![\"\"](\"https:\/\/www.salk.edu\/wp-content\/uploads\/2015\/01\/2070-touch.jpg\")
<\/p>\nSalk Institute researchers mapped neural circuits in the spinal cord that process light touch signals from the feet, a critical function for fine motor tasks, such as walking on ice. This image shows this neural circuitry in a mouse spinal cord. The red cells are ROR\u03b1 neurons, which merge signals coming from neural fibers coming from the brain and limbs (both colored blue).<\/p>\n
Click here<\/a> for a high-resolution image.<\/p>\n \nImage: Courtesy of Steeve Bourane\/Salk Institute for Biological Studies\n<\/p>\n<\/div>\n \n\u201cWhen we stand and walk, touch sensors on the soles of our feet detect subtle changes in pressure and movement. These sensors send signals to our spinal cord and then to the brain,\u201d says Martyn Goulding<\/a>, a Salk professor and senior author on the paper. \u201cOur study opens what was essentially a black box, as up until now we didn\u2019t know how these signals are encoded or processed in the spinal cord. Moreover, it was unclear how this touch information was merged with other sensory information to control movement and posture.\u201d\n<\/p>\n \nWhile the brain\u2019s role in cerebral achievements such as philosophy, mathematics and art often take center stage, much of what the nervous system does is to use information gathered from our environment to guide our movements. Walking across that icy parking lot, for instance, engages a number of our senses to prevent us from falling. Our eyes tell us whether we\u2019re on shiny black ice or damp asphalt. Balance sensors in our inner ear keep our heads level with the ground. And sensors in our muscles and joints track the changing positions of our arms and legs.\n<\/p>\n \nEvery millisecond, multiple streams of information, including signals from the light touch transmission pathway that Goulding\u2019s team has identified, flow into the brain. One way the brain handles this data is by preprocessing it in sensory way stations such as the eye or spinal cord. The eye, for instance, has a layer of neurons and light sensors at its back that performs visual calculations\u2013a process known as \u201cencoding\u201d\u2013before the information goes on to the visual centers in the brain. In the case of touch, scientists have long thought that the neurological choreography of movement relies on data-crunching circuits in the spinal cord. But until now, it has been exceedingly difficult to precisely identify the types of neurons involved and chart how they are wired together.\n<\/p>\n \nIn their study, the Salk scientists demystified this fine-tuned, sensory-motor control system. Using cutting-edge imaging techniques that rely on a reengineered rabies virus, they traced nerve fibers that carry signals from the touch sensors in the feet to their connections in the spinal cord. They found that these sensory fibers connect in the spinal cord with a group of neurons known as ROR\u03b1 neurons, named for a specific type of molecular receptor found in the nucleus of these cells. The ROR\u03b1 neurons in turn are connected by neurons in the motor region of brain, suggesting they might serve as a critical link between the brain and the feet.\n<\/p>\n \nFrom right: Steeve Bourane, Antoine Dalet, Stephanie Koch, Chris Padilla, Cathy Charles, Graziana Gatto, Tommie Velasquez and Martyn Goulding<\/p>\n Click here<\/a> for a high-resolution image.<\/p>\n \nImage: Courtesy of the Salk Institute for Biological Studies\n<\/p>\n<\/div>\n \nWhen Goulding\u2019s team disabled the ROR\u03b1 neurons in the spinal cord using genetically modified mice developed at Salk, they found that these mice were substantially less sensitive to movement across the surface of the skin or to a sticky piece of tape placed on their feet. Despite this, the animals were still able to walk and stand normally on flat ground.\n<\/p>\n \nHowever, when the researchers had the animals walk across a narrow, elevated beam, a task that required more effort and skill, the animals struggled, performing more clumsily than animals with intact ROR\u03b1 neurons. The scientists attribute this to the animals\u2019 reduced ability to sense skin deformation when a foot was slipping off the edge and respond accordingly with small adjustments in foot position and balance\u2013motor skills similar to those necessary for balancing on ice or other slippery surfaces.\n<\/p>\n \nAnother important characteristic of the ROR\u03b1 neurons is that they don\u2019t just receive signals from the brain and the light touch sensors, but also directly connect with neurons in the ventral spinal cord that control movement. Thus, they are at the center of a \u201cmini-brain\u201d in the spinal cord that integrates signals from the brain with sensory signals to make sure the limbs move correctly.\n<\/p>\n \n\u201cWe think these neurons are responsible for combining all of this information to tell the feet how to move,\u201d says Steeve Bourane, a postdoctoral researcher in Goulding\u2019s lab and first author on the new paper. \u201cIf you stand on a slippery surface for a long time, you\u2019ll notice your calf muscles get stiff, but you may not have noticed you were using them. Your body is on autopilot, constantly making subtle corrections while freeing you to attend to other higher-level tasks.\u201d\n<\/p>\n \nThe team\u2019s study represents the beginning of a new wave of research that promises to provide precise and comprehensive explanations for how the nervous system encodes and integrates sensory information to generate both conscious and unconscious movement.\n<\/p>\n \n\u201cHow the brain creates a sensory percept and turns it into an action is one of the central questions in neuroscience,\u201d adds Goulding. \u201cOur work is offering a really robust view of neural pathways and processes that underlie the control of movement and how the body senses its environment. We\u2019re at the beginning of a real sea change in the field, which is tremendously exciting.\u201d\n<\/p>\n \nOther authors on the paper were Katja S. Grossmann, Olivier Britz, Antoine Dalet, Marta Garcia Del Barrio, Floor J. Stam, Lidia Garcia-Campmany and Stephanie Koch, all of the Salk Institute.\n<\/p>\n \nThe research was funding by National Institutes of Health<\/a> (Grants NS080586, NS086372 and NS072031), the Catharina Foundation, the Humboldt \nAbout the Salk Institute for Biological Studies:<\/strong> \nFaculty achievements have been recognized with numerous honors, including Nobel Prizes and memberships in the National Academy of Sciences. Founded in 1960 by polio vaccine pioneer Jonas Salk, MD, the Institute is an independent nonprofit organization and architectural landmark. <\/p>","protected":false},"featured_media":0,"template":"","faculty":[75],"disease-research":[124,464],"class_list":["post-2524","disclosure","type-disclosure","status-publish","hentry","faculty-martyn-goulding","disease-research-neuroscience-and-neurological-disorders","disease-research-perception"],"acf":[],"yoast_head":"\n![\"\"](\"https:\/\/www.salk.edu\/wp-content\/uploads\/2015\/01\/2070.jpg\")
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\nFoundation<\/a> and Joan and Irwin Jacobs, through Salk\u2019s Innovation Grants Program.\n<\/p>\n
\nThe Salk Institute for Biological Studies is one of the world’s preeminent basic research institutions, where internationally renowned faculty probes fundamental life science questions in a unique, collaborative, and creative environment. Focused both on discovery and on mentoring future generations of researchers, Salk scientists make groundbreaking contributions to our understanding of cancer, aging, Alzheimer’s, diabetes and infectious diseases by studying neuroscience, genetics, cell and plant biology, and related disciplines.\n<\/p>\n