# Semantic and Phonological Brain Networks in Older Adults: A Systematic Scoping Review

## TL;DR

This review found that semantic and phonological brain networks in older adults are similar to those in younger adults, but with subtle differences, supporting theories of cognitive aging.

## Contribution

The study systematically reviews semantic and phonological brain networks in older adults, highlighting their consistency with younger adults but with implications for cognitive aging theories.

## Key findings

- Semantic and phonological regions in older adults align with ventral and dorsal stream pathways as in younger adults.
- Subtle differences in brain network organization were observed between older and younger adults.
- Findings support the CRUNCH/de-differentiation hypothesis over HAROLD/PASA models of cognitive aging.

## Abstract

What are the main findings?
In our scoping review of older adult studies, we found similarities with regions implicated in semantic and phonological processing in younger adults.Regions with the potential for semantic and phonological specialization in older adults were largely confined to the ventral and dorsal stream pathways, respectively.

In our scoping review of older adult studies, we found similarities with regions implicated in semantic and phonological processing in younger adults.

Regions with the potential for semantic and phonological specialization in older adults were largely confined to the ventral and dorsal stream pathways, respectively.

What are the implications of the main findings?
The results of this scoping review are generally compatible with the CRUNCH or de-differentiation hypothesis.Complementary activation- and lesion-based meta-analyses in older adults are recommended.

The results of this scoping review are generally compatible with the CRUNCH or de-differentiation hypothesis.

Complementary activation- and lesion-based meta-analyses in older adults are recommended.

Background/Objectives: Despite many neurobiological models of semantics and phonology, there is no consensus regarding their functional organization. Specifically, there is considerable debate concerning the precise functional roles of the left inferior frontal gyrus and inferior parietal lobe, where these two networks may overlap. Meta-analyses addressing this topic have focused on neurologically intact young adults, yet theories of cognitive aging suggest older adults may exhibit a different distribution of their language networks. This scoping review specifically explores the interplay between semantic and phonological neural networks in older adults. Methods: Following the PRISMA extension guidelines, we carried out a systematic search to identify relevant primary research. Thirty-seven studies were included, representing a range of populations (e.g., neurologically intact older adults, post-stroke aphasia), methodologies (e.g., task-based functional magnetic resonance imaging, lesion symptom mapping), and sample sizes from 11 to 1231 participants. Results: Based on the number of studies identifying relationships with a given region, we found that regions potentially specialized for semantics or phonology and those potentially subserving both domains are largely consistent with networks derived from meta-analyses of younger adults. However, we found subtle differences between older and younger adults. Conclusions: Our results are generally compatible with the CRUNCH or de-differentiation perspectives of cognitive aging. In our characterization of the literature related to the semantic and phonological networks of older adults, we did not see a pattern consistent with the HAROLD or PASA models, though our findings were limited by methodological decisions. Our work suggests that future complementary activation- and lesion-based meta-analyses are warranted to more precisely delineate the semantic and phonological networks in older adults.