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Nonnavigational Spatial Memory Processing in the Medial Temporal Lobe and Goal-Directed Behavior in Rhesus Macaques

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Nonnavigational Spatial Memory Processing in the Medial Temporal Lobe and Goal-Directed Behavior in Rhesus Macaques NONNAVIGATIONAL SPATIAL MEMORY PROCESSING IN THE MEDIAL TEMPORAL LOBE AND GOAL-DIRECTED BEHAVIOR IN RHESUS MACAQUES A Dissertation submitted to the Faculty of the Graduate School of Arts and Sciences of Georgetown University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Pharmacology By Elyssa M. LaFlamme, B.A. Washington, DC February 7, 2020 Copyright 2020 by Elyssa M. LaFlamme All Rights Reserved ii NONNAVIGATIONAL SPATIAL MEMORY PROCESSING IN THE MEDIAL TEMPORAL LOBE AND GOAL-DIRECTED BEHAVIOR IN RHESUS MACAQUES Elyssa M. LaFlamme, B.A. Thesis Advisor: Ludise Malkova, Ph.D., Patrick A. Forcelli, Ph.D. , ABSTRACT The hippocampus and cortical areas of the medial temporal lobe have a critical role in navigational spatial memory, as has been well-established in rodent models. However, nonnavigational spatial memory is more difficult to evaluate in rodents, and it is unknown whether it shares the same neural substrates. Nonhuman primates offer a more suitable translational model. The Hamilton Search Task, adapted for monkeys, is a behavioral assay for nonnavigational spatial memory in which animals are required to track self-generated selections from a linear array of boxes baited with hidden food rewards. Perfect performance entails visiting each box only once without repeating. This task is sensitive to loss of hippocampal function. Experiment 1 investigated the hypothesis that pharmacological inactivation of the parahippocampal cortex would also impair task performance, as the parahippocampal cortex is a major source of spatial input to the hippocampus. Bilateral microinfusion of glutamate receptor antagonist kynurenic acid in the parahippocampal cortex, but not unilateral microinfusion, profoundly and selectively impaired nonnavigational spatial memory across long delays. Furthermore, contralateral inactivation of the parahippocampal cortex in one hemisphere and the hippocampus in the opposite hemisphere also impaired iii performance, indicating that the hippocampal-parahippocampal pathway is critical for nonnavigational memory. Experiment 2 investigated the hypothesis that cholinergic blockade in the hippocampus would also impair performance, but in fact, bilateral microinfusion of neither nicotinic antagonist mecamylamine nor muscarinic antagonist scopolamine affected Hamilton Search Task performance. In rodent models, extended training in stimulus-reward paradigms can prevent animals from shifting their behavior to reflect changes in reward value. This represents a shift away from goal-directed decision-making into instrumental, habit-directed behavior, which makes it a useful experimental model for the overreliance on habit often found in addiction and other neuropsychiatric disorders. However, this loss of devaluation effect after overtraining has been difficult to reproduce in humans. Experiment 3 investigated the effect of extended training with concurrent visual discriminations on reinforcer devaluation in rhesus macaques. Not only was reinforcer devaluation unaffected by overtraining for hundreds of trials, but this study offered evidence that extended training may even correct for biases produced by attentional habit. vi ACKNOWLEDGMENTS My sincere and boundless gratitude… To my mentors, Drs. Ludise Malkova and Patrick Forcelli, for your patience and trust and for all the ways you helped me to grow as a scientist. You gave me the best possible grad school experience, and any success I find will be thanks to you. To our veterinarians, Drs. Patricia Foley and Robin Tucker, for keeping the monkeys happy and healthy and for teaching me how to do the same. To my support team in the Translational Biomedical Sciences Program, especially Dr. Kathryn Sandberg and Emily Bujold, for your unwavering encouragement and mentorship and for always pushing me one more step forward. To the best labmate of all time, Hannah Waguespack, for the cakes and the company, for facing the grind with me head-on, and for making me laugh even on the hardest days. To my lab elders, Drs. Brittany Aguilar and Catherine Elorette, for teaching me everything I know about monkeys and for being the kind of team (and podcast club) I was excited to work with every day. To my science soulmate, Meezah Ehtesham, for always reminding me why I love research. To my best friend, Lindsey Osburnsen, for being my home base, my greatest support, and my inspiration for almost a decade; and to Goose, who (probably) can’t read but deserves to be thanked anyway for gracing me with his presence. To my parents, Sheri Diffely and Jamie LaFlamme, and my sister, May LaFlamme, for a foundation of unconditional support and indefatigable humor. Once upon a time, you let me believe I could fly, and I did. To my grandma, Linda Diffely, for a lifetime supply of cookies, books, theater, laughter, and unconditional support. You have always been my greatest role model and my number one champion. And to my grandpa, Bob Diffely, for all the bedtime stories about outer space and quantum physics and for giving me my first science books. You are the reason I fell in love with science in the first place and the reason I believed in myself in a world still trying to convince us that science is not for girls. You are dearly missed. “Our prime obligation to ourselves is to make the unknown known. We are on a journey to keep an appointment with whatever we are.” ~Gene Roddenberry vii TABLE OF CONTENTS Chapter I: The Parahippocampal Cortex and Hippocampal-Parahippocampal Interactions in Nonnavigational Spatial Memory ................................................ 1 1.1 Introduction .................................................................................................. 1 1.2 Methods ..................................................................................................... 40 1.3 Results ....................................................................................................... 52 1.4 Discussion ................................................................................................. 70 Chapter II: Hippocampal Cholinergic Transmission in Nonnavigational Spatial Memory ............................................................................................................ 80 2.1 Introduction ................................................................................................ 80 2.2 Methods ..................................................................................................... 87 2.3 Results ....................................................................................................... 90 2.4 Discussion ................................................................................................. 94 Chapter III: Reinforcer Devaluation and Habit Formation by Extended Training ............................................................................................................ 97 3.1 Introduction ................................................................................................ 97 3.2 Methods ................................................................................................... 105 3.3 Results ..................................................................................................... 115 3.4 Discussion ............................................................................................... 123 Chapter IV: General Discussion ........................................................................ 128 4.1 Discussion ............................................................................................... 128 References ........................................................................................................ 137 v LIST OF FIGURES Figure 1.1: Microinfusion site targeting and verification ....................................... 54 Figure 1.2: Hamilton Search Task performance after bilateral inactivation of the parahippocampal cortex ...................................................................................... 59 Figure 1.3: Hamilton Search Task performance after bilateral inactivation of the hippocampus ....................................................................................................... 62 Figure 1.4: Hamilton Search Task performance after crossed-inactivation of the contralateral hippocampus and parahippocampal cortex .................................... 64 Figure 1.5: Hamilton Search Task performance after unilateral inactivation of the parahippocampal cortex ...................................................................................... 67 Figure 1.6: Hamilton Search Task performance after unilateral inactivation of the hippocampus ....................................................................................................... 68 Figure 2.1: Hamilton Search Task performance after cholinergic receptor blockade in the hippocampus .............................................................................. 93 Figure 3.1: Reinforcer preference across probe sessions ................................. 117 Figure 3.2: Devaluation index as a function of training cycle and relative object history ................................................................................................................ 119 Figure 3.3: Devaluation index as a function of cumulative training .................... 120 Figure 3.4: Difference score as a function of training cycle and relative object history ...............................................................................................................
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