Mnemonic processes require precise coordination between diverse neural substrates
Creators: name: Nanu, Roshan Devan
Publisher: name: Brandeis University
Year: 2021
Subjects: amygdala
hippocampus
learning
memory
Stk11
thalamus
Behavioral sciences
Human Learning and Memory

description: Learning and memory are hallmark functions of the brain that central to animals’ ability to adapt and survive. These processes are known to involve, and often require, many separate neural structures; however, much neuroscience research views individual brain areas as discrete computational units each extracting or transforming specific information before passing it on to another system, and studies into memory --- or any neural process --- often involve silencing a region or a connection to see its involvement in the behavior. In actuality, multiple brain regions are constantly processing information and communicating in tandem, and real-world dysfunction rarely involves the complete failure of any single region or pathway. More often, it is small alterations in protein function, connectivity or firing patterns that sum to produce dysfunctional brain states. These often manifest as pronounced behavioral deficits such as those seen in Alzheimer's disease, schizophrenia, and numerous other neurological disorders; the most damaging of which often involve impairments in learning and memory function. As such, we need a better understanding of how diverse neural substrates function in concert to facilitate these processes, and how subtler alterations affect them.
description: This thesis takes this viewpoint as it examines several studies in which perturbations --- not silencing --- of inter-region communication impair learning in the hopes of highlighting that (A) these brains regions do not process information in isolation and (B) inter-region communication requires precise timing to carry out mnemonic tasks with any fidelity. Chapter 1 provides a road map of this thesis as well as a general review of prior work leading up to and informing the studies presented in chapters 2 and 3. These investigations each explore a different type of memory with chapter 2 detailing an investigation into the interactions between the hippocampus and the thalamic nucleus reuniens during working memory tasks, while chapter 3 explores interactions between gustatory cortex and the basolateral amygdala over the course of taste aversion learning, a form of long-term memory. Each of these chapters starts with its own abstract specific to the study reported therein. In both cases, as discussed in chapter 4, we see that disruptions in the timing of inter-region communications, while largely preserving the information content from the perturbed region, still impair proper expression of the memory in question. Together these results showcase the importance of proper coordination between brain regions for memory processes, regardless of the time-scale, neural substrates or modality of the memories. Furthermore, they open up new avenues of research that can help us better understand how learning occurs in the brain, and how small perturbations in neural function can lead to profound impairments with learning and memory.