Sleep deprivation not only plays havoc with your life, but it also wrecks your memory. Ireneusz Ruczyński from the Mammal Research Institute, Poland, explains that sleep deprivation may affect our ability to consolidate memories, by transferring them from the short- to long-term memories. And, it turns out that animals that hibernate to conserve energy may suffer similar problems. ‘Both REM sleep and slow wave sleep are reduced during torpor’, say Ruczyński and Theresa Clarin from the Max Planck Institute for Ornithology, Germany, adding that animals that have recently emerged from hibernation spend a lot of time sleeping to repay the deficit. However, the jury was out about the effect of torpor and hibernation on rodent memories: some species seem to form long-term memories fine while the memories of others are impaired. Intrigued by the possibility that the low body temperature associated with torpor could impact memory formation, Ruczyński and his colleagues began testing the memories of chilled great mouse-eared bats (p. 4043).

Keeping bats at either 22°C or 7°C, Ruczyński, Clarin and Bjoern Siemers trained them to find food in a maze. Both groups of bats also had to learn the location of a dry perch when they were placed in a wet arena. Testing the animals' memories of the location of food in the maze and where the perch was in the wet arena, the team found that the bats' memories were equally good; their body temperature did not affect their ability to form memories. The team says, ‘The lack of clear cognitive effects caused by the decrease in body temperature could be explained by a bat's life history’, pointing out that bats live in complex environments and that this could have forced them to develop compensating mechanisms that ensure that their memories are sound.

T. M. A.
B. M.
Do greater mouse-eared bats experience a trade-off between energy conservation and learning?
J. Exp. Biol.