The Medial Prefrontal Cortex is Involved in Social Odor Recognition Memory

Objective The medial prefrontal cortex (mPFC) is critical to mediating attention and social cognition, but its specific role in memory processing is unclear. In a rodent model of social odor recognition memory (SORM), we assessed the role of the prelimbic and infralimbic regions of the mPFC in social motivation and recognition memory at different stages of the memory process (encoding, consolidation, and retrieval). In the same animals, we also assessed the role of these subregions of the mPFC in sustained attention, using the rodent psychomotor vigilance test (rPVT). Methods The SORM task involves three phases (familiarization, habituation, and recognition), and requires olfactory‐based discrimination between familiar odors and novel odors from conspecifics, where failure to show preference for novel odors on the test phase indicates a memory deficit. The rPVT is a sustained attention test that measures accuracy, premature responding, and response times to the presence of a stimulus light that appears after a random waiting period between 3–10 seconds. Using pAAV‐hSyn‐hM4D(Gi)‐mCherry (“designer receptors,” DREADDs) injected bilaterally into the prelimbic or infralimbic regions of the mPFC, we remotely silenced these regions during behavioral testing via injections of the “designer drug,” clozapine‐N‐oxide (CNO). Results For the SORM test, injecting CNO (1 mg/kg, i.p.) 30 minutes prior to the habituation phase did not impair novel odor discrimination on this phase, but did result in impaired memory for a novel odor on the recognition test day 24‐hrs later. These effects were not a function of CNO administration alone because the impairment was found on the drug‐free test day 24‐hrs after the previous CNO injection. In a second study, injections of CNO (0–5 mg/kg, i.p.) were administered 30‐min prior to different rPVT sessions. CNO at 1 mg/kg had effects on premature responding in the rPVT, without impairing response times. Conclusions Silencing the prelimbic and infralimbic subregions of the mPFC impaired memory performance the recognition test phase of the SORM test, without inducing a motor impairment in the psychomotor vigilance test, indicating that the mPFC could be involved in encoding, and possibly consolidating, information about social odors acquired during habituation. Support or Funding Information This work was supported by a grant from NASA (NNX15AC71G) to CMD. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .