Structural and functional connectivity in healthy aging: Associations for cognition and motor behavior

Abstract

Age-related behavioral declines may be the result of deterioration of white matter tracts, affecting brain structural (SC) and functional connectivity (FC) during resting state. To date, it is not clear if the combination of SC and FC data could better predict cognitive/motor performance than each measure separately. We probed these relationships in the cingulum bundle, a major white matter pathway of the default mode network. We aimed to attain deeper knowledge about: (a) the relationship between age and the cingulum's SC and FC strength, (b) the association between SC and FC, and particularly (c) how the cingulum's SC and FC are related to cognitive/motor performance separately and combined. We examined these associations in a healthy and well-educated sample of 165 older participants (aged 64-85). SC and FC were acquired using probabilistic tractography to derive measures to capture white matter integrity within the cingulum bundle (fractional anisotropy, mean, axial and radial diffusivity) and a seed-based resting-state functional MRI correlation approach, respectively. Participants performed cognitive tests measuring processing speed, memory and executive functions, and motor tests measuring motor speed and grip force. Our data revealed that only SC but not resting state FC was significantly associated with age. Further, the cingulum's SC and FC showed no relation. Different relationships between cognitive/motor performance and SC/FC separately were found, but no additive effect of the combined analysis of cingulum's SC and FC for predicting cognitive/motor performance was apparent.

Keywords: cingulum; cognitive aging; functional connectivity; multimodal imaging; tractography.

Figure 1

Mid‐sagittal image of the MNI152 template brain. Black indicates the posterior cingulate cortex and white the anterior region of interest, plaid indicates the genu of corpus callosum and gray the medial prefrontal cortex region of interest. Crosshairs represent the center of gravity of the genu of the corpus callosum.

Figure 2

Steps to create the final cingulum tract. Heat colors in the cingulum tract represent higher probability. Threshold level is set on 5%. Yellow depicts the spherical ROI used for the posterior cingulate cortex, the pink color indicates the anterior ROI. [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com.]