ABSTRACT: Sleep is known to support memory consolidation in animals, including humans. Here we ask whether consolidation of novel navigation memory in honeybees depends on sleep. Foragers were exposed to a forced navigation task in which they learned to home more efficiently from an unexpected release site by acquiring navigational memory during the successful homing flight. This task was quantified using harmonic radar tracking and applied to bees that were equipped with a radio frequency identification device (RFID). The RFID was used to record their outbound and inbound flights and continuously monitor their behavior inside the colony, including their rest during the day and sleep at night. Bees marked with the RFID behaved normally inside and outside the hive. Bees slept longer during the night following forced navigation tasks, but foraging flights of different lengths did not lead to different rest times during the day or total sleep time during the night. Sleep deprivation before the forced navigation task did not alter learning and memory acquired during the task. However, sleep deprivation during the night after forced navigation learning reduced the probability of returning successfully to the hive from the same release site. It is concluded that consolidation of novel navigation memory is facilitated by night sleep in bees.They use fancy technical words to try to distract us from their obviously evil intentions to drive honeybees crazy through sleep-deprivation but, in their defence, instead of blasting Bruce Springsteen's "Born in the USA" for hours and hours on repeat, they simply placed them on a machine that would shake the colony on a regular basis to prevent a restful sleep. So they weren't absolute monsters.
More seriously, the research is fascinating as it extends upon the research suggesting that sleep in animals is used as a mechanism for memory consolidation. Despite the presence of sleep being a common experience across many animals, the reason for sleep is still a topic of debate, with one of the leading theories is that it is a kind of defragmentation of the brain. This theory has found a great amount of evidence in humans and other mammals1 and birds2 but so far the evidence in insects has been patchy, and for the theory to hold weight it needs to find evidence in all animals that sleep - this is what this recent research attempted to do.
The research and methods were interesting but to ensure I maintain everyone's attention, here is a picture of RoboBee:
The nifty little gadget on the back of the bee tracked the path that they would take whilst learning the paths between their foraging paths and colony, and so continuing on with their sadistic methods, they would let the bees learn a way home and then see what happens when they displace them before letting them try to find a way back to the colony. In other words, the particular memory mechanism the authors were interested in is that of "relearning" and they wanted to know what happened when they had had a sleepless night.
Like most of us that have had a rough weekend or two in our past, we can expect that what happened to the bees was what happens to us on those early Monday morning starts - we're disorientated, a step behind the play, and by the time we get home we really have no idea what happened between waking up and getting home. For bees and 'relearning', what happened was that fewer than half of the bees managed to make it back home, and for those that did, they took almost twice as long to make it back compared to the bees that were refreshed and well-slept.
So what does all this research mean? That those sick bastards have added to the homelessness problem in honeybees, with a handful more of them now wandering around trying to get back to their colony. I'm sure that we can also draw conclusions about the validity of the memory consolidation theory of sleep as well, but I think we have to be careful not to allow such academic concessions detract from the need to organise a search party to find those poor lost bees.
1. Marshall, L. and Born, J. (2007). The contribution of sleep to hippocampus dependent memory consolidation. Trends in Cognitive Sciences, 11, 442-450.↩
2. Jackson, C., McCabe, B. J., Nicol, A. U., Grout, A. S., Brown, M. W. and Horn, G. (2008). Dynamics of a memory trace: effects of sleep on consolidation. Current Biology, 18, 393-400.↩