Stress-related sleep disorders, notably insomnia, are widely prevalent in the general population. There are few good animal models in which to study the mechanisms underlying insomnia or the sleep abnormalities associated with psychiatric disorders. Dr. Ned Kalin has been studying the role of the amygdala in emotional processing in the rhesus monkey, a relevant model for human emotion and psychopathology. In collaboration with Dr. Kalin, the Principal Investigator has obtained preliminary data from rhesus monkeys with amygdala lesions which suggest that the amygdala mediates stress effects on sleep and may be important in organizing REM/NREM sleep cycles as well. In this revised proposal, the Principal Investigator plans to study rhesus monkeys with total, bilateral lesions of the amygdala, and bilateral lesions of the central nucleus of the amygdala, the major output site from the amygdala. Using telemetry, she will compare sleep patterns under normal, unrestrained conditions and in response to a variety of stressors. These studies will establish the role of the amygdala in normal sleep organization as well as in response to emotional and physical stressors. Results obtained from these studies should increase our understanding of the mechanisms underlying sleep abnormalities in psychiatric disorders and insomnia.