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Neuroscience For Kids

Waking Up to the Light
November 24, 2011
By Sutapa Ray, Ph.D., Neuroscience for Kids Guest Writer

Do you find it difficult to fall asleep in bright sunlight and difficult to stay awake in a dark room? We tend to be awake, alert and perky when it's bright outside. Now scientists have discovered why the brain responds in this way to light. They discovered that some nerve cells in the brain become activated in the presence of light. These cells are found in the hypothalamus, a pea sized structure in the base of the brain that controls our body clock. When activated by light, the cells release a neurotransmitter called "hypocretin."

In these new experiments, scientists created mutant mice that could not make hypocretin. These mutant mice had trouble staying awake in the light. The researchers compared these mice to a control group of mice that could make hypocretin. The light sensitive cells were very active in the control mice in the presence of light, but not in the mutant mice. When they tried to hypothalamusteach the mice new tricks for a reward, both sets of mice were able to learn just as well in the dark. But in the light, the mice without hypocretin were not motivated to learn as well as the mice with hypocretin. This may be something to keep in mind when you are studying: a bright light may help you more than just to see well.

People who suffer from a disorder called "narcolepsy" also find it hard to stay awake during the day just like the mice in the experiment. Scientists have found that people with narcolepsy are not able to make hypocretin. And now, with the help of the mouse studies, we have new ideas about how hypocretin helps people stay awake in the day and keeps them motivated to learn.

References and more information:

  1. McGregor, R., Wu, M.-F., Barber, G., Ramanathan, L. and Siegel, J.M., Highly specific role of hypocretin (Orexin) neurons: Differential activation as a function of diurnal phase, operant reinforcement versus operant avoidance and light level, J. Neurosci.,31 (43): 15455, 2011.
  2. Narcolepsy - from Neuroscience for Kids

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