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Author Notes:

Correspondence: Mar Sanchez, Ph.D., Dept. of Psychiatry & Behavioral Sciences and Yerkes National Primate Research Center, 954 Gatewood Rd NE, Atlanta, GA 30329; Email: mmsanch@emory.edu; Phone: 404-712-2393

Acknowledgments: Authors are grateful to Amy Henry, Trina Villarreal, Shannon Stephens, M.A., Christen Merte, Patrick McFarland, Cassie Lyons, Rebecca Roberts, M.A., and Sara Dicker for their invaluable assistance with handling mother–infant reunions, reintroductions to the social groups as well as data collection.

We also thank all members of the Bachevalier Laboratory who have helped with the neuroimaging and surgical procedures on the infant monkeys and Sarah Pruett, PhD in the Yerkes BioMarker Core Laboratory for assistance with the hormone assays.

Disclosures: None of the authors have any conflicts of interest in the conduct or reporting of this research.

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 MH732505), 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.


  • amygdala
  • HPA axis
  • testosterone
  • sex difference

Neonatal amygdala lesions alter basal cortisol levels in infant rhesus monkeys


Journal Title:



Volume 38, Number 6


, Pages 818-829

Type of Work:

Article | Post-print: After Peer Review


The amygdala is mostly thought to exert an excitatory influence on the hypothalamic-pituitary-adrenal (HPA) axis, although its role regulating HPA basal tone is less clear, particularly during primate development. The current study examined the effects of neonatal amygdala lesions on basal HPA function and the postnatal testosterone (T) surge of rhesus monkeys reared with their mothers in large outdoor social groups. An early morning basal blood sample was collected at 2.5 months of age, whereas at 5 months samples were collected not only at sunrise, but also at mid-day and sunset to examine the diurnal rhythm of cortisol. At 2.5 months of age sham-operated males exhibited higher cortisol than females, but this sex difference was abolished by neonatal amygdalectomy, with lesioned males also showing lower basal cortisol than controls. Although neonatal amygdalectomy did not alter the postnatal T surge, there was a positive relationship between T and basal cortisol levels. At 5 months of age, neither the sex difference in cortisol, nor its correlation with T levels were apparent any longer. Instead, the diurnal cortisol rhythm of both males and females with amygdalectomy showed a blunted decline from mid-day to sunset compared to controls. These results indicate that neonatal amygdala damage alters basal HPA function in infant rhesus monkeys, affecting males only at early ages (at 2.5 months), while leaving the postnatal T surge intact, and resulting in a flattened diurnal rhythm in both genders at the later ages. Thus, the primate amygdala has a critical influence on the HPA axis in the first few months of life.

Copyright information:

© 2012 Elsevier Ltd. 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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