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. 2009 Jan;30(1):228-40.
doi: 10.1002/hbm.20497.

Aging and the Interaction of Sensory Cortical Function and Structure

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Free PMC article

Aging and the Interaction of Sensory Cortical Function and Structure

Ann M Peiffer et al. Hum Brain Mapp. .
Free PMC article

Abstract

Even the healthiest older adults experience changes in cognitive and sensory function. Studies show that older adults have reduced neural responses to sensory information. However, it is well known that sensory systems do not act in isolation but function cooperatively to either enhance or suppress neural responses to individual environmental stimuli. Very little research has been dedicated to understanding how aging affects the interactions between sensory systems, especially cross-modal deactivations or the ability of one sensory system (e.g., audition) to suppress the neural responses in another sensory system cortex (e.g., vision). Such cross-modal interactions have been implicated in attentional shifts between sensory modalities and could account for increased distractibility in older adults. To assess age-related changes in cross-modal deactivations, functional MRI studies were performed in 61 adults between 18 and 80 years old during simple auditory and visual discrimination tasks. Results within visual cortex confirmed previous findings of decreased responses to visual stimuli for older adults. Age-related changes in the visual cortical response to auditory stimuli were, however, much more complex and suggested an alteration with age in the functional interactions between the senses. Ventral visual cortical regions exhibited cross-modal deactivations in younger but not older adults, whereas more dorsal aspects of visual cortex were suppressed in older but not younger adults. These differences in deactivation also remained after adjusting for age-related reductions in brain volume of sensory cortex. Thus, functional differences in cortical activity between older and younger adults cannot solely be accounted for by differences in gray matter volume.

Figures

Figure 1
Figure 1
Voxel-based morphometry (VBM) results within visual cortex: Middle-aged adults had greater gray matter volume than older adults in right BA17 and left superior BA18. When young and older adults were compared, these areas remained significant and expanded to show bilateral differences in both BA17 and 19. These were identified within a ROI of visual responsive cortex and used intracranial volume as a covariate and a FWE correction (P < 0.05) for multiple comparisons.
Figure 2
Figure 2
Visual task response differences. Axial slices depict clusters where young adults have significantly more activity than older adults in right BA18. To graphically depict the regression by age results, activity within the 28,−84,10 MNI coordinate voxel is shown. Interestingly, this voxel falls within the cluster identified in the ANOVA group results.
Figure 3
Figure 3
Biological parametric mapping (BPM) ANCOVA results for visual task activity difference between young and older adults: BPM results indicate that the increased fMRI activation in younger compared with older adults for the visual stimuli remains when differences in gray matter volume from voxel-based morphometry (VBM) are accounted for in the analysis. It is interesting to note that the area involved in functional differences does not show a significant gray matter volume difference in the VBM analysis, but greater gray matter volume in young adults can be seen at subthreshold levels in this area in the uncorrected VBM map.
Figure 4
Figure 4
Auditory task response in occipital cortex: Clusters depicted on axial brain sections were identified as significant in the regression of age and BOLD signal, and the signal from the peak voxel is graphically depicted within the scatter plot. Blue spectrum colors depict the negative regression where deactivation activity is associated with older age (peak voxel −36,−92,−5 MNI coordinate), whereas red spectrum colors show areas identified in the positive regression that have deactivation activity associated with younger age (peak voxel 40,−76,−15 MNI coordinate). Between age group analyses identified similar cortical areas as in the regression analyses. Within the superior BA18 area, older adults tended to deactivate while younger adults activated. This was reversed within the inferior BA18 cluster where younger adults tended to deactivate and older adults activated. These same areas showed significant differences between older and middle-aged adults as well.

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