Fig. 5.
Sleep in bees benefits extinction of the classical conditioned proboscis extension response, but not classical conditioning of the response itself. On day 1 bees were conditioned on three trials (×3) in which an odor (conditioned stimulus, CS) was shortly followed by the presentation of a toothpick with sugar solution (unconditioned stimulus, US). During the subsequent night, one group of bees was sleep deprived (SD) for 16 h by gentle vibration on a vortex machine every 5 min whereas the other group had undisturbed rest. On the following day animals were tested on two trials (×2) only including the presentation of odor. There was no difference in the proboscis extension response between the two groups. The two test trials simultaneously served as extinction trials, as odor presentation was not rewarded by sucrose. Animals of the original sleep group were then divided into a sleep deprivation group which was deprived from sleep the following night and a sleep group which had undisturbed rest on this night. When re-tested on the subsequent day, the bees of the sleep deprivation condition persisted to respond to the odor, whereas the sleep group successfully suppressed the proboscis extension response. **p < 0.01, n.s., not significant, for comparisons between groups. Data from Hussaini et al. (2009).