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Dominant hemisphere functional networks compensate for structural connectivity loss to preserve phonological retrieval with aging

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: Loss of hemispheric asymmetry during cognitive tasks has been previously demonstrated in the literature. In the context of language, increased right hemisphere activation is observed with aging. Whether this relates to compensation to preserve cognitive function or dedifferentiation implying loss of hemispheric specificity without functional consequence, remains unclear.

Methods: With a multifaceted approach, integrating structural and functional imaging data during a word retrieval task, in a group of younger and older adults with equivalent cognitive performance, we aimed to establish whether interactions between hemispheres or reorganization of dominant hemisphere networks preserve function. We examined functional and structural connectivity on data from our previously published functional activation study. Functional connectivity was measured using psychophysiological interactions analysis from the left inferior frontal gyrus (LIFG) and the left insula (LINS), based on published literature, and the right inferior frontal gyrus (RIFG) based on our previous study.

Results: Although RIFG showed increased activation, its connectivity decreased with age. Meanwhile, LIFG and LINS connected more bilaterally in the older adults. White matter integrity, measured by fractional anisotropy (FA) from diffusion tensor imaging, decreased significantly in the older group. Importantly, LINS functional connectivity to LIFG correlated inversely with FA.

Conclusions: We demonstrate that left hemispheric language areas show higher functional connectivity in older adults with intact behavioral performance, and thus, may have a role in preserving function. The inverse correlation of functional and structural connectivity with age is in keeping with emerging literature and merits further investigation with tractography studies and in other cognitive domains.

No MeSH data available.


Left insula PPI for older > younger adults at P < 0.001 uncorrected voxel threshold with clusters >20 voxels.
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brb3495-fig-0002: Left insula PPI for older > younger adults at P < 0.001 uncorrected voxel threshold with clusters >20 voxels.

Mentions: From the LINS (x = −30, y = 20, z = −14) seed region, connectivity results are shown in Table 3. For the older group, left insula connected to both left and right hemispheric areas, namely, LIFG POrb and LIFG PTri, left and right middle frontal gyri, right superior frontal gyrus and right caudate region. No significant connectivity was seen in younger adults from left insula. In a subtractive analysis between the two groups using a two sample t‐test, no differences were found at the FWE corrected threshold, but at P < 0.001 uncorrected threshold, higher insular connectivity for the older group was found with LIFG POrb, right middle frontal gyrus, LINS, left middle frontal, and left fusiform gyrus (Fig. 2). No significant negative interactions were found.


Dominant hemisphere functional networks compensate for structural connectivity loss to preserve phonological retrieval with aging
Left insula PPI for older > younger adults at P < 0.001 uncorrected voxel threshold with clusters >20 voxels.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036427&req=5

brb3495-fig-0002: Left insula PPI for older > younger adults at P < 0.001 uncorrected voxel threshold with clusters >20 voxels.
Mentions: From the LINS (x = −30, y = 20, z = −14) seed region, connectivity results are shown in Table 3. For the older group, left insula connected to both left and right hemispheric areas, namely, LIFG POrb and LIFG PTri, left and right middle frontal gyri, right superior frontal gyrus and right caudate region. No significant connectivity was seen in younger adults from left insula. In a subtractive analysis between the two groups using a two sample t‐test, no differences were found at the FWE corrected threshold, but at P < 0.001 uncorrected threshold, higher insular connectivity for the older group was found with LIFG POrb, right middle frontal gyrus, LINS, left middle frontal, and left fusiform gyrus (Fig. 2). No significant negative interactions were found.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: Loss of hemispheric asymmetry during cognitive tasks has been previously demonstrated in the literature. In the context of language, increased right hemisphere activation is observed with aging. Whether this relates to compensation to preserve cognitive function or dedifferentiation implying loss of hemispheric specificity without functional consequence, remains unclear.

Methods: With a multifaceted approach, integrating structural and functional imaging data during a word retrieval task, in a group of younger and older adults with equivalent cognitive performance, we aimed to establish whether interactions between hemispheres or reorganization of dominant hemisphere networks preserve function. We examined functional and structural connectivity on data from our previously published functional activation study. Functional connectivity was measured using psychophysiological interactions analysis from the left inferior frontal gyrus (LIFG) and the left insula (LINS), based on published literature, and the right inferior frontal gyrus (RIFG) based on our previous study.

Results: Although RIFG showed increased activation, its connectivity decreased with age. Meanwhile, LIFG and LINS connected more bilaterally in the older adults. White matter integrity, measured by fractional anisotropy (FA) from diffusion tensor imaging, decreased significantly in the older group. Importantly, LINS functional connectivity to LIFG correlated inversely with FA.

Conclusions: We demonstrate that left hemispheric language areas show higher functional connectivity in older adults with intact behavioral performance, and thus, may have a role in preserving function. The inverse correlation of functional and structural connectivity with age is in keeping with emerging literature and merits further investigation with tractography studies and in other cognitive domains.

No MeSH data available.