Adverse Rearing Experiences Enhance Responding to Both Aversive and Rewarding Stimuli in Juvenile Rhesus Monkeys

Background: While adverse rearing is thought to alter threat responding, the effects on appetitive behavior remains minimally explored. This study examines the effects that early life emotional adversity has on response to both threatening and appetitive stimuli in juvenile rhesus monkeys. Methods: Twenty-four, 2-year-old monkeys with differential rearing histories were tested for fear-potentiated startle responding and consumption of an artificially sweetened solution. Results: Relative to monkeys reared under typical conditions, monkeys removed from their mothers at birth and reared with peers demonstrated both increases in reward responding, as evidenced by greater consumption of a palatable solution in a free choice test, and increased threat responding, as evidenced by enhanced fear-potentiated startle responding. Conclusions: Findings suggest that early rearing impacts juvenile manifestations of both appetitive and aversive emotional systems. Results are discussed in the context of development, anxiety, depression, and substance abuse.