Right fronto-parietal networks mediate the neurocognitive benefits of enriched environments.

Abstract

Exposure to enriched environments (EE) throughout a lifetime, providing so called reserve, protects against cognitive decline in later years. It has been hypothesised that high levels of alertness necessitated by EE might strengthen the right fronto-parietal networks (FPN) to facilitate this neurocognitive resilience. We have previously shown that EE offset age-related deficits in selective attention by preserving grey matter within right fronto-parietal regions. Here, using neurite orientation dispersion and density imaging (NODDI), we examined the relationship between EE, microstructural properties of fronto-parietal white matter association pathways (three branches of the superior longitudinal fasciculus, SLF), structural brain health (atrophy), and attention (alertness, orienting and executive control) in a group of older adults. We show that EE is associated with a lower orientation dispersion index (ODI) within the right SLF1 which in turn mediates the relationship between EE and alertness, as well as grey- and white-matter atrophy. This suggests that EE may induce white matter plasticity (and prevent age-related dispersion of axons) within the right FPN to facilitate the preservation of neurocognitive health in later years.

Evidence accumulation rate moderates the relationship between enriched environment exposure and age-related response speed declines

“…Specifically, a number of studies have shown that connectivity within the fronto-parietal networks (FPN) accounts for substantial inter-individual variability in neurocognitive resilience in older adults (e.g. (Brosnan et al, 2021;Franzmeier et al, 2017aFranzmeier et al, , 2017bVeldsman et al, 2020)). Recently, we have shown in healthy younger adults that individual differences in connectivity within the dorsal FPN (white matter macrostructural organisation of the superior longitudinal fasciculus (SLF), and resting state functional connectivity within the dorsal FPN) varied according to the CPP build-up rate (Brosnan et al, 2020).…”

“…Recently, we have shown in healthy younger adults that individual differences in connectivity within the dorsal FPN (white matter macrostructural organisation of the superior longitudinal fasciculus (SLF), and resting state functional connectivity within the dorsal FPN) varied according to the CPP build-up rate (Brosnan et al, 2020). In older adults, increasing evidence suggests that the SLF varies according to both levels of EE (Brosnan et al, 2021), and risk factors for neurocognitive decline (e.g. (Veldsman et al, 2020)).…”