[imark3000]

http://news.stanford.edu/news/2009/a...ns-040109.html

In the new study, which will also appear in an upcoming print issue of Science, the medical and engineering researchers found that by far the biggest effect in "Parkinsonian" rodents occurs not by stimulating cells in the subthalamic nucleus, but by stimulating the neural wires, called axons, that connect directly to it from areas closer to the surface of the brain

"Pointing to these axons that converge on the region opens the door to targeting the source of those axons. This insight leads to deeper understanding of the circuit and could lead to new kinds of treatments," said senior author Karl Deisseroth, MD, PhD, associate professor of bioengineering and of psychiatry and behavioral sciences. "Because these axons are coming from areas closer to the brain's surface, new treatments could perhaps be less invasive than deep-brain stimulation."

To perform the research, Deisseroth's team, which included students and faculty from bioengineering, neuroscience and neurosurgery, used a technique his lab has pioneered called "optogenetics." They genetically engineered specific types of cells, or neurons, in the subthalamic nucleus regions of different rodents to become controllable with light. A blue-colored laser pulse makes the neurons more active, while a yellow laser light suppresses activity.

In a separate paper published in Nature on March 18, Deisseroth and another cadre from within his research group show that the optogenetic technique can be applied not only to the electrical behavior of neurons, but also to the much broader biochemical activity of other cell types in the body.

In his study relating to Parkinson's disease, Deisseroth used this technology to separate the different circuit elements by placing them under optical control. "It allowed us to systematically move through the circuit, turning on or off different elements and finding out which modifications of the circuit corrected the symptoms," he said.

This result also required a complementary method invented in Deisseroth's lab, namely delivering light via a thin, flexible fiber-optic cable deep into the mice brains, so that they can move and behave freely during the experiment.