I know what the science says - that caffeine is not proven to enhance my mental performance - but I swear by my morning cup of Joe. A new study seems to back this up. It joins a growing, albeit short, list of experiments showing caffeine may heighten brain function.

In this study, caffeine was shown to affect an area deep in the brain that is responsible for facilitating memory. Caffeine is able to alter brain chemistry because the molecule is small enough to enter the brain, after which it interrupts a process behind sleepiness.

We get sleepy as the day wears on, because a brain chemical called adenosine builds up. This neurotransmitter stops the brain from overworking by binding with nerve cells to slow them down. This makes a person sleepy, and when they sleep, adenosine levels drop, resetting the sleep clock. But caffeine interrupts this cycle by competing with adenosine. Since caffeine is structurally similar, it can also bind to nerve cells, blocking adenosine and stopping the sleep signal. Rather than slow down, the neurons keep going.

In the new study, researchers gave rats the caffeine equivalent of two cups of coffee, which is small compared with the massive doses in other studies. They then measured the electrical signals of neurons in the hippocampus, an area of the brain just behind the ears. In particular, they measured a part of the hippocampus called CA2. The cells there responded with a huge burst of electrical activity. The higher the dose of caffeine, the greater the response.

If human CA2 neurons respond similarly, this area of the brain may be the most sensitive to caffeine. The results suggest caffeine may temporarily stimulate mental sharpness and learning, which makes sense because the hippocampus is responsible for organizing memory and developing spatial memory.

None of this is conclusive yet, but if it's true, that's one habit we can keep - guilt-free!