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.


Second level subtractive analysis for words > baseline contrast for old > young groups (P < 0.005, uncorrected).
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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

brb3495-fig-0001: Second level subtractive analysis for words > baseline contrast for old > young groups (P < 0.005, uncorrected).

Mentions: Second level analysis for the words > rest has been reported previously (Geva et al. 2012). Additionally, we performed an exploratory second level analysis for words > baseline to explore the role of left hemisphere language areas based on published literature on phonology. We used a lower statistical threshold (P < 0.005) to identify seed regions for PPI analysis, given the preexisting evidence regarding role of these areas, particularly the left insula (Wise et al. 1999; Cereda et al. 2002; Shafto et al. 2007; Papoutsi et al. 2011), in phonological processing. The exploratory analysis was performed with the single aim of picking seed regions for connectivity analysis and is not otherwise applied for our hypothesis testing. These results at an exploratory threshold of P < 0.005 uncorrected are shown in Figure 1.


Dominant hemisphere functional networks compensate for structural connectivity loss to preserve phonological retrieval with aging
Second level subtractive analysis for words > baseline contrast for old > young groups (P < 0.005, uncorrected).
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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

brb3495-fig-0001: Second level subtractive analysis for words > baseline contrast for old > young groups (P < 0.005, uncorrected).
Mentions: Second level analysis for the words > rest has been reported previously (Geva et al. 2012). Additionally, we performed an exploratory second level analysis for words > baseline to explore the role of left hemisphere language areas based on published literature on phonology. We used a lower statistical threshold (P < 0.005) to identify seed regions for PPI analysis, given the preexisting evidence regarding role of these areas, particularly the left insula (Wise et al. 1999; Cereda et al. 2002; Shafto et al. 2007; Papoutsi et al. 2011), in phonological processing. The exploratory analysis was performed with the single aim of picking seed regions for connectivity analysis and is not otherwise applied for our hypothesis testing. These results at an exploratory threshold of P < 0.005 uncorrected are shown in Figure 1.

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.