Bilateral brain regions associated with naming in older adults

Abstract

To determine structural brain correlates of naming abilities in older adults, we tested 24 individuals aged 56-79 on two confrontation-naming tests (the Boston Naming Test (BNT) and the Action Naming Test (ANT)), then collected from these individuals structural Magnetic-Resonance Imaging (MRI) and Diffusion Tensor Imaging (DTI) data. Overall, several regions showed that greater gray and white matter volume/integrity measures were associated with better task performance. Left peri-Sylvian language regions and their right-hemisphere counterparts, plus left mid-frontal gyrus correlated with accuracy and/or negatively with response time (RT) on the naming tests. Fractional anisotropy maps derived from DTI showed robust positive correlations with ANT accuracy bilaterally in the temporal lobe and in right middle frontal lobe, as well as negative correlations with BNT RT, bilaterally, in the white matter within middle and inferior temporal lobes. We conclude that those older adults with relatively better naming skills can rely on right-hemisphere peri-Sylvian and mid-frontal regions and pathways, in conjunction with left-hemisphere peri-Sylvian and mid-frontal regions, to achieve their success.

Figure 1

Accuracy and Age on Naming Tasks

Figure 2

RT and Age on Naming Tasks

Figure 3. Gray matter volumes correlated with BNT RT

Flattened cortex visualization of the ROIs for which gray matter volume negatively correlated with BNT reaction times. Visualization was performed with FreeSurfer Software tools. Blue - left middle frontal gyrus Red - left planum temporale

Figure 4. Gray matter volumes correlated with ANT accuracy

Flattened cortex visualization of the ROIs for which gray matter volume negatively correlated with ANT accuracy. Left Hemisphere:

1. Blue - middle frontal gyrus / Green - Inferior temporal gyrus

Right Hemisphere:

1. Blue - middle frontal gyrus /Red - superior frontal gyrus /Green - angular gyrus / Yellow – opercularis / Teal - planum polare / Orange - middle temporal gyrus

Figure 5. White matter density and performance on naming tasks

First row: ANT: Linear regression coefficients relating accuracy (left) and reaction time on correct trials (right) with local white matter density. Second row: BNT: Linear regression coefficients relating accuracy (left) and reaction time on correct trials (right) with local white matter density. Height threshold (uncorr.) and cluster extent threshold (FWE corrected) both at p=.05.

Figure 6. FA (fractional anisotropy) for performance on naming tasks

First row: Linear regression coefficient relating FA and reaction time (correct trials) on BNT, projected onto mean skeletonized FA image. Height threshold T=1.75, p<.05 Cluster extent threshold=314 voxels, p=.05 MNI coordinates are [−41, −17, −11]. Second and third row: Linear regression coefficient relating FA and accuracy on ANT, projected onto mean skeletonized FA image. Height threshold T=1.75, p<.05 (uncorr.) Cluster extent threshold=301 voxels, p=.05 (FWE corrected) Left and right maps show two clusters, MNI coordinates of [−43, −23, −10] and [48, 3, 25], correspondingly.