White matter changes and word finding failures with increasing age - PubMed (original) (raw)

White matter changes and word finding failures with increasing age

Emmanuel A Stamatakis et al. PLoS One. 2011.

Abstract

Background: Increasing life expectancy necessitates the better understanding of the neurophysiological underpinnings of age-related cognitive changes. The majority of research examining structural-cognitive relationships in aging focuses on the role of age-related changes to grey matter integrity. In the current study, we examined the relationship between age-related changes in white matter and language production. More specifically, we concentrated on word-finding failures, which increase with age.

Methodology/principal findings: We used Diffusion tensor MRI (a technique used to image, in vivo, the diffusion of water molecules in brain tissue) to relate white matter integrity to measures of successful and unsuccessful picture naming. Diffusion tensor images were used to calculate Fractional Anisotropy (FA) images. FA is considered to be a measure of white matter organization/integrity. FA images were related to measures of successful picture naming and to word finding failures using voxel-based linear regression analyses. Successful naming rates correlated positively with white matter integrity across a broad range of regions implicated in language production. However, word finding failure rates correlated negatively with a more restricted region in the posterior aspect of superior longitudinal fasciculus.

Conclusions/significance: The use of DTI-MRI provides evidence for the relationship between age-related white matter changes in specific language regions and word finding failures in old age.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. Relationships between background measures, scores from the TOT task and age.

The plots show the relationship between: a) age and Shipley scores (r = .62, p<.001), b) age and NART scores (r = .60, p<.001), c) age and TOT rates (r = .44, p<.01), d) age and Know rates (r = −.64, p<.001), e) age and Don't know rates (r = .47, p<.05) and f) Know rates and Shipley scores (r = −.39, p<.05).

Figure 2

Figure 2. Fractional Anisotropy by age and hemisphere: a) Age-related reductions in FA are shown superimposed on a T1-weighted spatially normalized brain scan.

Left side of the axial slices corresponds to left hemisphere. Color bar indicates range of t-scores. b) FA values obtained from all participants are shown plotted as a function of age. Mean FA values were obtained from 10 mm diameter spheres centered at the peaks of the three most significant voxels resulting from the whole brain SPM analysis. (i) −36 −35 −1 (r = −.87, p<.001), (ii) −47 −45 31 (r = −.83, p<.001) (iii) −2 6 −1 (r = −.86, p<.001). c) Cross-hemispheric FA comparisons are shown superimposed on a T1-weighted spatially normalized brain scan. Color bar indicates range of t-scores, with higher values reflecting greater asymmetry.

Figure 3

Figure 3. Fractional anisotropy and performance in the TOT task.

a) Correlations between proportion Know responses from the TOT task and FA are shown superimposed on a T1-weighted spatially normalized brain scan. Color bar indicates range of t-scores. b) Mean FA values for each participant, obtained at the statistical peak of −42 −46 6 are shown plotted against proportion Know responses (r = −.75, p<.001). Mean FA values from each participant were obtained from a 10 mm diameter sphere centered at the peak of the statistically significant cluster. c) FA correlations between proportion TOTs and FA are shown superimposed on a T1-weighted spatially normalized brain scan. Color bar indicates range of t-scores. d) Mean FA values for each participant, obtained at the statistical peak of 41 −48 19 are shown plotted against proportion TOTs (r = −.72, p<.001). Mean FA values from each participant were obtained from a 10 mm diameter sphere centered at the peak of the statistically significant cluster.

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