title: Combined unilateral lesions of the amygdala and orbital prefrontal cortex impair affective processing in rhesus monkeys.
abstract: The amygdala and orbital prefrontal cortex (PFo) interact as part of a system for affective processing. To assess whether there is a hemispheric functional specialization for the processing of emotion or reward or both in nonhuman primates, rhesus monkeys (Macaca mulatta) with combined lesions of the amygdala and PFo in one hemisphere, either left or right, were compared with unoperated controls on a battery of tasks that tax affective processing, including two tasks that tax reward processing and two that assess emotional reactions. Although the two operated groups did not differ from each other, monkeys with unilateral lesions, left and right, showed altered reward-processing abilities as evidenced by attenuated reinforcer devaluation effects and an impairment in object reversal learning relative to controls. In addition, both operated groups showed blunted emotional reactions to a rubber snake. By contrast, monkeys with unilateral lesions did not differ from controls in their responses to an unfamiliar human (human "intruder"). Although the results provide no support for a hemispheric specialization of function, they yield the novel finding that unilateral lesions of the amygdala-orbitofrontal cortical circuit in monkeys are sufficient to significantly disrupt affective processing.
authors.affiliation: Section on the Neurobiology of Learning and Memory, Laboratory of Neuropsychology, National Institute of Mental Health, Bethesda, Maryland 20892, USA. alicia@ln.nimh.nih.gov
authors.forename: Alicia
authors.initials: A
authors.lastname: Izquierdo
authors.forename: Elisabeth A
authors.initials: EA
authors.lastname: Murray
mesh_terms: D000339:Affect / Q000502:physiology*; D000679:Amygdala / Q000502:physiology*; D000818:Animals; D004193:Discrimination Learning / Q000502:physiology; D004435:Eating / Q000502:physiology; D004644:Emotions / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D005149:Facial Expression; D005239:Fear / Q000502:physiology; D005518:Food Preferences / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology; D007051:Ibotenic Acid / Q000633:toxicity; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging; D008297:Male; D009068:Movement / Q000502:physiology; D017397:Prefrontal Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D012054:Reinforcement, Psychology; D012193:Reversal Learning / Q000502:physiology; D012527:Satiation / Q000502:physiology; D014796:Visual Perception / Q000502:physiology
chemical_list: D018690:Excitatory Amino Acid Agonists; D007051:Ibotenic Acid