To assess plasma levels of corticotropin and cortisol, 4 mL of blood were collected at each point in a heparinized tube that was placed on ice immediately after blood drawing. Within 30 minutes of collection, the blood was centrifuged at 4°C and the plasma was pooled and aliquoted for corticotropin and cortisol assays. All tubes were stored at −70°C and express shipped to Kreek Laboratories, Rockefeller University. Assay processing was conducted using standard radioimmunoassay procedures at Kreek Laboratories under the supervision of one of us (M.J.K). Laboratory responses were assessed at baseline prior to imagery (8:40 and 8:55 am representing times −20 and −5) and immediately following imagery (time 0) and at repeated recovery points every 15 minutes (15, 30, 45, 60, and 75 minutes) after imagery. Because cortisol secretion from the adrenal glands occurs in response to circulating corticotropin released from the pituitary and may vary under rest and challenge conditions,25-27 we also assessed adrenal sensitivity as a ratio of cortisol to corticotropin. Furthermore, previous research on conditions with known HPA axis disturbances (eg, rheumatoid arthritis and posttraumatic stress
