Effects of Maternal Care on Amygdala, Prefrontal Cortex, and Hippocampal Development in Infant Rhesus Monkeys Open Access

Fu, Caroline Lucy (2015)

Permanent URL: https://etd.library.emory.edu/concern/etds/bc386j766?locale=en


Childhood maltreatment is a devastating experience with significant emotional and neurobiological consequences. It is prevalent not only in humans, but also in non-human primates, including rhesus monkeys. Non-human primate models serve as excellent models for studying effects of maltreatment, as they allow experimental manipulations of subjects that cannot be performed in humans. The rhesus monkey, due to its highly complex social structure and strong and long-lasting mother-infant bonds, is an animal model of high translational value for human experience. This study seeks to investigate the effects of infant maltreatment on structural development of the infant brain, focusing primarily on the amygdala, prefrontal cortex (PFC), and hippocampus because of their critical roles on the regulation of emotional and stress responses. Another goal of the study is to examine whether exposure to elevated levels of the stress hormone cortisol induced by the maltreatment experience predicts the structural impact on those cortico-limbic regions. This study utilizes a cross-fostering experimental design, with random assignment to experimental group, where some offspring were cross-fostered to control mothers and others to maltreating mothers, to control for the potential effects of genetic and/or epigenetic factors transmitted by biological mothers. Brain structural development was studied at 6 and 12 months (infancy and transition to the juvenile period), including intracranial volume (defined as total white matter + total gray matter + total ventricular and subarachnoid cerebrospinal fluid-CSF), total white matter, gray matter, and CSF volumes, as well as amygdalar, PFC, and hippocampal volumes. We found decreased amygdalar and PFC gray matter and CSF volumes as a result of maltreatment and positive correlations between amygdalar volume and PFC gray matter and early cortisol levels. However, we found no effects on the hippocampus. These findings suggest that maltreatment-related neurodevelopmental effects emerge during infancy but that the impact (presence, directionality, magnitude) is different depending on the brain region, potentially due to their different patterns of development and time needed to respond to stress, supporting the critical role of timing of the experience and of the measurement of the effects of stress on neural volumes.

Table of Contents

Introduction 1

Methods 7

Subjects and Housing 7

Cross-fostering design 8

Structural MR Brain Image Acquisition 9

Hair Cortisol Samples 12

Statistical Analysis 12

Results 14

Total Brain, White Matter, Gray Matter, and CSF Volumes 14

Amygdala 15

Prefrontal Cortex (PFC) 17

Hippocampus 22

Hair Cortisol Data 24

Discussion 40

Literature Cited 49

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