Seasonal biology

The season in which a baby is born may profoundly affect the biological clock, neurological disorders and personality. A new study published by the journal Nature Neuroscience provides some evidence for seasonal
imprinting of biological clocks. The study was conducted at Vanderbilt
University.

The imprinting effect, studied on laboratory mice, may explain to some extent why babies born in winter have a higher susceptibility for winter depression, bipolar depression and schizophrenia. “Our biological clocks
measure the day length an change our behavior according to eh season. We were curious to see if light signals could shape the development of the biological clock,” said professor biological Sciences Douglas McMahon.

In their experiments, the recreated seasons using artificial light for lab mice. After the mice were weaned, they switched the light cycle. After 28 days, at which time the mice reached maturity, they remained in darkness and their behavior observed. The scientists also used gene markers to watch the activity of the master biological clocks in the mouse brains.

Biological clocks and behavior of summer born mice were stable and remained aligned with dusk. The winter born mice varied widely. “The mice born in
winter cycle show an exaggerated response to a change in season that is strikingly similar to that of human patients suffering from seasonal affective disorder,” McMahon stated.

“We know that biological clock regulates mood in humans. If an imprinting mechanism similar to the one that we found in mice operates in humans, then it could not only have an effect on a number of behavioral disorders but also have a more general effect on personality,” McMahon continued. “It’s
important to emphasize that, even though this sounds a bit like astrology, it is not: it’s seasonal biology!”

Source: Vanderbilt, ScienceDaily