Limits...
White matter microstructure contributes to age-related declines in task-induced deactivation of the default mode network.

Brown CA, Hakun JG, Zhu Z, Johnson NF, Gold BT - Front Aging Neurosci (2015)

Bottom Line: Older adults are known to show reductions in deactivation of the DMN compared to younger adults.Critically, mediation analyses indicated that age-related reductions in WM microstructure accounted for the relationship between age and DMN deactivation in the more difficult mixed condition.These findings suggest that age-related declines in anatomical connectivity between DMN regions contribute to functional dysregulation within the DMN in older adults.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington, KY, USA.

ABSTRACT
Task-induced deactivations within the brain's default mode network (DMN) are thought to reflect suppression of endogenous thought processes to support exogenous goal-directed task processes. Older adults are known to show reductions in deactivation of the DMN compared to younger adults. However, little is understood about the mechanisms contributing to functional dysregulation of the DMN in aging. Here, we explored the relationships between functional modulation of the DMN and age, task performance and white matter (WM) microstructure. Participants were 117 adults ranging from 25 to 83 years old who completed an fMRI task switching paradigm, including easy (single) and difficult (mixed) conditions, and underwent diffusion tensor imaging (DTI). The fMRI results revealed an age by condition interaction (β = -0.13, t = -3.16, p = 0.002) such that increasing age affected deactivation magnitude during the mixed condition (β = -0.29, t = -3.24 p = 0.002) but not the single condition (p = 0.58). Additionally, there was a WM by condition interaction (β = 0.10, t = 2.33, p = 0.02) such that decreasing WM microstructure affected deactivation magnitude during the mixed condition (β = 0.30, t = 3.42 p = 0.001) but not the single condition (p = 0.17). Critically, mediation analyses indicated that age-related reductions in WM microstructure accounted for the relationship between age and DMN deactivation in the more difficult mixed condition. These findings suggest that age-related declines in anatomical connectivity between DMN regions contribute to functional dysregulation within the DMN in older adults.

No MeSH data available.


Related in: MedlinePlus

Task-induced deactivation in the default mode network (DMN) and DMN white matter (WM) pathways. (A) Regions showing significant deactivation at FWE-corrected p < 0.05. (B) Statistical map of probabilistic tractography indicating the proportion of streamlines passing through each voxel. The scale indicates a minimum value of 0.001 (0.1%) of all attempted streamlines passing through a given voxel, while the maximum was set at 0.015 (1.5%) of all attempted streamlines passing through a given voxel. Coordinate below each image is the MNI coordinate for that slice. (C,D) WM pathways (blue) connecting DMN regions (red) after averaging the entire group and thresholding at 0.1% of all streamlines attempted passing through a voxel. The WM pathways shown in blue were used to extract fractional anisotropy (FA) in each participant. LOC, lateral occipital cortex; MTG, middle temporal gyrus; HC, hippocampus; PCC, posterior cingulate cortex; MPFC, medial prefrontal cortex.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4598480&req=5

Figure 1: Task-induced deactivation in the default mode network (DMN) and DMN white matter (WM) pathways. (A) Regions showing significant deactivation at FWE-corrected p < 0.05. (B) Statistical map of probabilistic tractography indicating the proportion of streamlines passing through each voxel. The scale indicates a minimum value of 0.001 (0.1%) of all attempted streamlines passing through a given voxel, while the maximum was set at 0.015 (1.5%) of all attempted streamlines passing through a given voxel. Coordinate below each image is the MNI coordinate for that slice. (C,D) WM pathways (blue) connecting DMN regions (red) after averaging the entire group and thresholding at 0.1% of all streamlines attempted passing through a voxel. The WM pathways shown in blue were used to extract fractional anisotropy (FA) in each participant. LOC, lateral occipital cortex; MTG, middle temporal gyrus; HC, hippocampus; PCC, posterior cingulate cortex; MPFC, medial prefrontal cortex.

Mentions: Results from the voxelwise contrast of the baseline fixation condition compared to the single task condition across participants revealed deactivation in the PCC, medial prefrontal cortex (MPFC), and in bilateral portions of lateral occipital cortex (LOC), HC, and middle temporal gyrus (MTG; Figure 1A). Coordinates of peak voxels within each cluster are listed in Table 2. A DMN mask was generated surrounding peak coordinates within each cluster (as described in Defining a Common DMN Network).


White matter microstructure contributes to age-related declines in task-induced deactivation of the default mode network.

Brown CA, Hakun JG, Zhu Z, Johnson NF, Gold BT - Front Aging Neurosci (2015)

Task-induced deactivation in the default mode network (DMN) and DMN white matter (WM) pathways. (A) Regions showing significant deactivation at FWE-corrected p < 0.05. (B) Statistical map of probabilistic tractography indicating the proportion of streamlines passing through each voxel. The scale indicates a minimum value of 0.001 (0.1%) of all attempted streamlines passing through a given voxel, while the maximum was set at 0.015 (1.5%) of all attempted streamlines passing through a given voxel. Coordinate below each image is the MNI coordinate for that slice. (C,D) WM pathways (blue) connecting DMN regions (red) after averaging the entire group and thresholding at 0.1% of all streamlines attempted passing through a voxel. The WM pathways shown in blue were used to extract fractional anisotropy (FA) in each participant. LOC, lateral occipital cortex; MTG, middle temporal gyrus; HC, hippocampus; PCC, posterior cingulate cortex; MPFC, medial prefrontal cortex.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4598480&req=5

Figure 1: Task-induced deactivation in the default mode network (DMN) and DMN white matter (WM) pathways. (A) Regions showing significant deactivation at FWE-corrected p < 0.05. (B) Statistical map of probabilistic tractography indicating the proportion of streamlines passing through each voxel. The scale indicates a minimum value of 0.001 (0.1%) of all attempted streamlines passing through a given voxel, while the maximum was set at 0.015 (1.5%) of all attempted streamlines passing through a given voxel. Coordinate below each image is the MNI coordinate for that slice. (C,D) WM pathways (blue) connecting DMN regions (red) after averaging the entire group and thresholding at 0.1% of all streamlines attempted passing through a voxel. The WM pathways shown in blue were used to extract fractional anisotropy (FA) in each participant. LOC, lateral occipital cortex; MTG, middle temporal gyrus; HC, hippocampus; PCC, posterior cingulate cortex; MPFC, medial prefrontal cortex.
Mentions: Results from the voxelwise contrast of the baseline fixation condition compared to the single task condition across participants revealed deactivation in the PCC, medial prefrontal cortex (MPFC), and in bilateral portions of lateral occipital cortex (LOC), HC, and middle temporal gyrus (MTG; Figure 1A). Coordinates of peak voxels within each cluster are listed in Table 2. A DMN mask was generated surrounding peak coordinates within each cluster (as described in Defining a Common DMN Network).

Bottom Line: Older adults are known to show reductions in deactivation of the DMN compared to younger adults.Critically, mediation analyses indicated that age-related reductions in WM microstructure accounted for the relationship between age and DMN deactivation in the more difficult mixed condition.These findings suggest that age-related declines in anatomical connectivity between DMN regions contribute to functional dysregulation within the DMN in older adults.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington, KY, USA.

ABSTRACT
Task-induced deactivations within the brain's default mode network (DMN) are thought to reflect suppression of endogenous thought processes to support exogenous goal-directed task processes. Older adults are known to show reductions in deactivation of the DMN compared to younger adults. However, little is understood about the mechanisms contributing to functional dysregulation of the DMN in aging. Here, we explored the relationships between functional modulation of the DMN and age, task performance and white matter (WM) microstructure. Participants were 117 adults ranging from 25 to 83 years old who completed an fMRI task switching paradigm, including easy (single) and difficult (mixed) conditions, and underwent diffusion tensor imaging (DTI). The fMRI results revealed an age by condition interaction (β = -0.13, t = -3.16, p = 0.002) such that increasing age affected deactivation magnitude during the mixed condition (β = -0.29, t = -3.24 p = 0.002) but not the single condition (p = 0.58). Additionally, there was a WM by condition interaction (β = 0.10, t = 2.33, p = 0.02) such that decreasing WM microstructure affected deactivation magnitude during the mixed condition (β = 0.30, t = 3.42 p = 0.001) but not the single condition (p = 0.17). Critically, mediation analyses indicated that age-related reductions in WM microstructure accounted for the relationship between age and DMN deactivation in the more difficult mixed condition. These findings suggest that age-related declines in anatomical connectivity between DMN regions contribute to functional dysregulation within the DMN in older adults.

No MeSH data available.


Related in: MedlinePlus