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White Matter Language Pathways and Language Performance in Healthy Adults Across Ages - PubMed

  • ️Tue Jan 01 2019

White Matter Language Pathways and Language Performance in Healthy Adults Across Ages

James Houston et al. Front Neurosci. 2019.

Abstract

The goal of this study was to determine the relationship between age-related white matter changes, with a specific focus on previously identified language pathways, and language functioning in healthy aging. 228 healthy participants (126 female; 146 right-handed), ages 18 to 76, underwent 3.0 Tesla MR diffusion weighted imaging (DWI) and a battery of language assessments including the Boston Naming Test (BNT), the Peabody Picture Vocabulary Test (PPVT), the Controlled Oral Word Association Test (COWAT), Semantic Fluency Test (SFT), and a subset of the Boston Diagnostic Aphasia Examination (CI-BDAE). Using tract based spatial statistics (TBSS), we investigated measurements of fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD). TBSS was used to create a white matter skeleton that was then used to analyze white matter changes (indexed by FA, AD, RD, and MD) with age and language performance. Results focused primarily on significant relationships (p < 0.05, cluster-wise FDR corrected for multiple comparisons) in the canonical language white matter pathways. We found a diffuse linear decrease with age in global white matter FA and a significant focal increase in FA with age within the bilateral superior cerebellar peduncles (SCPs). We observed that increased BNT scores were associated with increased FA within the left SLF, and within the posterior and antero-lateral portions of the right inferior frontal-occipital fasciculus (IFOF). Increased SFT and PPVT scores were associated with increased FA within the posterior portion of the right IFOF and increased FA within the left body of the corpus callosum was associated with lower COWAT scores. We found no association between FA and BDAE. MD, RD, and AD, were found to be inversely proportional to FA within the IFOF, with AD showing a negative correlation with SFT, and RD and MD showing a negative correlation with BNT. There was no association between CI-BDAE and any of the white matter measures. Significant differences between sexes included more pronounced FA decrease with age within the right SLF in males vs. females; there were no differences in language performance scores between sexes. We also found that there was no decline in language testing scores with increasing age in our cohort. Taken together, our findings of varying relationships between DTI metrics and language function within multiple regions of the non-dominant IFOF suggest that more robust language networks with bilateral structural connectivity may contribute to better overall language functioning, regardless of age.

Keywords: diffusion MRI; fractional anisotropy; inferior fronto-occipital fasciculus; tract based spatial statistics; white matter language pathways.

Copyright © 2019 Houston, Allendorfer, Nenert, Goodman and Szaflarski.

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Figures

FIGURE 1
FIGURE 1

Linear fit between age and behavioral scores. For each behavioral score, linear fit of data with 95% prediction interval is depicted. In addition, R2 and p-values of regression analysis between age and score is provided.

FIGURE 2
FIGURE 2

Significant correlations between FA and behavioral scores (p < 0.05, cluster-wise FDR corrected for multiple comparisons). (A) FA shows positive relationships with BNT, PPVT, and SFT performance and a negative relationship with COWAT performance. (B) Significant correlations between FA and BNT, SFT, and PPVT overlap in a region of the right inferior fronto-occipital fasciculus. Pictures are in neurological convention with left side in the figure corresponding to the left side of the brain.

FIGURE 3
FIGURE 3

Significant correlations between SFT scores and AD values (p < 0.05, cluster-wise FDR corrected for multiple comparisons). Pictures are in neurological convention with left side in the figure corresponding to the left side of the brain.

FIGURE 4
FIGURE 4

Significant correlations between COWAT scores and (A) AD and (B) RD values (p < 0.05, cluster-wise FDR corrected for multiple comparisons). Pictures are in neurological convention with left side in the figure corresponding to the left side of the brain.

FIGURE 5
FIGURE 5

Significant correlations between BNT scores and (A) MD and (B) RD values (p < 0.05, cluster-wise FDR corrected for multiple comparisons). Pictures are in neurological convention with left side in the figure corresponding to the left side of the brain.

FIGURE 6
FIGURE 6

Significant correlations between (A) FA decrease with age and (B) FA increase with age (p < 0.05, cluster-wise FDR corrected for multiple comparisons). Pictures are in neurological convention with left side in the figure corresponding to the left side of the brain.

FIGURE 7
FIGURE 7

Significant correlations between (A) RD increase with age and (B) RD decrease with age (p < 0.05, cluster-wise FDR corrected for multiple comparisons). Pictures are in neurological convention with left side in the figure corresponding to the left side of the brain.

FIGURE 8
FIGURE 8

Significant correlations between (A) MD increase with age and (B) AD decrease with age (p < 0.05, cluster-wise FDR corrected for multiple comparisons). Pictures are in neurological convention with left side in the figure corresponding to the left side of the brain.

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