Increased functional connectivity supports language performance in healthy aging despite gray matter loss

Abstract

Although language is quite preserved from aging, it remains unclear whether age-related differences lead to a deterioration or reorganization in language functional networks, or to different dynamics with other domains (e.g., the multiple-demand system). The present study is aimed at examining language networks, using resting-state functional magnetic resonance imaging in typical aging in relation to language performance. Twenty-three (23) younger adults and 24 healthy older adults were recruited. Volumetric gray matter differences between the 2 groups were assessed using voxel-based morphometry. Then, seed-based analyses, integrated local correlations in core regions of the language network, and within- and between-network connectivity were performed. We expected less extended connectivity maps, local coherence diminution, and higher connectivity with the multiple-demand system in older adults. On the contrary, analyses showed language network differences in healthy aging (i.e., increased connectivity with areas inside and outside language network), but no deterioration, despite widespread atrophy in older adults. Integrated local correlation revealed alterations that were unnoticeable with other analyses. Although gray matter loss was not correlated with language performance, connectivity differences were positively correlated with fluency performance in the older group. These results differ from the literature concerning other cognitive networks in aging in that they show extra internetwork connections without a decrease in intranetwork language connections. This reorganization could explain older adults' good language performance and could be interpreted in accordance with the scaffolding theory of aging and cognition.

Keywords: Aging; Functional connectivity; Language; Resting-state; fMRI.