The Role of the Amygdala in Memory for Social and Nonsocial Odors Open Access

Abstract

The Role of the Amygdala in Memory for Social and Nonsocial Odors By Sujith Swarna

Background: The basolateral amygdala (BLA) plays a key role in memory enhancement for emotional events. However, it is unclear how the BLA plays a role in modulating affective salience or the motivational significance of a stimulus to an individual. Because social information carries more affective salience than nonsocial information, the BLA may play a role in the prioritization of social information but not nonsocial information.

Purpose: The purpose of this project is to investigate the relationship between the BLA and social recognition memory. The project also assesses the role of the BLA in preferences for social stimuli.

Methods: A group of nine female Long Evans rats performed novel odor recognition tasks using other female social odors or nonsocial odors. These subjects also performed in a habituation- dishabituation task to new female social or nonsocial odors. Finally, preference tests were conducted to assess the preferences of these females for a) female social and nonsocial odors and b) female social and male social odors. Prior to each of these tasks, the BLAs of these subjects were infused with either muscimol or saline.

Results: Two-tailed paired-samples t-tests suggest that BLA inhibition may result in impairment of recognition memory performance in nonsocial trials on the NOR task. Three-way repeated measures ANOVA showed a significant effect of trial number in the habituation-dishabituation task as well as a significant interaction of trial number and odor type. Finally, two-tailed one- sample t-tests suggested no preference for female social odors over nonsocial odors in the preference test, but a strong preference for male odors over female odors. A two-tailed paired- samples t-test found that BLA inhibition significantly increased male preference.

Conclusion: The affective salience of an object is one of the primary influences of exploratory behavior in rodents. As such, levels of exploration serve as a good measure of the affective salience of a stimulus. This project suggests that BLA inhibition results in dysregulation of affective salience attribution that causes the rodents to explore objects abnormally more or less than they typically would. 

Table of Contents

Introduction.......................................................................................................................................... 1

The Prioritization of Memory .............................................................................................................. 1

The Amygdala and Emotional Memory ............................................................................................... 1

The Amygdala and Social Cognition .................................................................................................... 2

Experiment 1 ........................................................................................................................................ 4

Method ................................................................................................................................................ 4

Results ................................................................................................................................................. 7

Interim Discussion............................................................................................................................... 9

Experiment 2 ...................................................................................................................................... 10

Method............................................................................................................................................... 10

Results................................................................................................................................................ 11

Interim Discussion............................................................................................................................. 12

Experiment 3 ...................................................................................................................................... 12

Method............................................................................................................................................... 12

Results................................................................................................................................................ 13

Interim Discussion............................................................................................................................. 13

Experiment 4 ...................................................................................................................................... 14

Method............................................................................................................................................... 14

Results................................................................................................................................................ 14

Interim Discussion............................................................................................................................. 15

General Discussion...............................................................................................................................15

References .......................................................................................................................................... 19

Figure Captions ...................................................................................................................................25

Figures .................................................................................................................................................27

Figure 1. BLA inhibition in novel odor recognition memory task with immediate test. .................... 27

Figure 2. BLA inhibition in novel odor recognition memory task with 5-minute test. ...................... 28

Figure 3. BLA inhibition in habituation/dishabituation to social and nonsocial stimuli.................... 29

Figure 4. The role of the BLA in social preference. ............................................................................ 30

Figure 5. The role of the BLA in male versus female preference. ....................................................... 31 

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Neuroscience
Keyword	memory hippocampus amygdala neuroscience
Committee Chair / Thesis Advisor	Dr. Joseph Manns, Emory University
Committee Members	Dr. Michael Crutcher, Emory University Dr. Aubrey Kelly, Emory University

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