Amygdalectomy and responsiveness to novelty in rhesus monkeys (Macaca mulatta): Generality and individual consistency of effects

William A. Mason, John P. Capitanio, Christopher J. Machado, Sally P. Mendoza, David G Amaral

Research output: Contribution to journalArticle

67 Scopus citations


Rhesus monkeys (Macaca mulatta) with bilateral ibotenic acid-produced lesions of the amygdala were compared with controls in several novel situations, including exposures to metal objects, toy animals, and a person. Early in testing, the monkeys with lesions showed reduced inhibitions on responsiveness compared with controls. With continuing exposures, differences between groups diminished sharply as inhibitions waned in the controls. This outcome is consistent with the hypothesis that the amygdala mediates caution in initial reactions to ambiguous or threatening novel situations, which, in the absence of adverse consequences, diminishes with repetition. Consistency of individual responsiveness across different situations, including pairing with other monkeys, was substantial in lesioned and normal monkeys, suggesting that stable qualities of temperament influenced the results in both groups.

Original languageEnglish (US)
Pages (from-to)73-81
Number of pages9
Issue number1
StatePublished - Feb 2006


ASJC Scopus subject areas

  • Psychology(all)

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