{"id":2560,"date":"2015-09-02T00:00:00","date_gmt":"2015-09-02T07:00:00","guid":{"rendered":"https:\/\/vermont.salk.edu\/news-release\/scientists-see-motor-neurons-walking-in-real-time\/"},"modified":"2015-11-15T08:14:08","modified_gmt":"2015-11-15T16:14:08","slug":"scientists-see-motor-neurons-walking-in-real-time","status":"publish","type":"disclosure","link":"https:\/\/www.salk.edu\/de\/news-release\/scientists-see-motor-neurons-walking-in-real-time\/","title":{"rendered":"Scientists see motor neurons ‘walking’ in real time"},"content":{"rendered":"

\nLA JOLLA\u2013When you\u2019re taking a walk around the block, your body is mostly on autopilot\u2013you don\u2019t have to consciously think about alternating which leg you step with or which muscles it takes to lift a foot and put it back down. That\u2019s thanks to a set of cells in your spinal cord that help translate messages between your brain and your motor neurons, which control muscles.\n<\/p>\n

\nNow, for the first time, researchers have created a method to watch\u2013in real time\u2013the activity of those motor neurons. The new technology, developed by Salk scientists and published in Neuron<\/a><\/em> on September 2, 2015, is helping researchers understand how spinal cord cells make connections with motor neurons, and how clinicians might be able to repair those connections in patients with spinal cord injuries or neurodegenerative diseases like amyotrophic lateral sclerosis (ALS).\n<\/p>\n

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\nSalk scientists were able to selectively add fluorescent proteins to the nuclei of motor neurons (red) using cutting-edge genetic techniques to show how cells in the spinal cord synchronize many neurons at once to allow complex movements.\n<\/p>\n

Klicken Sie hier<\/a> f\u00fcr ein hochaufl\u00f6sendes Bild.<\/p>\n

\nBild: Mit freundlicher Genehmigung des Salk Institute for Biological Studies\n<\/p>\n<\/div>\n

\n\u201cUsing optical methods to be able to watch neuron activity has been a dream over the past decade,\u201d says Samuel Pfaff<\/a>, a professor in Salk\u2019s Genexpressionslabor<\/a>. \u201cNow, it\u2019s one of those rare times when the technology is actually coming together to show you things you hadn\u2019t been able to see before.\u201d\n<\/p>\n

\nIn the past, to measure the activity of neurons\u2013whether in the brain or extending throughout the body\u2013scientists relied on electrodes that could detect the change in electrical voltage inside a cell when it\u2019s activated. But it is tricky to use electrodes to simultaneously record the activity of many different neuron types at once to study how their activity is synchronized.\n<\/p>\n

\nTo get around this shortcoming of electrode readings, Pfaff\u2019s team used a fluorescent sensor protein called GCaMP6f that lights up whenever a neuron is activated. Unlike the electrodes, the protein could easily be added to many different cells at once. When Pfaff and his colleagues added GCaMP6f to motor neurons, they could watch with a microscope which cells were activated in a mouse spinal cord when chemicals that turn on walking circuits were added.\n<\/p>\n

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\nFrom left: Marito Hayashi, Samuel Pfaff and Christopher Hinckley<\/p>\n

Klicken Sie hier<\/a> f\u00fcr ein hochaufl\u00f6sendes Bild.<\/p>\n

\nBild: Mit freundlicher Genehmigung des Salk Institute for Biological Studies\n<\/p>\n<\/div>\n

\n\u201cYou don\u2019t need to do any kind of post-image processing to interpret this,\u201d says Pfaff. \u201cThese are just raw signals you can see through the eyepiece of a microscope. It\u2019s really a jaw-dropping kind of visualization for a neuroscientist.\u201d\n<\/p>\n

\nPfaff\u2019s group used the new method to answer a long-standing question about how a collection of cells in the spinal cord, called the locomotor central pattern generator (CPG), connects to the right motor neurons to allow movements like walking. The CPG, Pfaff says, is where relatively simple signals from the brain\u2013to walk forward, or move your hand off a hot stove\u2013are translated into more complex instructions for motor neurons to control muscles.\n<\/p>\n

\n\u201cOur nervous system has to make decisions and computations to tell different muscles to contract, or when not to contract, or the amount of force and speed to use when contracting,\u201d Pfaff explains. It\u2019s the CPG that helps make many of these computations, scientists believe. So normal movement requires that CPG neurons in the spinal cord connect to and control when motor neurons fire. But, until now, researchers didn\u2019t know exactly how the CPG cells forged these connections.\n<\/p>\n

\nBy tweaking the locations and identities of motor neurons, and then watching the resulting patterns of activation using their new fluorescent technique, Chris Hinckley in the Pfaff laboratory found that the CPG didn\u2019t rely solely on the cells\u2019 locations to connect to them. Instead, the genetic identity of each subtype of cells\u2013what makes those that control the quadriceps muscle different from those that control the calf muscle for instance\u2013is also important.\n<\/p>\n