The season in which babies are born can have a dramatic and persistent effect on how their biological clocks function.© iStockphoto/Sean O'RiordanCrying newborn being held by doctor.
That is the conclusion of a new study published online on Dec. 5 by the journal
Nature Neuroscience. The experiment provides the first evidence for seasonal imprinting of biological clocks in mammals and was conducted by Professor of Biological Sciences Douglas McMahon, graduate student Chris Ciarleglio, post-doctoral fellow Karen Gamble and two undergraduate students at Vanderbilt University.
The imprinting effect, which was found in baby mice, may help explain the fact that people born in winter months have a higher risk of a number of neurological disorders including seasonal affective disorder (winter depression), bipolar depression and schizophrenia.
"Our biological clocks measure the day length and change our behavior according to the seasons. We were curious to see if light signals could shape the development of the biological clock," said McMahon.
In the experiment, groups of mouse pups were raised from birth to weaning in artificial winter or summer light cycles. After they were weaned, they were maintained in either the same cycle or the opposite cycle for 28 days. Once they were mature, the mice were placed in constant darkness and their activity patterns were observed.
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Here is a synopsis of the major points for 'redefining the terms of engagement':