Long-term memory underlying hippocampus-dependent social recognition in mice

The ability to learn and remember individuals is critical for the stability of social groups. Social recognition reflects the ability of mice to ident ify and remember conspecifics. Social recognition is assessed as a decrease in spontaneous investigation behaviors observed in a mouse reexposed to a familiar conspecific. Our results demonstrate that group-housed mice show s ocial memory for a familiar juvenile when tested immediately, 30 min, 24 h, 3 days, and 7 days after a single 2-min long interaction. Interestingly, c hronic social isolation disrupts long-term, but not 30-min, social memory. Even a 24-h period of isolation disrupts long-term social memory, a result that may explain why previous investigators only observed short-term social memory in individually housed rodents. Although it has no obvious configur al, relational, or spatial characteristics, here we show that social memory shares characteristics of other hippocampus-dependent memories. Ibotenic a cid lesions of the hippocampus disrupt social recognition at 30 min, but no t immediately after training. Furthermore, long-term, but not short-term so cial memory is dependent on protein synthesis and cyclic AMP responsive ele ment binding protein (CREB) function. These results outline behavioral, sys tems, and molecular determinants of social recognition in mice, and they su ggest that it is a powerful paradigm to investigate hippocampal learning an d memory. Hippocampus 2000;10:47-56, (C) 2000 Wiley-Liss, Inc.