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Brain Structure and Function

, Volume 220, Issue 5, pp 2705–2720 | Cite as

Global versus tract-specific components of cerebral white matter integrity: relation to adult age and perceptual-motor speed

  • Micah A. Johnson
  • Michele T. Diaz
  • David J. Madden
Original Article

Abstract

Although age-related differences in white matter have been well documented, the degree to which regional, tract-specific effects can be distinguished from global, brain-general effects is not yet clear. Similarly, the manner in which global and regional differences in white matter integrity contribute to age-related differences in cognition has not been well established. To address these issues, we analyzed diffusion tensor imaging measures from 52 younger adults (18–28) and 64 older adults (60–85). We conducted principal component analysis on each diffusion measure, using data from eight individual tracts. Two components were observed for fractional anisotropy: the first comprised high loadings from the superior longitudinal fasciculi and corticospinal tracts, and the second comprised high loadings from the optic radiations. In contrast, variation in axial, radial, and mean diffusivities yielded a single-component solution in each case, with high loadings from most or all tracts. For fractional anisotropy, the complementary results of multiple components and variability in component loadings across tracts suggest regional variation. However, for the diffusivity indices, the single component with high loadings from most or all of the tracts suggests primarily global, brain-general variation. Further analyses indicated that age was a significant mediator of the relation between each component and perceptual-motor speed. These data suggest that individual differences in white matter integrity and their relation to age-related differences in perceptual-motor speed represent influences that are beyond the level of individual tracts, but the extent to which regional or global effects predominate may differ between anisotropy and diffusivity measures.

Keywords

Aging Diffusion tensor imaging Fractional anisotropy Cognition Mediation 

Abbreviations

AC-PC

Anterior commissure–posterior commissure

AD

Axial diffusivity

CST

Corticospinal tract

DTI

Diffusion tensor imaging

DWI

Diffusion-weighted image

fSPGR

Fast spoiled gradient-echo imaging

FA

Fractional anisotropy

FMRIB

Functional MRI of the brain

FOV

Field of view

ICA

Independent component analysis

MD

Mean diffusivity

MNI

Montreal Neurological Institute

MR

Magnetic resonance

MRI

Magnetic resonance imaging

OR

Optic radiations

PCA

Principal component analysis

RD

Radial diffusivity

RF

Radio frequency

ROI

Region of interest

RT

Reaction time

SFNR

Signal fluctuation to noise ratio

SLF

Superior longitudinal fasciculus

SNR

Signal to noise ratio

TE

Echo time

TR

Repetition time

WAIS

Wechsler Adult Intelligence Scale

Notes

Acknowledgments

This research was supported by grants R01 AG034138 (MTD) and R01 AG039684 (DJM) from the National Institute on Aging. We thank Guy Potter, Ying-hui Chou, Emily L. Parks, David A. Hoagey, Sally Ann B. Cocjin, and Maxwell Horowitz for assistance. We also thank the staff and scientists at the Brain Imaging and Analysis Center, especially the center director, Allen W. Song, for their support of this project.

Supplementary material

429_2014_822_MOESM1_ESM.jpg (70 kb)
Supplementary material 1 (JPEG 70 kb)
429_2014_822_MOESM2_ESM.doc (44 kb)
Supplementary material 2 (DOC 43 kb)

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© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Micah A. Johnson
    • 1
  • Michele T. Diaz
    • 1
    • 2
  • David J. Madden
    • 1
    • 2
  1. 1.Brain Imaging and Analysis CenterDuke University Medical CenterDurhamUSA
  2. 2.Department of Psychiatry and Behavioral SciencesDuke University Medical CenterDurhamUSA

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