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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 deactivation magnitude with REACTION TIME (RT) in the mixed condition. RT in the mixed condition was positively correlated with age (A) and negatively correlated with deactivation magnitude (B). Dashed lines are the linear best-fit line. R2 is the portion of the total variance explained by the regression line.
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Figure 3: Relationship of age and DMN deactivation magnitude with REACTION TIME (RT) in the mixed condition. RT in the mixed condition was positively correlated with age (A) and negatively correlated with deactivation magnitude (B). Dashed lines are the linear best-fit line. R2 is the portion of the total variance explained by the regression line.

Mentions: Results of the GLMs examining the effects of age, FA, and deactivation magnitude on task performance are presented in Table 3. There were main effects of both age and FA in the DMN-WM mask on task performance (accuracy and RT). There was a significant Age × Condition interaction for accuracy. Examination of this interaction indicated that accuracy was only marginally correlated with age during the single condition (p = 0.09), but was significantly correlated with age during the mixed condition (β = −0.24, t = −2.68, p = 0.008). There were also marginal Age × Condition and Deactivation magnitude × Condition interactions for RT. Examination of these interactions (Figure 3) indicated that age was correlated with RT in both the single (β = 0.51, t = 6.38, p < 0.001) and mixed (β = 0.46, t = 5.62 p < 0.001) condition, while deactivation magnitude was correlated with RT in the mixed condition (β = −0.21, t = −2.32 p = 0.02) but not the single condition (p = 0.75).


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 deactivation magnitude with REACTION TIME (RT) in the mixed condition. RT in the mixed condition was positively correlated with age (A) and negatively correlated with deactivation magnitude (B). Dashed lines are the linear best-fit line. R2 is the portion of the total variance explained by the regression line.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: Relationship of age and DMN deactivation magnitude with REACTION TIME (RT) in the mixed condition. RT in the mixed condition was positively correlated with age (A) and negatively correlated with deactivation magnitude (B). Dashed lines are the linear best-fit line. R2 is the portion of the total variance explained by the regression line.
Mentions: Results of the GLMs examining the effects of age, FA, and deactivation magnitude on task performance are presented in Table 3. There were main effects of both age and FA in the DMN-WM mask on task performance (accuracy and RT). There was a significant Age × Condition interaction for accuracy. Examination of this interaction indicated that accuracy was only marginally correlated with age during the single condition (p = 0.09), but was significantly correlated with age during the mixed condition (β = −0.24, t = −2.68, p = 0.008). There were also marginal Age × Condition and Deactivation magnitude × Condition interactions for RT. Examination of these interactions (Figure 3) indicated that age was correlated with RT in both the single (β = 0.51, t = 6.38, p < 0.001) and mixed (β = 0.46, t = 5.62 p < 0.001) condition, while deactivation magnitude was correlated with RT in the mixed condition (β = −0.21, t = −2.32 p = 0.02) but not the single condition (p = 0.75).

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