In addition, their experiments found that the imprinting of clock gene activity near birth had dramatic effects on the reaction of the biological clock to changes in season later in life. The biological clocks and behavior of summer-born mice remain stable and aligned with the time of dusk while that of the winter-born mice varied widely when they were placed in a summer light cycle.
"The mice raised in the 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 commented.
Exactly when the imprinting occurs during the three-week period leading up to weaning and whether the effect is temporary or permanent are questions the scientists intend to address in future experiments.
Seasonality and Personality
The new study raises an intriguing but highly speculative possibility: seasonal variations in the day/night cycle that individuals experience as their brains are developing may affect their personality.
"We know that the 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," said McMahon.
"It's important to emphasize that, even though this sounds a bit like astrology, it is not: it's seasonal biology!" McMahon added.
Mice in this study were raised on artificial seasonal light cycles in the laboratory and the study was repeated at different times of the year. In humans, studies conducted in the northern and southern hemispheres have confirmed that it's the season of winter not the birth month that leads to increased risk of schizophrenia. There are many possible seasonal signals that could affect brain development, including exposure to flu vi
|Contact: David F. Salisbury|