Day and Night Cycle Recognized by Brain as It is Programed to Do So from Birth

Our brains are apparently programmed from birth to recognize and react to sunrise and sunset, a new research on circadian rhythms shows. Scientists at the University of Chicago say the finding may shed new light on brain development and could explain some basic human behaviors.

"This finding may show us why infants of many species eventually learn to discriminate daytime from nighttime," said Brian Prendergast, a researcher on biological rhythms and a co-author of the study.

In the experiment, hamsters grew up with one eye covered with a special contact lens to deprive it of all visual stimuli.

Although the ability to see stimuli such as movement was lost in the developing eye, the ability to determine light and dark cycles when the lens was later removed was not affected, researchers said, suggesting the pathway in the circadian system that allows the brain to synchronize with day-night rhythms in the environment is probably an innate feature of development.

"For the first time, we have established that the ability to coordinate circadian rhythms with daily changes in light exposure is not subject to very much plasticity at all - that it is not influenced by changes in the amount of light the brain receives during development," said lead author August Kampf-Lassin, an advanced graduate student at the University.

"It's interesting to see how some aspects of behavioral development are hardwired and develop into adult-typical patterns, even in the total absence of normal environmental input to the system," said Prendergast.

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The study is published in the current issue of journal PLoS One.

Source-ANI