{"id":1827,"date":"2018-09-23T16:33:23","date_gmt":"2018-09-23T07:33:23","guid":{"rendered":"http:\/\/163.180.4.222\/lab\/?p=1827"},"modified":"2019-10-15T18:38:42","modified_gmt":"2019-10-15T09:38:42","slug":"a-new-way-to-capture-the-brains-electrical-symphony","status":"publish","type":"post","link":"https:\/\/biochemistry.khu.ac.kr\/lab\/?p=1827","title":{"rendered":"A new way to capture the brain\u2019s electrical symphony"},"content":{"rendered":"

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How voltage readings from individual neurons could power the next revolution in neuroscience.<\/h5>\n

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Illustration by Joanna Gebal<\/p>\n<\/figcaption><\/figure>\n<\/div>\n

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Biophysicist Adam Cohen was strolling around San Francisco, California, in 2010, when a telephone call caught him by surprise. \u201cWe have a signal,\u201d said the caller. Nearly 5,000 kilometres away, in Cambridge, Massachusetts, his collaborators had struck gold. After months of failed experiments, the researchers had found a fluorescent protein that allowed them to watch signals as they passed between neurons.<\/p>\n

But there was something weird going on. When Cohen got back to his lab at Harvard University, he learned that all the recordings of the experiment showed a strange progression. At first, neurons decorated with the protein flashed nicely as electric impulses whizzed through them. But then the cells turned into bright blobs. \u201cHalfway through each recording, the signal would go all wild,\u201d Cohen says.<\/p>\n

So he decided to join his team during an experiment. \u201cWhen they started the recording, they would sit there holding their breath,\u201d Cohen says. But as soon as they realized it was working, they would celebrate, \u201cdancing and running around the room\u201d.<\/p>\n

In their exuberance, they were letting the light from a desk lamp shine right onto the microscope. \u201cWe were actually recording our excitement,\u201d says Daniel Hochbaum, then a graduate student in Cohen\u2019s group. They toned down their celebrations, and a year later, the team published its study1<\/a><\/sup>\u00a0\u2014 one of the first to show that a fluorescent protein engineered into specific mammalian neurons could be used to track individual electric impulses in real time.<\/p>\n

Neuroscientists have tried for decades to observe the swift electrical signals that are a major component of the brain\u2019s language. Although electrodes, the workhorse for measuring voltage, can reliably record the activity of individual neurons, they struggle to capture the signals of many, particularly for prolonged periods. But in the past two decades, scientists have found a way to embed fluorescent, voltage-indicating proteins right into the cell membranes of neurons. With the right kind of microscope, they can then see cells lighting up as they talk to each other \u2014 be it in a whisper or a shout. Voltage imaging can also record electrical chatter between many neurons at once, and then average those signals across large chunks of brain tissue. This helps researchers to study the brain\u2019s electrical activity across different spatial scales, by listening not only to the voices of individual cells but also to \u201cthe roar of the crowd\u201d, Cohen says.<\/p>\n

In the past 5 years, scientists have published about 1,000 papers on the topic, and major funding schemes such as the US National Institutes of Health\u2019s BRAIN initiative have sped up the development of new types of genetically engineered voltage indicators. In the hope of finding better variants, some groups have come up with strategies to screen millions of proteins for desired characteristics such as brightness. One such approach has identified an indicator that\u2019s twice as bright as similar sensors developed just four years earlier2<\/a><\/sup>.<\/p>\n

As these proteins improve, and advances in microscopy make it easier to see them, scientists hope to illuminate neuroscience\u2019s biggest puzzle: how the brain\u2019s cells work together to transform a system of electrical pulses into thoughts, actions and emotions. Researchers are still struggling to catch the full range of activity and to devise ways to see nerves firing fast and deep within brain tissue. But if advances can solve these technical challenges, \u201cit would be revolutionary\u201d, says Rafael Yuste, who studies the function of neural circuits at Columbia University in New York City.<\/p>\n

High-speed process<\/h6>\n

The average human brain contains about 120 billion neurons, which constantly receive and send information through branch-like appendages called dendrites. Chemical or electrical signals that reach the dendrites produce small voltage changes across the cell\u2019s membrane, which are routed to the cell body. When the sum of the voltage changes reaches a point of no return, called a threshold, the neuron fires a large electrical spike \u2014 an action potential. This jolt whizzes at speeds of up to 150 metres per second along a neuronal branch, known as an axon, to another set of branching appendages. Here, chemical or electrical signals pass the information on to the next set of dendrites.<\/p>\n

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