Lesions to the <scp>CA</scp>2 region of the hippocampus impair social memory in mice

<jats:title>Abstract</jats:title><jats:p>The function of the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region of the hippocampus is poorly understood. Although the <jats:styled-content style="fixed-case">CA</jats:styled-content>1 and <jats:styled-content style="fixed-case">CA</jats:styled-content>3 regions have been extensively studied, for years the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region has primarily been viewed as a linking area between the two. However, the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region is known to have distinct neurochemical and structural features that are different from the other parts of the hippocampus and in recent years it has been suggested that the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region may play a role in the formation and/or recall of olfactory‐based memories needed for normal social behavior. Although this hypothesis has been supported by hippocampal lesion studies that have included the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region, no studies have attempted to specifically lesion the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region of the hippocampus in mice to determine the effects on social recognition memory and olfaction. To fill this knowledge gap, we sought to perform excitotoxic <jats:italic><jats:styled-content style="fixed-case">N</jats:styled-content></jats:italic>‐methyl‐<jats:styled-content style="fixed-case">D</jats:styled-content>‐aspartate lesions of the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region and determine the effects on social recognition memory. We predicted that lesions of the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region would impair social recognition memory. We then went on to test olfaction in <jats:styled-content style="fixed-case">CA</jats:styled-content>2‐lesioned mice, as social memory requires a functional olfactory system. Consistent with our prediction, we found that <jats:styled-content style="fixed-case">CA</jats:styled-content>2‐lesioned animals had impaired social recognition. These findings are significant because they confirmed that the <jats:styled-content style="fixed-case">CA</jats:styled-content>2 region of the hippocampus is a part of the neural circuitry that regulates social recognition memory, which may have implications for our understanding of the neural regulation of social behavior across species.</jats:p>