Mouse vision has a rhythm all its own( In the eyes of mammals visual inform...),Health

In the eyes of mammals, visual information is processed on a daily schedule set within the eyes themselvesnot one dictated by the brain, according to a new report in the August 24 issue of the journal Cell, a publication of Cell Press. The researchers found in mice that the eyes normal rhythmic response to light requires only that a molecular "clock" inside the retina go on ticking. The retina is a layer of nerve tissue covering the back of the eyeball, which is often likened to the film in a camera; without it, images can't be captured.

The results offer the first glimpse into the physiological importance of circadian clocks found in organs throughout the body, said Charles Weitz of Harvard Medical School. The retina's apparent independence when it comes to keeping itself on time further challenges the notion that the circadian rhythms of the bodywhich drive regular patterns of physiology and behaviorstrictly follow orders handed down from a "master clock" in the brain, the researchers said.

"We're moving from a dictatorial model of the circadian system to a federal model," Weitz said. He added, however, that the brain's master clock isnt "completely off its pedestal" yet as it might still play a lead role in synchronizing the clocks found in other organs.

It has long been known that the roughly 24 hour circadian clock controlling behavior in mammals is located in the brains suprachiasmatic nucleus (SCN), Weitz explained. Even when animals are placed under conditions of constant darkness, that daily rhythm marches on.

More recently, researchers have discovered that circadian clocks are also distributed in other mammalian tissues, including the retina, multiple brain regions, and many peripheral tissues such as the liver and kidneys. But while scientists had suspected physiological functions for those many timepieces, few studies had addressed the issue.

In the new study, the researchers found that retinas of mice th
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