Erik Herzog majored in biology at Duke and graduated with the intention of becoming a marine biologist. Even today he fondly recalls his work studying horseshoe crabs in Beaufort, North Carolina, under Dan Rittschof and Richard Forward of Duke. His career path changed, however, when he took particular interest in the crabs' ability to adjust their eyesight to see equally well day or night, a trait that suggested to Herzog the involvement of circadian rhythms.
Herzog and Christopher Wellins '87 (now a physician in Portland, Maine) collected crabs on the seashore by night and analyzed them by day. "They literally moved the brooms out of the closet and put us in the broom closet," says Herzog. "For a year, we worked on this project, the two of us, and on the back door we put in a picture of a beautiful Italian sunbather, whom we acknowledged in all our papers because she was our inspiration.
"We were sort of well-known in this small county, because we were the only ones with mohawks."
Now an assistant professor of biology at Washington University in St. Louis, Herzog teaches a neurophysiology lab in the fall and an undergraduate course in biological clocks in the spring. His research focuses on the suprachiasmatic nucleus (SCN), which is located in the hypothalamus, in the middle of the base of the brain. No mere gray lump, the SCN is your internal Casio, the timekeeper by which your daily biorhythms operate. By controlling the sleep cycle, it also affects metabolism, energy levels, and even the immune system.
Herzog has made headlines for his study of the relationship between brain temperature and circadian rhythm. Working with SCN cells of rats in a dish, he discovered that a change in temperature can shift the sleep cycle significantly. Since Herzog experiments on the cellular level, he doesn't concern himself with potential practical applications; nevertheless, his findings have some scientists wondering if a pill may someday be enough to circumvent let jag.
"We don't know, for example, if you have a fever, if that causes let lag," he acknowledges. "It's an interesting question to consider."
According to Herzog, the SCN seems to function by controlling more localized timekeeping apparatuses throughout the body.
"You have a clock in your SCN and it reports the central time," he explains, "but there are other clocks that exist in other areas of your brain, and even in other tissues in your body. In some ways it's like the ATM machine system that we're all used to. Those machines all have their own little clocks, but they have to synchronize to atomic time every day."
Remarkably, comparing the SCN to an atomic clock is no exaggeration. Studies have uncovered startling precision in the internal timekeeper, even when it's isolated from environmental stimuli such as sunrise or nightfall.
"I can give you, if you need one, a 23.7-hour clock," says Herzog. "It's a mouse in a cage with a running wheel, and he's accurate to less than a percent. He'll get on that wheel every day; wait 23.7 hours, and he'll get back on it again."
Herzog has also found that individual cells of the SCN can keep time on their own, although they can fall out of sync with each other if separated.
An inability of SCN cells to communicate properly with one another could lead to disarray and result in a number of sleep-cycle disorders, including insomnia.