Sleeping patterns governed by light

The eye uses light to reset the biological clock

If you think that biological clock only reminds us to shut eye every 24 hours, you are wrong. A new study has found that it’s actually light which governs the sleeping patterns of people. Researchers at Johns Hopkins University have carried out the study and discovered that the eye uses light to reset the biological clock through a mechanism which is separate from the ability to see.

According to lead researcher Samer Hattar, the study’s findings indicate that patients with trouble sleeping or seasonal depression can benefit from development of easier, more available tests to determine if they are able to detect light properly for functions distinct from normal sight.

“It seems that even if individuals have normal sight, they might be having a malfunction that is contributing to their inability to detect light, which can adversely affect their biological clocks,” Hattar said. In their study, the researchers genetically modified laboratory mice so that a particular set of retinal ganglion cells — that receive input from rods and cones of animal’s eyes and send information to brain — no longer functioned.

The mice were still able to use light to see normally, but had great difficulty synchronizing their circadian rhythms to light or dark cycles that occurs depending on the time of the year.

Previous research in the field leads the researchers to believe that because the rodents’ internal, biological clocks are out of sync with the solar day, the animals would have difficulty learning and sleeping on a regular, 24-hour cycle. The team has not yet tested that hypothesis.

The results of the study have been published in the online edition of the Nature journal.

Via the Times

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