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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

Relationship of age and DMN WM microstructure with task-induced deactivation. The scatter plots show DMN deactivation magnitude in the single and mixed conditions (greater positive values = greater deactivation) plotted against age (A,B) and FA in the DMN-WM mask (C,D). Neither age (A) nor FA in the DMN-WM mask (C) correlated with task-induced deactivation in the single condition. Age (B) was negatively correlated and FA in the DMN-WM mask (D) was positively correlated with deactivation magnitude in the mixed condition. Dashed lines represent the linear best fit of the data. R2 values indicate the portion of the total variance explained by the line.
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Figure 2: Relationship of age and DMN WM microstructure with task-induced deactivation. The scatter plots show DMN deactivation magnitude in the single and mixed conditions (greater positive values = greater deactivation) plotted against age (A,B) and FA in the DMN-WM mask (C,D). Neither age (A) nor FA in the DMN-WM mask (C) correlated with task-induced deactivation in the single condition. Age (B) was negatively correlated and FA in the DMN-WM mask (D) was positively correlated with deactivation magnitude in the mixed condition. Dashed lines represent the linear best fit of the data. R2 values indicate the portion of the total variance explained by the line.

Mentions: There were significant main effects of Age (β = −0.48, t = −2.56, p = 0.01) and Condition (β = 0.14, t = 3.47, p = 0.001) such that increasing age and the single condition were associated with less deactivation. There was also a significant Age × Condition interaction (β = −0.13, t = −3.16, p = 0.002). Examination of this interaction (Figures 2A,B) indicated that age was not related to DMN deactivation in the single condition (p = 0.58), but was significantly correlated in the mixed condition (β = −0.29, t = −3.24 p = 0.002).


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)

Relationship of age and DMN WM microstructure with task-induced deactivation. The scatter plots show DMN deactivation magnitude in the single and mixed conditions (greater positive values = greater deactivation) plotted against age (A,B) and FA in the DMN-WM mask (C,D). Neither age (A) nor FA in the DMN-WM mask (C) correlated with task-induced deactivation in the single condition. Age (B) was negatively correlated and FA in the DMN-WM mask (D) was positively correlated with deactivation magnitude in the mixed condition. Dashed lines represent the linear best fit of the data. R2 values indicate the portion of the total variance explained by the line.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Relationship of age and DMN WM microstructure with task-induced deactivation. The scatter plots show DMN deactivation magnitude in the single and mixed conditions (greater positive values = greater deactivation) plotted against age (A,B) and FA in the DMN-WM mask (C,D). Neither age (A) nor FA in the DMN-WM mask (C) correlated with task-induced deactivation in the single condition. Age (B) was negatively correlated and FA in the DMN-WM mask (D) was positively correlated with deactivation magnitude in the mixed condition. Dashed lines represent the linear best fit of the data. R2 values indicate the portion of the total variance explained by the line.
Mentions: There were significant main effects of Age (β = −0.48, t = −2.56, p = 0.01) and Condition (β = 0.14, t = 3.47, p = 0.001) such that increasing age and the single condition were associated with less deactivation. There was also a significant Age × Condition interaction (β = −0.13, t = −3.16, p = 0.002). Examination of this interaction (Figures 2A,B) indicated that age was not related to DMN deactivation in the single condition (p = 0.58), but was significantly correlated in the mixed condition (β = −0.29, t = −3.24 p = 0.002).

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