Familiarity Discrimination in Rhesus Macaques with Neonatal Perirhinal Lesions Open Access

Abstract

Studies in both humans and monkeys have demonstrated that the perirhinal cortex (PRh) is involved in recognition memory. However, the consequences of neonatal perirhinal lesions on recognition memory later in adulthood are not fully understood. Differences in performance seen on recognition memory tasks (better performance on VPC than DNMS) have suggested that differences in the length of familiarization time between the two tasks may be responsible for their different outcomes. To test this possibility, we tested monkeys with neonatal perirhinal lesions (Neo-PRh) on the Constant Negative task. In this task, animals were presented with repeated familiarization trials of 60 unrewarded objects. The 60 unrewarded objects (constant negatives) were paired with novel objects every testing day. As testing proceeded, the constant negative objects became familiar over the course several testing days and preference for the novel objects on each trial was used as a measure of familiarity. Neo-PRh animals made a similar number of errors compared to controls before reaching criteria. However, Neo-PRh monkeys needed significantly more trials to reach criteria than control animals. In addition, Neo-PRh animals had a slower rate of learning compared to control animals. Finally, a significant correlation was found between the number of Constant Negative trials needed to reach criteria and DNMS performance at a 30 second delay. Overall, the results suggest that early damage to the PRh causes deficits in recognition memory in adulthood and that repeated familiarization trials may be needed to overcome these deficits in the absence of a functional PRh. The present findings give us some insight on memory deficits seen in human cases of temporal lobe epilepsy.

Table of Contents

I. Introduction. 1

II. Methods. 6

a. Subjects. 6

b. Neuroimaging and surgical procedures. 6

c. Lesion Reconstruction. 7

d. Constant Negative Task. 8

e. Data Analysis. 9

III. Results. 10

a. Lesion Assessment. 10

b. Relationship between extent of damage and performance. 10

c. Constant Negative Performance. 11

d. DNMS Correlations. 12

IV. Discussion. 12

V. References. 15

VI. Table 1. 20

VII. Table 2. 21

VIII. Figure 1. 22

IX. Figure 2. 23

X. Figure 3. 24

XI. Figure 4. 25

XII. Figure 5. 26

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	BS
Submission	Honors Thesis
Language	English
Research Field	Biology, Neuroscience
Keyword	Perirhinal Familiarity Lesion
Committee Chair / Thesis Advisor	Bachevalier, Jocelyne, Emory University
Committee Members	Kazama, Andrew Masami, Emory University Cafferty, Patrick William, Emory University

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