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Unravelling the temporal role of hippocampal subareas on contextual fear memory retrieval and discrimination

Grant number: 17/18939-2
Support type:Scholarships abroad - Research Internship - Scientific Initiation
Effective date (Start): November 21, 2017
Effective date (End): February 20, 2018
Field of knowledge:Humanities - Psychology
Principal Investigator:Raquel Vecchio Fornari
Grantee:Moisés dos Santos Corrêa
Supervisor abroad: Erika Atucha Trevino
Home Institution: Centro de Matemática, Computação e Cognição (CMCC). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
Local de pesquisa : Leibniz Institute for Neurobiologie (LIN), Germany  
Associated to the scholarship:15/26983-6 - Effects of different shock intensities during the contextual fear conditioning training on plasma corticosterone levels and the contextual memory specificity in rats, BP.IC

Abstract

Learning situations prompt changes in neurons and synapses in several encephalic areas. The changes that happen in these different brain regions are called memory consolidation. At first, the main theory on systems memory consolidation was called the standard model. This model suggests that contextual memories start the consolidation process in the hippocampus and, after some time, the consolidated memories migrate to the neocortex, making the retrieval of these memories independent from the hippocampus. Subsequent data suggested, nonetheless, that the hippocampus still keeps an active role in the retrieval of some remote memories, which means that, as time goes by, the retrieval of contextual memories indeed activate many neocortical neurons, but, differently from what the standard model proposed, the hippocampus' neurons are still activated. This model is called the Multiple-trace Theory. However, little is known about the individual roles each hippocampal subarea plays in the consolidation and retrieval of recent and remote memories. Some studies suggest that CA1 maintains an ongoing involvement with the retrieval of memories while CA3's involvement diminishes over time. On the other hand, computer models predict that CA3 is more involved with the pattern completion aspect of memory retrieval, it being critical for memory discrimination. Here we propose to investigate the functional relevance of CA1 and CA3 sub regions during contextual fear memory consolidation as well as their possible role in memory discrimination. Either CA1 or CA3 will be inactivated with optogenetics during the retrieval test, using the training context and a novel one, one day after the fear conditioning training. Hippocampal activity will be measured with the quantification of arc+ cells using the fluorescent in situ hybridization technique. The results in this project will further ascertain the neurobiology of contextual memory evocation and discrimination. (AU)