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a) Total Sleep Time (TST) during each day (E1-E7) of increased sleep opportunity, and during the 12-hour nighttime and the 4-hour daytime sleep opportunity within each day. b) TST, Rapid-Eye Movement (REM) sleep and non-REM (NREM) sleep during the baseline sleep episode (Day BL, shaded area) and during days E1-E7 for older (filled symbols) and younger (open symbols) subjects. The data are plotted as mean and standard errors estimated by the fitted exponential function.
