Temporal dynamics of corticosterone induced modulation of emotional memory endurance and specificity

Abstract

In recent years, Neuroscience has advanced in the understanding of how memories are formed, but little is known about how they are stored and evoked. Memories of events with strong emotional content tend to be well remembered and evidence points to the importance of the hormones released by the adrenal cortex gland (cortisol in humans and corticosterona, in rats) in modulating the consolidation of these memories. The corticosterone acts in different brain regions, including the hippocampus, the basolateral complex of the amygdala and some cortical regions to enhance memory consolidation of various tasks, including context fear conditioning. A variety of evidence indicates that the hippocampus plays a limited role in processing memory and with the passage of time it stabilizes and is transferred to be stored in the neocortex. Despite some differences in the literature, some studies also show that contextual memory become less specific and more generalized over time, which could be the result of memory trace transfer from hippocampus to other brain areas. Although there is extensive evidence that emotional experiences reinforce the permanence of memories for long periods of time, there are no studies that have investigated the temporal dynamics of the modulation of specificity and endurance of emotional memory by corticosterone. This project aims to investigate the effects of corticosterone on the specificity and duration of emotional memory in the task of context fear conditioning in rats. Corticosterone systemic injections will be held immediately after the training in this task, and the animals will be tested in the context of training and in a new context after 48 hours (recent memory) or 28 days (remote memory). Furthermore, the possible involvement of various brain regions such as hippocampus, amygdala and cerebral cortex in the modulation of contextual fear conditioning memory, both recent and remote, corticosterone induced will also be analyzed by the expression of Fos protein. The results may contribute to increase our knowledge about the neural circuitry involved in the effects of emotion and/or alert regarding the formation and maintenance of long-term memory, as well as revealing the time course of activation of different brain structures involved in this process. (AU)