Effects of Selective Neonatal Amygdala Lesions on Flexible Response Selection in Adult Rhesus Macaques Open Access

Shen, Jiaqi Grace (Spring 2021)

Permanent URL: https://etd.library.emory.edu/concern/etds/3r074w12f?locale=en


Recent developmental studies in monkeys show neonatal-onset lesions of the amygdala alter food choice guided by reward value but not choice guided by reward contingency. To build on this study, the same animals with neonatal lesions of the amygdala were tested to assess their Food/Non-food selection strategy with or without satiation. The behavioral tasks measure the animals’ selection of Food and Non-food items (Experiment 1), and their ability to switch selection of preferred food towards other preferred food after satiation using the Primary Reinforcer Devaluation paradigm (Experiment 2). We hypothesized that adult monkeys with neonatal neurotoxic amygdala lesions will show an increased preference of Non-food items over regular food items as compared to control animals that will disregard these Non-food items and intact satiation response. The findings showed that neurotoxic neonatal amygdala lesions did not affect food selection in adult rhesus macaques and spared the ability to flexibly switch their selection strategy after satiation. Thus, both early-onset and adult-onset amygdala lesions had no effects on the abilities to select palatable foods over inedible foods and to modulate food selection after satiation. These results are at odd with previous reports indicating that the amygdala lesioned animals had a tendency to select more inedible objects and showed heightened meat preference. Future studies are needed to explore other neural structures related to food preferences and modulation of food intake disruption that are observed in Autism Spectrum Disorders as well as the role of amygdala in emotional appraisal in patients with bulimia and binge eating disorders. 

Table of Contents

1. Introduction 1

1.1 Brain regions implicated in the modulation of food intake 2

1.2 Amygdala neuroanatomical and connectional system 3

1.3 Role of the amygdala in food intake modulation 5

1.4 Role of the amygdala in the development of food intake modulation 8

2. Methods 9

2.1 Subjects 9

2.2 Neuroimaging 10

2.3 Surgery 11

2.4 Sham operations in Group Neo-C 12

2.5 MRI - based and histological lesion evaluation 12

2.6 Behavioral paradigm apparatus 13

2.6.1 Experiment 1: Food/ Non-food Preference 13

2.6.2 Experiment 2: Primary Reinforcer Devaluation 14

2.7 Data analysis 15

3. Results 17

3.1 Histological verification of lesions 17

3.2 Effects of Neonatal amygdala lesions on food preference and devaluation 18

3.2.1 Experiment 1 18

3.2.2 Experiment 2 19

3.3 Effects of Adult amygdala lesions on food preference and devaluation 21

3.3.1 Experiment 1 21

3.3.2 Experiment 2 22

3.4 Comparisons between the effects of neonatal amygdala lesions and adult-onset amygdala lesions on food preference 24

4. Discussion 25

4.1 The effects of amygdala lesions on food preference 26

4.2 Effects of neonatal and adult-onset amygdala lesions on Primary Reinforcer Devaluation 30

5. Summary 31

References 33

Figures 42

Tables 51

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