Elsevier

Behavioural Brain Research

Volume 229, Issue 2, 15 April 2012, Pages 433-437
Behavioural Brain Research

Short communication
Amygdala volume predicts patterns of eye fixation in rhesus monkeys

https://doi.org/10.1016/j.bbr.2012.01.009Get rights and content

Abstract

In both human and nonhuman primates the eyes are a highly salient feature of the face, conveying identity, emotion and attentional direction of conspecifics. Studies have indicated that the amygdala plays an important role in eye contact, and amygdala dysfunction may underlie social deficits in disorders such as autism through effects on eye contact. In the present study we compared the volume of the amygdala in 32 juvenile rhesus monkeys to visual fixation patterns in a social memory paradigm. Amygdala volume was determined from manual traces of structural MRIs and fixation patterns were assessed using eyetracking methodology. A significant positive relationship was found between amygdala volume and fixation on both the face and the eye region. Amygdala volume was also found to relate to habituation across multiple presentations of different photographs of the same individual monkeys indicating a role in social memory. These data provide an important linkage between structural variation of amygdala and previous demonstrations of function in a nonhuman primate model.

Highlights

► The size of the amygdala was significantly correlated with eye contact in rhesus monkeys. ► The size of the amygdala predicted memory formation for specific individuals. ► Amygdala was more strongly related to time looking in the eyes than the face.

Section snippets

Acknowledgements

The work presented here was supported entirely by the intramural research program of the National Institutes of Health, NIMH. The authors wish to acknowledge the technical assistance and training in amygdala tracing provided by Julia Scott at the University of California – Davis. We also are indebted to the veterinary and animal care staff of the NIH animal facility in Poolesville and all of the staff at the NIMH primate core.

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