ASYMMETRIC FRONTAL BRAIN ACTIVITY, CORTISOL, AND BEHAVIOR ASSOCIATED WITH FEARFUL TEMPERAMENT IN RHESUS-MONKEYS

The authors examined the hypothesis that rhesus monkeys with extreme r ight frontal electroencephalographic activity would have higher cortis ol levels and would be more fearful compared with monkeys with extreme left frontal activity. The authors first showed that individual diffe rences in asymmetric frontal electrical activity are a stable characte ristic. Next, the authors demonstrated that relative right asymmetric frontal activity and cortisol levels are correlated in animals 1 year of age. Additionally, extreme right frontal animals heel elevated cort isol concentrations and more intense defensive responses. At 3 years o f age, extreme right frontal animals continued to have elevated cortis ol concentrations. These findings demonstrate important relations amon g extreme asymmetric frontal electrical activity, cortisol levels, and trait-like fear-related behaviors in young rhesus monkeys.