Spontaneous recognition in rats : synaptic plasticity and neurodevelopmental challenge
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Disruptions in memory are a hallmark feature of several psychiatric diseases. These illnesses are often marred by an inability to recognize that a stimulus or event as been previously experienced, a phenomenon known as recognition memory. Previous study has demonstrated that cognitive disruptions reflect aberrant signaling, including disruptions in synaptic plasticity, in key regions of the brain, such as prefrontal cortex (PFC), hippocampus, and perirhinal cortex (PRh). However, in the case of recognition memory, how these disruptions arise and what specific plasticity mechanisms are involved is less clear. An understanding of the etiological factors underlying disruption and the synaptic processes involved in recognition will greatly advance the treatment and prevention of psychiatric disorders. As a result, the present thesis examined recognition memory in rodents in two experiments. In the first experiment, we blocked the endocytosis of AMPA receptors during the encoding, consolidation, or retrieval phase of object recognition memory using local PRh infusions of the cell membrane permeable Tat-GluA23Y interference peptide. Tat-GluA23Y infusion before the encoding and consolidation phases did not alter memory. In contrast, Tat-GluA23Y infusion prior to the retrieval phase significantly disrupted memory. These results indicate a distinct role for AMPA receptor endocytosis during a specific phase (retrieval) of visual recognition memory. In the second experiment, pregnant dams were treated with PolyI:C (4mg/kg, i.v.) on gestational day (GD) 15, and both the male and female offspring of these rats were tested as young adults in three different recognition memory tests: spontaneous novel object recognition, novel object location recognition, and object-in-place recognition. Male, but not female, rats were impaired in an object-in-place memory test that depends on processing between medial temporal lobe and PFC. However, neither male nor female rats were impaired on tests of simpler discriminations dependent on the medial temporal lobe. These findings support clinical studies demonstrating impaired object location binding in clinical populations and further demonstrate the plausibility of prenatal immune activation as an etiological factor in neurodevelopmental disease. Taken together, these results highlight the importance of a specific form of synaptic plasticity during the recognition of familiar stimuli and demonstrate that early life adversity can disrupt recognition memory processes.
DegreeMaster of Science (M.Sc.)
SupervisorHowland, John G.
CommitteePaterson, Phyllis G.; West, Nigel H.; Fisher, Thomas E.; Desautels, Michel; Mulligan, Sean J.
prenatal immune activation