Indiscriminate amygdala response to mothers and strangers after early maternal deprivation.

Background: In altricial species, maternal stimuli have powerful effects on amygdala development and attachment-related behaviors. In humans, maternal deprivation has been associated with both "indiscriminate friendliness" toward non-caregiving adults and altered amygdala development. We hypothesized that maternal deprivation would be associated with reduced amygdala discrimination between mothers and strangers and increased parent report of indiscriminate friendliness behaviors.

Methods: Sixty-seven youths (33 previously institutionalized; 34 comparison; age-at-scan 4-17 years) participated in a functional magnetic resonance imaging experiment designed to examine amygdala response to mother versus stranger faces. In-scanner behavior was measured. Indiscriminate friendliness was assessed with parental report.

Results: Comparison youth showed an amygdala response that clearly discriminated mother versus stranger stimuli. Previously institutionalized youths, by contrast, exhibited reduced amygdala discrimination between mothers and strangers. Reduced amygdala differentiation correlated with greater reports of indiscriminate friendliness. These effects correlated with age-at-adoption, with later adoptions being associated with reduced amygdala discrimination and more indiscriminate friendliness.

Conclusions: Our results suggest that early maternal deprivation is associated with reduced amygdala discrimination between mothers and strangers, and reduced amygdala discrimination was associated with greater reports of indiscriminate friendliness. Moreover, these effects increased with age-at-adoption. These data suggest that the amygdala, in part, is associated with indiscriminate friendliness and that there might be a dose-response relationship between institutional rearing and indiscriminate friendliness.