Can't Sleep? Blame Your Brain Cells

Do you feel more awake and alert when the sun is shining or when it is dark and gloomy outside? Can you sleep with the lights on? Researchers at UCLA have been studying why light arouses us and have finally found some new information. They already knew that bright light arouses us and keeps us awake. It also has antidepressant effects. Darkness has the opposite effect on us. Neuroscientists have finally found the "stay awake" part of our brain. Without it, we would sleep all the time.

Jerome Siegel, a professor of psychiatry at the Semel Institute for Neuroscience and Human Behavior at UCLA, and his colleagues found the group of neurons that determines whether light excites your brain or not. In the online edition of the Journal of Neuroscience, Siegel and his colleagues reported that the cells important for a bright light arousal response can be found in the hypothalamus. The hypothalamus controls the autonomic nervous system, body temperature, hunger, thirst, fatigue, and sleep.

Siegel discovered that the cells in the hypothalamus release neurotransmitters called hypocretin. He found this by comparing mice with and without hypocretin. Siegel genetically removed the hypocretin from the mice that did not have it. Researchers examined the behaviors of the two types of mice and compared them. The mice did a lot of different activities during both light and dark phases. The study showed that the mice that didn't have hypocretin were unable to stay awake in the light, while those that had it showed a lot of activeness of certain hypothalamic cells in the light but not while they were awake in the dark.

The same UCLA research group found that the loss of hypocretin lead to narcolepsy in some cases and the sleepiness related to Parkinson's disease. But until now the neurotransmitter's role in normal behavior was not known.

This new finding helps researchers add to the already known research in humans suffering from narcolepsy. It is now thought that narcoleptics lack the arousing response to light and that both narcoleptics and Parkinson's patients have an increased chance of being depressed.

At one time, the purpose of hypocretin in rodents had examined the neuotransmitter's use during only light phases or dark phases, but not both. What made the experiments difficult was that unlike humans, mice sleep when it is light and are awake when it is dark. The researchers tested the two groups while they performed different tasks in both the light and the dark. Surprisingly, researchers found that the mice with the hypocretin removed from them were only worse at working for positive rewards during the light phase. During the dark phase, these mice learned at the same rate as the mice with hypocretin and were completely unchanged in working for the same rewards.

Siegel concluded from his findings that controlling hypocretin and increasing the use of hypocretin cells will increase the light arousal response. At the same time, blocking their function with hypocretin receptor blockers will decrease the response and lead to sleep. Both could be a new scientific breakthrough depending on whether the individual likes or dislikes being awakened by light. These findings are helping Siegel treat sleep disorders as well as depression.

What does all this have to do with you? Next time you are having trouble falling asleep, put down the cell phone, close that laptop and get some zzz's.

Here are some helpful links:
Is Light Keeping You Awake?
Brain Cells Responsible For Keeping Us Awake Identified
How Light and Darkness Govern Our Sleep Cycle

Updated December 8, 2011