Limits...
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.


Parametric model with Reaction time (RT) applied to PPI analysis from left insula (−30, 20, −14) showing negative correlations (at P < 0.001 uncorrected and >20 voxels) between functional connectivity and RT.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5036427&req=5

brb3495-fig-0003: Parametric model with Reaction time (RT) applied to PPI analysis from left insula (−30, 20, −14) showing negative correlations (at P < 0.001 uncorrected and >20 voxels) between functional connectivity and RT.

Mentions: We also applied a parametric model for RT to the three seed region PPI analyses. While no correlations were found at the FWE corrected threshold of P < 0.05 and over 20 voxels, we found a negative correlation in the LINS PPI model with RT as a regressor. The region of significance here was in the left frontal area (left middle frontal gyrus −34, 58, 2) as shown in Figure 3.


Dominant hemisphere functional networks compensate for structural connectivity loss to preserve phonological retrieval with aging
Parametric model with Reaction time (RT) applied to PPI analysis from left insula (−30, 20, −14) showing negative correlations (at P < 0.001 uncorrected and >20 voxels) between functional connectivity and RT.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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

brb3495-fig-0003: Parametric model with Reaction time (RT) applied to PPI analysis from left insula (−30, 20, −14) showing negative correlations (at P < 0.001 uncorrected and >20 voxels) between functional connectivity and RT.
Mentions: We also applied a parametric model for RT to the three seed region PPI analyses. While no correlations were found at the FWE corrected threshold of P < 0.05 and over 20 voxels, we found a negative correlation in the LINS PPI model with RT as a regressor. The region of significance here was in the left frontal area (left middle frontal gyrus −34, 58, 2) as shown in Figure 3.

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.