Neural correlates of maternal separation in Rhesus monkeys

Background: The neurobiological basis of stress and anxiety in primates rem ains poorly understood. In this study, we examined the neural response to a naturalistic social stressor: maternal separation. We used rhesus monkeys as an animal model because of their close phylogenetic affinity with humans . Methods: Six juvenile rhesus monkeys received [F-18]-fluorodeoxyglucose pos itron emission tomography scans following I) a period together with their m others and again after separation from their mothers 2) with or 3) without visual contact. Image subtraction revealed brain regions that exhibited alt ered activity during separation. In addition, plasma cortisol concentration s obtained following each condition were tested for correlations with regio nal brain activity. Results: Maternal separation activated the right dorsolateral prefrontal co rtex and the right ventral temporal/occipital lobe. There was also decrease d activity in left dorsolateral prefrontal cortex associated with separatio n stress. Correlational analyses demonstrated these activated and deactivat ed regions to be positively and negatively correlated with cortisol, respec tively. Additionally, correlational analyses revealed cortisol-related acti vation in brainstem areas previously implicated in stress and anxiety. Conclusions: In juvenile rhesus monkeys, the stress of maternal separation is associated with activation in the right dorsolateral prefrontal cortex a nd ventral temporal/occipital lobes and decreased activity in the left dors olateral prefrontal cortex. (C) 2001 Society of Biological Psychiatry.