Social housing protects against age-related working memory decline independently of physical enrichment in rats

Abstract

Longitudinal human studies suggest that as we age, sociality provides protective benefits against cognitive decline. However, little is known about the underlying neural mechanisms. Rodent studies, which are ideal for studying cognition, fail to examine the independent effects of social housing while controlling for physical enrichment in all groups. In this study rats were socially housed (SH) or nonsocial housed (NSH) throughout their lifespan and tested in the radial arm maze to measure working (WM) and reference (RM) memory longitudinally at three ages. In old age exclusively, SH rats made significantly less WM errors than NSH rats, while RM errors did not differ between groups at any age. Anxiety, as assessed behaviorally and physiologically, could not account for the observed differences in WM. These data provide the first evidence that social enrichment alone can prevent age-related WM deficits in spite of the effects of practice seen in longitudinal designs. Importantly, our model will facilitate future investigations into the mechanisms underlying the neuroprotective benefits of sociability in old age.

Cognitive Reserve in Model Systems for Mechanistic Discovery: The Importance of Longitudinal Studies

“…In this case, the number of errors across 9 days of training increased with age such that 26-month rats made more errors than when they were tested at 3 months (Dellu et al, 1997). In another study, both working memory and reference memory improved from adult to middle-age, and decline from middle-age to old age (Templer et al, 2019). To prevent the use of response strategies, which could compensate for a decline in working memory, it is suggested that researchers increase the number of arms from 8 to 12 and control the initial arm selections (Chrobak et al, 1995;Sabolek et al, 2004).…”

“…• Increased number of arms, reduced training prevents the use of response strategies in aged animals (Chrobak et al, 1995;Dellu et al, 1997;Sabolek et al, 2004;Templer et al, 2019). Y-maze Spatial, episodic working memory ↔ Spontaneous alternations with age (Chaney et al, 2018;Neuner et al, 2019b).…”

“…Important for longitudinal studies is research that employed food restriction as a motivation for spatial episodic/working memory (Ando and Ohashi, 1991;Chrobak et al, 1995;Dellu et al, 1997;Sabolek et al, 2004;Templer et al, 2019), vigilance (Muir et al, 1999;Lambourne et al, 2007;Bharmal et al, 2015;Yhnell et al, 2016), and set-shifting (Zhuo et al, 2007), which continue to find age-related cognitive decline. Furthermore, it is possible that once the animals acquire the task in their youth, reinstatement of behavior in middle-age animals will be facilitated, reducing the time of food restriction required to accomplish the testing.…”

“…The weight of evidence supports the idea that interventions associated with better cognitive function are also associated with the maintenance of synaptic plasticity. A handful of longitudinal studies, testing the same animals at multiple ages, indicate beneficial effects on cognition observed for a hypocaloric diet (Algeri et al, 1991) and social housing (Templer et al, 2019). However, these longitudinal studies did not examine biological markers of brain aging.…”

Apoptosis inhibition is involved in improvement of sevoflurane‑induced cognitive impairment following normobaric hyperoxia preconditioning in aged rats

“…In the present study, 20-month-old rats were selected as aged rats. Among the published articles on cognitive dysfunction, the ages of old rats were very different ranging from 18-24 months ( 58-65 ). According to the aforementioned studies, the rats selected by the present study are equivalent to the aged.…”