Modulatory Mechanisms of Object-recognition Memory in the Perirhinal Cortex

Modulatory mechanisms of object-recognition memory in the perirhinal cortex Nicole Gervais, Ph.D. Concordia University, 2014 The present thesis examined whether acetylcholine (ACh) and 17-β estradiol (E2) modulate object-recognition memory (ORM) and perirhinal cortex (PRh) function. ORM was assessed using the Novel-Object Preference (NOP) test or the delayed non-match-to-sample (DNMS) task. The first goal was to investigate whether acetylcholine (ACh) acts via muscarinic receptors (mAChR) in the PRh to modulate novelty preference and novelty-related neuronal activation. Male rats received intra-PRh infusions of a mAChR antagonist or vehicle in the PRh before or after the familiarization phase of the NOP test, then tested 4or 24-hr later. These infusions were also given before novelor familiarobject exploration. The antagonist prevented novelty preference regardless of retention delay and timing of infusion. While novel-object exploration resulted in increased PRh activation, this increase was prevented by mAChR antagonism. These results are consistent with the idea that ACh (via mAChR in the PRh) modulates novelty preference and neuronal activation following novel-object exploration. A second goal was to determine whether intra-PRh modulates ORM and PRh-mediated synaptic plasticity in ovariectomized rats. Intra-PRh infusions of E2 or vehicle were given immediately before, immediately after, or two hours following the familiarization phase of the NOP test. Intra-PRh infusions of E2 or