Neural Pathways Modulating Memory Consolidation

University Of Iowa, Iowa City IA

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Abstract

? DESCRIPTION (provided by applicant): Prior studies examining multiple memory systems in the brain have had great difficulty elucidating the specific neural connections that influence the consolidation and synaptic plasticity for different kinds of learning. The present proposal will utilize optogenetic manipulations of specific pathways connecting different brain regions in rats immediately after the rats have undergone different kinds of learning. Specifically, this proposal will build upon the evidence that the basolateral amygdala (BLA) influences consolidation for many different kinds of learning, including spatial/contextual, emotional, and cued-response learning, whereas other regions are involved in memory for more discrete forms of learning. Additional evidence indicates that the BLA influences consolidation through regulation of synaptic plasticity in these other brain regions, including modulation of activity-regulated cytoskeletal-associated protein (Arc), which has been shown to mediate some of the BLA's effects on memory consolidation. Based on these prior findings, the present studies will investigate how distinct BLA projections to different parts of the hippocampus and caudate modulate memory consolidation and Arc expression in downstream brain regions following different kinds of learning. Follow-up experiments will determine whether the increased Arc expression is necessary for the memory modulation. To do so, the current proposal will utilize optogenetic control of activity in specific BLA projections immediately after different learning tasks to directly examine in each Aim: 1) how the candidate pathways influence consolidation for the specific type of learning and 2) how the pathways influence Arc expression in downstream regions and whether the Arc expression is necessary for the memory modulation. Aim 1 will determine how BLA projections to different parts of the hippocampal formation influence consolidation and Arc expression for the context vs. footshock learning in a modified contextual fear conditioning task. Aim 2 will determine how BLA projections to part of the hippocampal formation and the caudate influence consolidation and Arc expression for spatial vs. cued-response learning. In both aims, optogenetic stimulation/inhibition will be given to each candidate pathway immediately after the relevant training to determine its role in influencing consolidation. Moreover, each aim will examine whether such optogenetic manipulations alter Arc expression in different downstream structures and whether reducing Arc levels in those regions prevents the memory-modulating effects of the optogenetic manipulations, providing a critical complementary set of experiments that will improve our model for understanding how the BLA influences memory and plasticity-related proteins such as Arc in other regions. The findings from these studies will provide, for the first time, knowledge for how the specific pathways from the BLA to other brain regions influence memory consolidation and synaptic plasticity. Moreover, these experiments will provide a first step to creating an understanding of the functional connections within the brain underlying consolidation processes.