Making waves in the brain

Researchers use lasers to induce gamma brain waves in mice


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Elizabeth Thomson
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Scientists have studied high-frequency brain waves, known as gamma oscillations, for more than 50 years, believing them crucial to consciousness, attention, learning and memory. Now, for the first time, MIT researchers and colleagues have found a way to induce these 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. 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. "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.

Gamma oscillations reflect the synchronous activity of large interconnected networks of neurons, firing together at frequencies ranging from 20 to 80 cycles per second. "These oscillations are thought to be controlled by a specific class of inhibitory cells known as fast-spiking interneurons," says Jessica Cardin, co-lead author on the study and a postdoctoral fellow at MIT's McGovern Institute for Brain Research. "But until now, a direct test of this idea was not possible."

To determine which neurons are responsible for driving the oscillations, the researchers used a protein called channelrhodopsin-2 (ChR2), which can sensitize neurons to light. "By combining several genetic tricks, we were able to express ChR2 in different classes of neurons, allowing us to manipulate their activity with precise timing via a laser and an optical fiber over the brain," explains co-lead author Marie Carlén, a postdoctoral fellow at the Picower Institute.

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.

The authors further showed that these brain rhythms regulate the processing of sensory signals. They found that the brain's response to a tactile stimulus was greater or smaller depending on exactly where the stimulus occurred within the oscillation cycle. "It supports the idea that these synchronous oscillations are important for controlling how we perceive stimuli," says Moore. "Gamma rhythms might serve to make a sound louder, or a visual input brighter, all based on how these patterns regulate brain circuits."

Because this new approach required a merger of expertise from neuroscience and molecular genetics, three different laboratories contributed to its completion. In addition to Tsai, Moore and Carlén of MIT, co-authors include Jessica Cardin, research affiliate at the McGovern Institute and the University of Pennsylvania, and Karl Deisseroth and Feng Zhang at Stanford University. Other co-authors were Konstantinos Meletis, a postdoctoral fellow at the Picower Institute, and Ulf Knoblich, a graduate student in MIT's Department of Brain and Cognitive Sciences.

This work was supported by NARSAD, the National Institutes of Health, the National Science Foundation, the Thomas F. Peterson fund, the Simons Foundation Autism Research Initiative and the Knut and Alice Wallenberg Foundation.


Topics: Genetics, Neuroscience

Comments

Hi Guys, I want to discuss this research. You have to know that the combination between emission and the brain is great power. I doubt it on the sentence that you will use such knowledge with a good content. I'm searching google on the experiments you could do with mice in labyrinths beaming in with this radio-emission, and look how they behave with there consious to the artificial world of the labyrinth. It got something to do with how a human controls his self in an artifial world of government infrastructure. Yes, I'm one of the few who believe in Mind control, the autority of the brain of human via radio-emission. It is good possible, and could be created with the experiments you guys do. It is easy to say you guys use this technology in a good way, to treath people with schyzophrenia, because you could it either way use for mind control, and don't tell it. For mind control you need four components of science: Physics, to program radio-emission. Computer science, to program emission via a computer. Neuroscience, to know how the electromagnetism proces of the polar system of positive and negative forcefield in the brain work. This causes a subconsious realty who leads to the programmed behavior of people. And then you need knowledge of chemistry, to know how the chemical reactions in the brain work, and the reaction with the inner processes in the the brain and the programmed radio-emission. As said, mind control got nothing to do with voices in the head, but is programming of the behavior, via subconsious computerized programming of the biochemistry of the mind. It is not so far away, and it would lead to immense possibilatys to control society. Many things about mind control on google are a fraud. It is propaganda, which is everytime far away of the science reality. It is a simple scam to let people think it is impossible. They don't use science terms, they don't use mathematics, it is cheam information, about losers who are saying that it is all a great conspiracy, and then tell nothing reasonable about these four components of science I just mentioned. Real science is hidden for the public. I got to say that your article could have something to do with real science, with this two consequences: first, nobody looks and comments, it seems boring, and two: when they will read it they automatic believe that you guys use it for the good intention. I don't believe in it. I will go further with my searching, if you want to comment, friend me wit facebook, maybe we could sort out some data, I have a great theory.

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