Elsevier

Neuroscience

Volume 106, Issue 4, 31 October 2001, Pages 653-658
Neuroscience

Letter to Neuroscience
Increased social fear and decreased fear of objects in monkeys with neonatal amygdala lesions

https://doi.org/10.1016/S0306-4522(01)00445-6Get rights and content

Abstract

The amygdala has been implicated in the mediation of emotional and species-specific social behavior (Kling et al., 1970, Kling and Brothers, 1992, Kluver and Bucy, 1939, Rosvold et al., 1954). Humans with bilateral amygdala damage are impaired in judging negative emotion in facial expressions and making accurate judgements of trustworthiness (Adolphs et al., 1998, Adolphs et al., 1994). Amygdala dysfunction has also been implicated in human disorders ranging from social anxiety (Birbaumer et al., 1998) to depression (Drevets, 2000) to autism (Bachevalier, 1994, Baron-Cohen et al., 2000, Bauman and Kemper, 1993). We produced selective amygdala lesions in 2-week-old macaque monkeys who were returned to their mothers for rearing. At 6–8 months of age, the lesioned animals demonstrated less fear of novel objects such as rubber snakes than age-matched controls. However, they displayed substantially more fear behavior than controls during dyadic social interactions. These results suggest that neonatal amygdala lesions dissociate a system that mediates social fear from one that mediates fear of inanimate objects. Furthermore, much of the age-appropriate repertoire of social behavior was present in amygdala-lesioned infants indicating that these lesions do not produce autistic-like behavior in monkeys. Finally, amygdala lesions early in development have different effects on social behavior than lesions produced in adulthood.

Section snippets

Subjects and living conditions

Six infant rhesus monkeys (Macaca mulatta) were used in this study. Three infants (two males, one female) received bilateral amygdala lesions at 14 days (±2 days) after birth, while the other three infants (two males, one female) served as controls. Infants were housed with their mothers in standard home cages (61 cm W×66 cm D×81 cm H) until they were on average 5.5 months old, when the mothers were removed. Following weaning, the infants remained in their home cage and were allowed access to

Acknowledgements

This research was supported, in part, by grants from the National Institute of Mental Health and by the base grant of the California Regional Primate Research Center. This work was also supported through the Early Experience and Brain Development Network of the Macarthur Foundation. We thank Greg Vicino and the veterinary staff of the CRPRC for excellent care of the animal subjects. We also thank Jeffery Bennett, Sarah Cox and Pamela Tennant for assistance with surgical and histological

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