By Medical Discovery News

May 19, 2012

During the morning rush or the afternoon lull, Americans all seem to reach for a pick-me-up using the same thing – caffeine, whether it be coffee, soda or tea. The human love affair with caffeine dates back 500,000 years when Paleolithic man drank tea. While people today use caffeine as a stimulant, experiments have not been able to prove it actually improves cognitive performance, meaning it doesn’t help someone memorize or retain facts for an upcoming exam.

That hasn’t stopped scientists from studying caffeine to understand its effects on the brain. Now, a new report joins a short list of studies showing a shot of Red Bull could enhance mental acuity.  Serena Dudek of the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., is co-author of the study. In experiments with rats, her team found caffeine jolts neurons in an area deep inside the brain responsible for forming, organizing and storing memory.

Caffeine alters brain chemistry because the molecule is small enough to enter the brain and interrupt normal nerve cell functions. In particular, it interferes with a process responsible for sleepiness. People get sleepy because as the day wears on, a chemical in the brain called adenosine builds up. This neurotransmitter protects the brain and keeps it from overworking by binding with nerve cells to slow their activity. As neurons slow down, a person gets sleepy; however, as they sleep, adenosine levels drop, which resets the sleep clock.

Caffeine interrupts this cycle by competing with adenosine for binding to nerve cells. Since caffeine is structurally similar, it can bind to nerve cells, blocking adenosine and stopping the sleep signal. Rather than slow down, the neurons keep working and, in Dudek’s study, they do so in an area of the brain not seen before.

When researchers gave rats the caffeine equivalent to two cups of coffee, a small amount compared with the massive doses used in other studies, they measured the electrical signals of neurons in an area of the hippocampus called CA2. The cells there responded with a huge burst of electrical activity, and the higher the dose of caffeine, the greater the response.

Scientists were able to replicate the experiment on CA2 nerve cells grown in a petri dish.  After only five minutes of exposure to caffeine, these nerve cells were still activated three hours later. If human CA2 neurons respond the same way, this area of the brain may be the most sensitive to caffeine.

The results suggest caffeine may temporarily stimulate mental sharpness and could have a role in learning, which makes sense because the hippocampus, a set of seahorse-shaped organs behind the ears, is responsible for organizing and developing memory. That’s why London cab drivers who learn incredibly complex traffic routes have an enlarged hippocampus.

The study’s results, though on rats, may give a better understanding of caffeine’s effects on the human brain. If caffeine does enhance memory, the 80 to 90 percent of Americans who swear by their daily caffeine habit have more reason to get another cup.

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