Imaging brain activity of honey bees sensing odors while they sleep

Understanding the functions of sleep and dreaming requires that we understand how the brain processes sensory information. Do we replay and consolidate memories during sleep? When insects sleep, do they process sensory information in a manner similar to their processing of sensory information while awake? European honey bees (Apis mellifera), when awake, process odor information in the antennal lobe and in higher brain regions. Odors elicit an odor-specific, combinatorial activation pattern. We hypothesize that bees sense odors during sleep, and we address the question of how odors are represented at the level of the antennal lobe when bees are asleep. We measured behavior and neuronal activity in response to odor in seven honey bees’ antennal lobes, using calcium imaging while the honey bees were awake and asleep. To our knowledge, this is the first calcium imaging of a sleeping invertebrate, and the first application of human brain imaging techniques to an invertebrate. We believe that imaging a sleeping brain in an insect that is an exceptionally capable learner will pave the path for future investigations of the value of sleep in the context of memory consolidation and learning, and open investigations as to the importance of sleep in insects.