Letters to the Editor are an interesting feature of peer-reviewed scientific journals. The function of this section varies from journal to journal, but, in general, this is where you'll find things like critiques of research published in previous issues, and short write-ups on findings that don't yet warrant their own big, formal research paper. Neuroscience blogger Vaughan Bell found a neat example of the latter in an old 1993 issue of the American Journal of Psychiatry.

Dr. Harold W. Koenigsberg and his colleagues were in the process of studying the causes of panic and anxiety disorders, in hopes of better understanding why some people are prone to panic attacks and others aren't. Part of that research involved determining whether you could have a panic attack while sleeping. They wanted to see whether a panic attack could still happen if the patient wasn't actively thinking about the causes of the panic attack, like they might when awake. Basically, Koenigsberg was trying to figure out how much of a panic attack was attributable to chemistry changes, and how much was related to cognitive processing.

Koenigsberg and company injected sleeping patients with caffeine, to produce the physical symptoms of panic. And that's when they noticed something odd. Two of the patients reported olfactory hallucinations—they smelled things that weren't there. Here's what Koenigsberg wrote in his Letter to the Editor:

Mr. A, a 38-year-old man with no personal or family history of psychiatric disorders, received an intravenous dose of 250 mg of caffeine, delivered as a bolus over a 60-second period during an episode of stage 3-4 sleep. Fourteen minutes after receiving the caffeine, he awakened and reported an "interesting smell or taste-more like a smell."

Ms. B, a 34-year-old woman with a generalized anxiety disorder, awakened experiencing a smell like that of "plastic or burnt coffee" 3 minutes after receiving a 250 mg bolus of caffeine during a period of stage 3-4 sleep.

Previous research by other people had found that hallucinations like this could happen, but the hypothesis had been that the hallucinations were related to seizures. Koenigsberg's patients had no history of seizures, and they hadn't shown any signs of experiencing seizures when they had their hallucinations.

So Koenigsberg offered a new hypothesis: We know caffeine can work as a taste enhancer. So, maybe, the intravenous caffeine was either causing people to pick up smells and tastes that were normally undetectable, or the caffeine was prompting sensory systems to trick themselves, finding "smells" where none actually existed.

And this is why Letters to the Editor are so nifty. Koenigsberg later published on his panic attack study, but the biochemical function of caffeine on the human sensory system wasn't something he was much interested in. Letters to the Editor allowed him to share a weird finding, which might otherwise have been shoved into a drawer, never to be heard from again.

Instead of being lost, Koenigsberg's finding on caffeine-induced hallucinations went on to influence at least four other studies, including one on migraine hallucinations published last month.

Image: Caffeine fix, a Creative Commons Attribution (2.0)image from davemorris's photostream