The Scientific Activist (Archives)


May 25, 2006

Like Clockwork

Afarensis points his readers to a new study that’s billed to debunk “popular belief” by demonstrating the existence of a second clock in the brain, outside of the central one in the suprachiasmatic nucleus. As Bora Zivkovic points out on his blog Circadiana, this isn’t really anything that new, and the study seems to have been over hyped in its press release.

In fact, it’s well-known that the body hosts a multitude of individual clocks that are coordinated by the suprachiasmatic nucleus. I even wrote about this topic last April in The Battalion, Texas A&M University’s student newspaper:
David Earnest, associate professor of medical neurobiology, said that if left alone, internal clocks take on their own rhythm - closer to 25 hours in humans.

Although something can be said for walking to the beat of your own drum, an incorrectly set clock can lead to a host of health problems.

Earnest said that, in addition to the central clock, mammals have local clocks operating throughout the body. The role of the central clock is to synchronize these other clocks. In fact, the undesirable symptoms of jet lag, ranging from decreased productivity to an increased risk of infection, occur when these various internal clocks do not catch up to the new time zone at the same speed.

In northern areas, many people become depressed during the exceptionally dark winters. This condition called seasonal affective disorder is often treated with phototherapy - exposing patients to high-intensity light at a regular time each day.

Interestingly, this led to a discussion on why we need these internal clocks at all, since they can cause so much trouble:
"Circadian rhythms allow preparation in advance for predictable changes in the environment," Earnest said. "(For example,) if you're an animal living in the wild and you're nocturnal, you need to have the various neurotransmitters in the brain that regulate motor activity ready to roll in advance of it becoming nighttime."

The article overall focuses more on what were then recent findings regarding how the body resets its internal clocks. The entire article can be found here, and I’d encourage you to check it out. Enjoy!


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