Cool hamsters get sleepy

The relationship between sleep and natural hypothermic states, like daily torpor and hibernation, has always been of interest for sleep researchers. The three states were long considered functionally homologous. However, while investigating the effects of daily torpor on sleep in the Djungarian hamster (Phodopus sungorus), the results suggested that the animals are sleep deprived during hypothermia, and can only recover this sleep debt after return to euthermia. The data indicate that an important function of sleep cannot be fulfilled during the torpid state, a finding which may give additional insights into the processes involved in sleep regulation.