Researchers in Nashville have found that the season in which mice are born can dramatically affect how their body clocks work in later life. Mice born in the summertime were better at adapting their body clocks to night/day changes than those born in the winter.
Publishing this week in Nature Neuroscience, Douglas McMahon and colleagues reared mice in artificially-engineered seasons. Some were raised with more 'daylight', emulating summer and some were exposed to more night time as they grew up.
Another sub-section of the mice were then exposed to a different 'season' during adolescence and finally, once they reached adulthood, all of the mice were put into darkness so that the researchers could observe how they scheduled their activities.
The winter mice in this environment slowed all their activities whereas the summer mice maintained a regular day-night cycle. So the researchers think that the circadian rhythm is actually imprinted on the brain during a key period in the mouse's development.
They also say that a "strikingly similar response" is present in people who suffer from SAD - seasonal affective disorder. The next step will be to find out exactly when this seasonal imprinting occurs.
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