“…Whereas near-infrared transmission spectropho tometry of cortical cyt aa3 has been applied to un anesthetized animals and humans (Piantadosi and Jobsis-Vander Vliet, 1984;Brazy et aI., 1985;Jobsis-Vander Vliet, 1985), reflectance spectropho tometry in the visible light spectrum (Mitnick and Jobsis, 1976;Rosenthal et aI., 1976;Jobsis et aI., 1977;Piantadosi and Jobsis-Vander Vliet, 1984) and NADH fluorometry (Chance et aI., 1962;Rosenthal and Jobsis, 1971;Vern et aI., 1981;Dora, 1984), methods with greater spatial resolution, have been mostly utilized in anesthetized preparations. While changes in the redox state of cortical cyt aa3 and NADH are usually similar following cortical activa tion (Rosenthal and J obsis, 1971;J obsis et aI., 1977;Vern et aI., 1979;LaManna et aI., 1981;Piantadosi and Jobsis-Vander Vliet, 1984), some reported dis crepancies (Dora, 1984;Dora et aI., 1984) suggest that experimental conditions, especially the use and selection of anesthesia, may influence the obtained results, e.g., pentobarbital (Rosenthal and La Manna, 1975;Marcus et aI., 1976) versus chlo ralose (Winters and Spooner, 1966;Dora et aI., 1984). In this study, attention was focused on changes in the cortical cyt aa3 redox state and blood volume during waking, slow-wave sleep, and rapid eye movement (REM) sleep.…”