Brain networks activated to form object recognition memory.

Object recognition memory allows discrimination of familiar and novel objects. Previous studies have shown the importance of several brain regions for object recognition memories; however, the mechanisms underlying the consolidation of object recognition (OR) memory at the anatomic level remain unknown. Here, we analyzed the brain network for the generation of OR memory in mice by measuring the expression of the immediate-early gene c-fos. We found that c-fos expression was induced in the hippocampus (CA1 and CA3 regions), insular cortex (IC), perirhinal cortex (PRh), and medial prefrontal cortex (mPFC) when OR memory was generated, suggesting that gene expression in these brain regions contributes to the formation of OR memory. Consistently, inhibition of protein synthesis in the mPFC blocked the formation of long-term OR memory. Importantly, network analyses suggested that the hippocampus, IC, PRh and mPFC show increased connectivity with other brain regions when OR memory is formed. Thus, we suggest that a brain network composed of the hippocampus, IC, PRh, and mPFC is required for the generation of OR memory by connecting with other brain regions.