MCI and healthy elders.

Methods: Sixteen MCI and 16 healthy elders (age range = 60-88) engaged in a supervised 12-week walking exercise intervention. Functional MRI was acquired at rest; the PCC/precuneus was used as a seed for correlated brain activity maps.

Results: A linear mixed effects model revealed a significant interaction in the right parietal lobe: the MCI group showed increased connectivity while the healthy elders showed decreased connectivity. In addition, both groups showed increased connectivity with the left postcentral gyrus. Comparing pre to post intervention changes within each group, the MCI group showed increased connectivity in 10 regions spanning frontal, parietal, temporal and insular lobes, and the cerebellum. Healthy elders did not demonstrate any significant connectivity changes.

Conclusion: The observed results show increased functional connectivity of the PCC/precuneus in individuals with MCI after 12 weeks of moderate intensity walking exercise training. The protective effects of exercise training on cognition may be realized through the enhancement of neural recruitment mechanisms, which may possibly increase cognitive reserve. Whether these effects of exercise training may delay further cognitive decline in patients diagnosed with MCI remains to be demonstrated.

Keywords: Aging; Alzheimer’s disease; cognitive disorders; connectivity; default mode network; exercise intervention; neural plasticity; posterior cingulate; precuneus; resting state functional MRI.

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Figures

Figure 1.
Figure 1.
Statistically significant (family-wise error corrected, p < .05) Group by Time interactions and main effects of Time for functional connectivity of the PCC/precuneus in response to a 12-week walking exercise intervention in older adults diagnosed with mild cognitive impairment (MCI; n = 16) and healthy elders (HE; n = 16). Age and education were entered as covariates. The mean correlation coefficients, MNI coordinates, and cluster size for each region are shown in Table 2. Panel A: A significant Group by Time interaction was found in the right inferior parietal lobule (IPL), where functional connectivity with the PCC/precuneus increased after exercise training in the MCI group and decreased in the HE group. Panel B: Functional connectivity significantly increased between the PCC/precuneus and the postcentral gyrus after exercise training in both the MCI and HE groups.
Figure 2.
Figure 2.
Resting state functional connectivity changes with the PCC/precuneus seed region in response to a 12-week walking exercise intervention in older adults diagnosed with mild cognitive impairment (MCI; n = 16). Age and education were entered as covariates. All 10 highlighted brain regions indicate increased functional connectivity with the PCC/precuneus from before to after exercise training (family-wise error corrected, p < .05). The MNI coordinates and cluster sizes for each region are shown in Table 3.
See this image and copyright information in PMC

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