Lasers 'make waves' in the brain

April 28, 2009--For more than 50 years, scientists have studied high-frequency brain waves known as gamma oscillations, believing them crucial to consciousness, attention, learning, and memory. For the first time, Massachusetts Institute of Technology (MIT; Cambridge, MA) researchers and colleagues have found a way to induce gamma waves by shining laser light directly onto the brains of mice.

Apr 28th, 2009

April 28, 2009--For more than 50 years, scientists have studied high-frequency brain waves known as gamma oscillations, believing them crucial to consciousness, attention, learning, and memory. For the first time, Massachusetts Institute of Technology (MIT; Cambridge, MA) researchers and colleagues have found a way to induce gamma waves by shining laser light directly onto the brains of mice.

The work takes advantage of a newly developed technology known as optogenetics, which combines genetic engineering with light to manipulate the activity of individual nerve cells (see related story on laser neural stimulation). The research helps explain how the brain produces gamma waves and provides new evidence of the role they play in regulating brain functions--insights that could someday lead to new treatments for a range of brain-related disorders.

"Gamma waves are known to be [disrupted] in people with schizophrenia and other psychiatric and neurological diseases," says Li-Huei Tsai, Picower Professor of Neuroscience and a Howard Hughes Medical Institute investigator at MIT. "This new tool will give us a great chance to probe the function of these circuits."

Tsai co-authored a paper about the work that appears in the April 26 online issue of Nature.

The trick for inducing gamma waves was the selective activation of the "fast-spiking" interneurons, named for their characteristic pattern of electrical activity. When these cells were driven with high-frequency laser pulses, the illuminated region of cortex started to produce gamma oscillations. "We've shown for the first time that it is possible to induce a specific brain state by activating a specific cell type," says co-author Christopher Moore, associate professor of neuroscience and an investigator in the McGovern Institute. In contrast, no gamma oscillations were induced when the fast-spiking interneurons were activated at low frequencies, or when a different class of neurons was activated.

For more information, go to www.mit.edu.

--Posted by Gail Overton, gailo@pennwell.com; www.laserfocusworld.com.

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