Monday, October 27, 2008

New Horizons in Science: Light Sensitive Brains

What importance does ecological diversity have in brain science? Even tiny organisms can offer unique characteristics and properties that advance the research, and no one knows where the next discovery will come from.

For example, Dr. Karl Deisseroth of Stanford can inject a light sensitive gene obtained from a specific type of one-celled algae into an animal brain and then use optical stimulation to make different circuits in the brain switch on or off. Unlike electrical stimulation, this optical stimulation can be targeted to a very specific neuron. This is especially important in the hypothalamus, where the neurons linked to very different but important activities intermingle. This is also the area of the brain associated with many psychiatric diseases.

One such psychiatric problem is narcolepsy triggered by rewarding arousal - food and social contact, for instance. Deisseroth showed a very sad video of a dog trying to eat, but falling asleep by the time it started chewing. This problem is very debilitating in humans, and is caused by a deficit in certain receptors.

Deisseroth has used the light sensitive gene and optical stimulation to trigger a wake state in lab animals. He hopes that this might lead to therapy for narcolepsy, and that the method could be used to address other psychiatric diseases by targeting other specific neurons. However, he cautions that there are ethical and philosophical issues involved. If the hypothalamus is the area of the brain that tells us what we "want," how much can we change what we want? Is "want" defined only neurologically?

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