In REM sleep deprivation studies, the disk will be rotated for REM sleep only. The experimental rat has a yoked control in the adjacent cage. Whenever the experimental rat starts to sleep the disk is rotated and forces both rats to wake up and walk in the opposite direction. Thus both rats receive the same physical stimulation but that is targeted to awaken the sleeping experimental rat. Additionally, most immersions of yoked and experimental are partial but later on in deprivation rats would enter the water fully or when they failed to wake up or were unable to walk seemingly because of weakness.
Some studies also use an immersion control.
The frequency and duration of partial immersion and full immersion is determined in the experimental rat. Immersion control rats are then maintained on similar disks that could be lowered into the pan. These rats are automatically immersed to match the frequency of immersion in the experimental animals. Duration of Sleep Deprivation Studies Most sleep deprivation studies last many days. For example, performance is frequently impaired in the form of lapses which may be the intrusion of incipient sleep processes.