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.
Written by Deborah Halber, Picower Institute
Elizabeth Thomson | EurekAlert!
During HIV infection, antibody can block B cells from fighting pathogens
14.08.2018 | NIH/National Institute of Allergy and Infectious Diseases
First study on physical properties of giant cancer cells may inform new treatments
14.08.2018 | Brown University
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur
What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...
The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.
Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...
08.08.2018 | Event News
27.07.2018 | Event News
25.07.2018 | Event News
14.08.2018 | Information Technology
14.08.2018 | Life Sciences
14.08.2018 | Life Sciences