The role of nutrition in memory formation in the honey bee, Apis mellifera

During associative learning, animals form a memory linking a stimulus, such as a sound or an odor, with a reward, such as food. We use olfactory associative conditioning in the honey bee to examine the relationship between taste, metabolic benefit and memory. Using the proboscis extension response and survival assays, we established that xylose, sorbitol and mannitol are nutritional, but tasteless sugars. Bees fed xylose or sorbitol during olfactory conditioning formed stable 24 h memories, whereas, bees receiving mannitol or no food showed significant reductions in memory. In a choice test where bees were able to choose between two feeders containing either a low concentration of sucrose alone or sucrose supplemented with a tasteless, but nutritional sugar; bees did not show a preference for the solution with higher nutritional value food. In addition, when bees only had access to a feeder containing one of the three sugars alone, without sucrose as a gustatory signal, bees showed mortality rates similar to those seen for water, suggesting that bees were unable to determine that the solutions were nutritious. To examine if bees can determine that positive taste does not always signal nutrition, we will examine memory acquisition using a tasty, but non-caloric reward. Three sugars, fucose, galactose and arabinose, are being analyzed to determine if they have appetitive taste, but no nutritional value. These results suggest that while nutrition is required to support 24 h memory formation, bees may not be able to assess nutritional content independently from taste.