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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.


Fractional anisotropy (FA) measured on DTI for younger > older adults at P < 0.05 FWE corrected cluster threshold and clusters with >20 voxels (top panel). Correlation between left insula and left inferior frontal gyrus connectivity and FA (bottom panel).
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brb3495-fig-0004: Fractional anisotropy (FA) measured on DTI for younger > older adults at P < 0.05 FWE corrected cluster threshold and clusters with >20 voxels (top panel). Correlation between left insula and left inferior frontal gyrus connectivity and FA (bottom panel).

Mentions: Older participants had lower FA in bilateral anterior corona radiata and genu of the corpus callosum (Table¬†4, Fig.¬†4). This finding is in keeping with the postero‚Äźanterior white matter atrophy gradient in aging (Nusbaum et¬†al. 2001; Goh 2011). Given that LINS connectivity to LIFG was significantly related to lower error rates, we examined the relationship between this connectivity measure and mean FA extracted from the regions where the older adults had loss of white matter as shown in Table¬†4. There was a significant negative relationship between LINS to LIFG POrb functional connectivity and FA suggesting that increased functional connectivity may be compensating for age‚Äźrelated alterations of white matter (Fig.¬†4). DTI measures did not correlate with task performance (P¬†>¬†0.2 for Pearson's correlation coefficient for all six regions in Table¬†4).


Dominant hemisphere functional networks compensate for structural connectivity loss to preserve phonological retrieval with aging
Fractional anisotropy (FA) measured on DTI for younger > older adults at P < 0.05 FWE corrected cluster threshold and clusters with >20 voxels (top panel). Correlation between left insula and left inferior frontal gyrus connectivity and FA (bottom panel).
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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

brb3495-fig-0004: Fractional anisotropy (FA) measured on DTI for younger > older adults at P < 0.05 FWE corrected cluster threshold and clusters with >20 voxels (top panel). Correlation between left insula and left inferior frontal gyrus connectivity and FA (bottom panel).
Mentions: Older participants had lower FA in bilateral anterior corona radiata and genu of the corpus callosum (Table¬†4, Fig.¬†4). This finding is in keeping with the postero‚Äźanterior white matter atrophy gradient in aging (Nusbaum et¬†al. 2001; Goh 2011). Given that LINS connectivity to LIFG was significantly related to lower error rates, we examined the relationship between this connectivity measure and mean FA extracted from the regions where the older adults had loss of white matter as shown in Table¬†4. There was a significant negative relationship between LINS to LIFG POrb functional connectivity and FA suggesting that increased functional connectivity may be compensating for age‚Äźrelated alterations of white matter (Fig.¬†4). DTI measures did not correlate with task performance (P¬†>¬†0.2 for Pearson's correlation coefficient for all six regions in Table¬†4).

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.