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Author Notes:

Corresponding author: Jessica Raper, Ph.D., Yerkes National Primate Research Center, 954 Gatewood Rd NE, Atlanta, GA 30329, jraper@emory.edu, Phone: 404-727-8334

Acknowledgments: Authors are grateful to Christen Merte, Patrick McFarland, Cassie Lyon, Sara Dicker, and Rebecca Roberts, M.A., for their invaluable assistance running the Human Intruder paradigm, animal handling, mother–infant reunions, and reintroductions to the social group.

We also thank all members of the Bachevalier Laboratory who have helped with the neuroimaging and surgical procedures on the infant monkeys.

The content is solely the responsibility of the authors and does not necessarily represent the official view of the NIMH, or the National Institutes of Health.

The YNPRC is fully accredited by the American for the Assessment and Accreditation of Laboratory Care, international.


Research Funding:

This research was supported by the National Institute for Mental Health (MH050268).

The studies were also supported by the Center for Behavioral Neuroscience (NSF IBN 9876754), and Integrated Training in Psychobiology and Psychopathology Fellowship (NIMH T32 MH73525), as well as by the National Center for Research Resources to the Yerkes National Research Center (P51 RR00165; YNRC Base grant), which is currently supported by the Office of Research Infrastructure Programs/OD P51OD11132.


  • sex difference
  • amygdala
  • emotion
  • cortisol
  • testosterone

Sex-dependent role of the amygdala in the development of emotional and neuroendocrine reactivity to threatening stimuli in infant and juvenile rhesus monkeys


Journal Title:

Hormones and Behavior


Volume 63, Number 4


, Pages 646-658

Type of Work:

Article | Post-print: After Peer Review


Amygdala dysfunction and abnormal fear and stress reactivity are common features of several developmental neuropsychiatric disorders. Yet, little is known about the exact role the amygdala plays in the development of threat detection and emotional modulation. The current study examined the effects of neonatal amygdala lesions on defensive, emotional, and neuroendocrine reactivity of infant rhesus monkeys reared with their mothers in large species-typical social groups. Monkeys received either bilateral MRI-guided ibotenic acid amygdala (Neo-A; n = 16) or sham (Neo-C; n = 12) lesions at 24.8 ± 1.2 days of age, or served as behavioral control (Neo-BC; n = 3). Defensive and emotional responses were assessed using the Human Intruder Paradigm as infants and as juveniles (2.5 and 12 months of age, respectively), whereas neuroendocrine reactivity was only examined during the juvenile period. As infants, Neo-A animals expressed similar levels of freezing and hostile behaviors as compared to controls, whereas during the juvenile period Neo-A animals expressed significantly less freezing compared to controls. Interestingly, the sex of the infant modulated the behavioral effects of neonatal amygdalectomy, leading to different patterns of behavior depending on the sex and lesion status of the infant. Unlike controls, Neo-A infants did not modulate their behavioral responses based on the salience of the threat. The impact of neonatal amygdalectomy increased with age, such that Neo-A juveniles exhibited fewer emotional behaviors and increased cortisol response to the stressor as compared to controls. These data indicate that the amygdala plays a critical role in the development of both emotional and neuroendocrine reactivity as well as the expression of sexually dimorphic emotional expression.

Copyright information:

© 2012 Elsevier Inc. All rights reserved.

This is an Open Access work distributed under the terms of the Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported License (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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