The impact of long-term social housing on biconditional association task performance and neuron ensembles in the anterior cingulate cortex and the hippocampal CA3 region of aged rats.

Cognitive decline and changes in neuronal activity are hallmarks of aging. While environmental enrichment (EE) can protect against cognitive deficits in old age, whether EE with long-term social housing provides greater protection than EE alone, and the underlying neuronal mechanisms, remain unknown. Here, aged socially housed (SH), aged non-socially housed (NSH), and young rats were tested on the biconditional association task (BAT), a test of cognitive flexibility in which the rewarded object depends on the subjects' location in a Y maze. Immediate early genes were used to assess neuronal activity during BAT performance and a working memory alternation task in which rats traversed the arms of the Y maze but were not required to select the correct object on either side of the maze. NSH rats had significantly impaired working memory compared to SH rats and significantly impaired performance on BAT compared to both young and SH rats, indicating that social housing protects cognitive flexibility during aging beyond EE alone. SH rats displayed greater CA3 hippocampal activity during BAT, and lower anterior cingulate cortex activity during the alternation task compared to NSH rats, suggesting that neuronal activity differences in these regions may explain preserved cognition in SH animals.