Fig. 1.

Wheel-running activity records of representative hamsters. Each line represents 24 hr plotted in 10 min bins fromleft to right. Vertical deflections on the line indicate time bins in which wheel-running activity occurred. Shading represents lights-off (LD 14:10). A, Control test, with constant dark beginning 6 hr before usual dark onset and no behavioral disturbance. A 38 min phase advance was evident on the second day after the procedure, relative to the average time of activity onset in LD before the first day of constant dark. B, 1 hr sleep deprivation (shaded rectangle) that induced a 180 min phase advance. C, 3 hr deprivation that induced a 165 min advance. D, 3 hr sleep deprivation with the home cage wheel locked for 6 hr, which induced a 190 min phase advance.