a sleep fragmentation chamber (Lafayette Instrument, Lafayette, IN,
USA). The sweep bar moved along the bottom of the cage every 2 minutes
during the light cycle (Zeitgeber time 0–12). The sweep bar
automatically shut off and was stationary during the dark cycle
(Zeitgeber time 12–24). Control mice receiving undisturbed sleep
were placed in sleep fragmentation chambers with stationary sweep bars.
For bone marrow transplantation experiments, mice were placed in sleep
fragmentation cages 2–4 weeks after the transplant.