In a new study of rat brains published in Nature Neuroscience, researchers report that a single dose of caffeine strengthens brain cell connections and causes a surge in electrical currents in a region of the brain called the “hippocampus.” The hippocampus is in part responsible for spatial memory and the way our minds change short-term memories into long-term memories. Previous studies conducted to measure the effects of caffeine on the hippocampus have used caffeine doses that were much larger than those found in a cup of coffee, noted Serena Dudek, Ph.D., of the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., one of the coauthors of the study. In contrast, Dudek explained, she and her teammates examined the effects of relatively modest doses of caffeine on a small region of the hippocampus.
After giving rats the equivalent of two filter-drip cups of coffee (two milligrams of caffeine/kilogram of body weight), the researchers conducted a test to see how strong nerve cells’ electrical messages in the brain tissue of the CA2 area of the hippocampus brain became.
When the nerve cells dosed with caffeine were stimulated, the area’s electrical activity increased as compared with the electrical activity observed in stimulated cells without caffeine exposure. The bigger the caffeine dose, the more the electrical activity increased. A caffeine dose ten times higher – a dose that only extreme coffee drinkers reach – provoked the biggest response in the nerve cells in the CA2 area.
The scientists noted similar effects when, instead of having rats consume the caffeine, they applied caffeine directly to CA2 nerve cells in a dish, a result that ruled out effects from post-caffeine changes in blood flow.
These heightened nerve connections in the hippocampus could play a role in learning and memory, because, as stated above, the primary responsibilities of the hippocampus include creating spatial memories and converting short term-memories into long-term memories. An example of this phenomenon is that cab drivers in London, who have to navigate London’s labyrinthine roads, and thus require an astonishingly complex and comprehensive spatial understanding, have larger hippocampi than average people.
Increasing the understanding of caffeine’s effect on the brain in this and other respects could enable scientists to increase its already powerful benefits. (See post, “Caffeine: Unexplored Source of Pharmacological Treasures.”)