Caffeine Increases Memory for Humans and Honeybees
Consumption of caffeine, in moderation, is reported to have a number of health benefits including increases in alertness, stamina during exercise, pain relief, and memory. Further research indicates that chemically, it functions as an antioxidant and consequently helps to minimize damaging free radicals that are present in a variety of oxidative stress-related disorders including Alzheimer’s Disease and heart disease. Additional data suggest that caffeine may play a role in minimizing depression by increasing the production of dopamine in the brain.
In a recent publication in the journal Science, Dr. Geraldine Wright and colleagues examine the role of caffeine in enhancing memory by exploring an ecological role for low concentrations of caffeine in floral nectar and pollen. They hypothesized that the presence of caffeine may be important in keeping pollinators returning to the plant.
In many cases, pollination is a mutually beneficial process for both pollinators and plants. Hence, from an ecological and evolutionary perspective, plants have evolved to find ways to make their nectar both more memorable and more desirable. In some cases this may involve an increase in nectar strength or quality. In the case of select species’ in the Citrus and Coffea genera however, it seems this has involved the inclusion of caffeine in the nectar.
The researchers trained honeybees to associate a floral scent with a 0.7M sucrose solution containing a variety of different concentrations of caffeine. The data indicate that those honeybees that consumed nectar with low levels of caffeine were 3 times more likely to remember the conditioned scent 24 hours later. Caffeine concentrations greater than 1mM resulted in honeybees being deterred from drinking the sucrose-rich reward solution. The team reported that this is likely due to the bitter taste and toxicity of caffeine at high concentrations.
A deeper exploration into the active molecular pathway in the observed caffeine effect suggests that caffeine increases the excitability of Kenyon cells, a type of cell found in arthropods including honeybees. Functionally, Kenyon cells are similar to human hippocampal neurons in that they play a role in long term memory formation. Indeed, the authors of this paper were able to effectively reverse the caffeine by blocking acetylcholine receptors on the Kenyon cells, thus minimizing their level of activation.
Together, these data corroborate previous reports indicating that low doses of caffeine result in enhanced cognitive performance and memory in humans. They further suggest that this pharmacologic role of caffeine translates to the evolution of various plant species in attracting pollinators via providing a chemical substance to increase long-term memory of honeybees.
Chittka L, & Peng F (2013). Neuroscience. Caffeine boosts bees’ memories. Science (New York, N.Y.), 339 (6124), 1157-9 PMID: 23471393
Wright, G., Baker, D., Palmer, M., Stabler, D., Mustard, J., Power, E., Borland, A., & Stevenson, P. (2013). Caffeine in Floral Nectar Enhances a Pollinator’s Memory of Reward Science, 339 (6124), 1202-1204 DOI: 10.1126/science.1228806
WebMD, New clues on caffeine’s health benefits, (2011, May 6).