Experience-dependent asymmetric variation in primate prefrontal morphology.

Theories of human development suggest that experiences embedded in social relationships alter prefrontal brain systems that mediate emotional self-regulation. This study tests for experience-dependent effects on prefrontal gray and white matter volumes determined in 39 young adult monkeys (Saimiri sciureus) 4 years after conditions that modified early maternal availability. These conditions were previously shown to alter subsequent measures of emotional behavior, social propensities, and hypothalamic-pituitary-adrenal axis stress physiology. Here we identify significant differences in right but not left adult prefrontal volumes, with experience-dependent asymmetric variation most clearly expressed in ventral medial cortex measured in vivo by magnetic resonance imaging (MRI). Follow-up studies now need to determine whether maternal availability directly affects or interacts with subsequent experiences to alter prefrontal substrates of emotional processing and sensitivity to stress.