Social isolation impacts late-life socio-cognitive decline in APP/PS1 mice

In this study the effects of social isolation (SI) were investigated in APP/PS1 mice. It was found that SI during adolescence has an impact on anxiogenic behaviour, such that isolated animals tend to explore a threatening environment less than non-isolated animals as assessed with the EPM test, and that this holds for both AD and non-AD mice. While no evidence was found for any differences in short-term memory as assessed by the Y-maze, long-term memory seemed to be affected in a context-dependent manner. Object memory as assessed with the NOR test was affected in APP/PS1 mice compared to WT mice, but this deficit was not induced or influenced by SI. When it comes to social recognition memory however, we found that SI exacerbated the social memory deficit in AD mice, and even induced a deficit in WTs. Associative fear memory as assessed with the PA test suggested that WTs perform better when group housed, and APP/PS1 mice better when socially isolated. The link between isolation and AD, or cognition in general, may be more complex than initially thought. The effect of isolation may not be the same for AD versus non-AD subjects.