{"id":107536,"date":"2024-09-27T14:07:44","date_gmt":"2024-09-27T07:07:44","guid":{"rendered":"https:\/\/hotvideos24.online\/?p=107536"},"modified":"2024-09-27T14:07:44","modified_gmt":"2024-09-27T07:07:44","slug":"how-reflexes-shape-smooth-movement","status":"publish","type":"post","link":"https:\/\/hotvideos24.online\/?p=107536","title":{"rendered":"How Reflexes Shape Smooth Movement"},"content":{"rendered":"<p> <script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-3711241968723425\"\r\n     crossorigin=\"anonymous\"><\/script>\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:block\"\r\n     data-ad-format=\"fluid\"\r\n     data-ad-layout-key=\"-fb+5w+4e-db+86\"\r\n     data-ad-client=\"ca-pub-3711241968723425\"\r\n     data-ad-slot=\"7910942971\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><br \/>\n<\/p>\n<div>\n<p><strong>Summary: <\/strong>Researchers have uncovered how the spinal cord helps modulate reflexes to allow for smooth, voluntary movements. Using simulations, the study shows how circuits within the spinal cord regulate stretch reflexes, preventing disruptions during skilled movements like reaching.<\/p>\n<p>This research provides a new perspective on how the spinal cord collaborates with the brain, challenging the notion that movement is solely brain-controlled. The findings could pave the way for better treatments for neurological conditions like stroke and cerebral palsy that affect motor control.<\/p>\n<p><strong>Key Facts<\/strong>:<\/p>\n<ul class=\"wp-block-list\">\n<li>The spinal cord plays a key role in modulating reflexes for smooth movements.<\/li>\n<li>This spinal control helps prevent movement disruptions caused by reflexes.<\/li>\n<li>The findings could inform treatments for movement disorders like stroke and cerebral palsy.<\/li>\n<\/ul>\n<p><strong>Source: <\/strong>USC<\/p>\n<p><strong>How did the bodies of animals, including ours, become such fine-tuned movement machines? <\/strong><\/p>\n<p>How vertebrates coordinate the eternal tug-o-war between involuntary reflexes and seamless voluntary movements is a mystery that Francisco Valero-Cuevas\u2019 Lab in USC Alfred E. Mann Department of Biomedical Engineering, set out to understand.<\/p>\n<p>The Lab\u2019s newest computational paper published in the\u00a0<em>Proceedings of the National Academy of Sciences (<\/em>PNAS) adds to the thought leadership about the processing of sensory information and control of reflexes during voluntary movements\u2014with implications as to how its disruption could give rise to motor disorders in neurological conditions like stroke, cerebral palsy, and Parkinson\u2019s disease.\u00a0<\/p>\n<figure class=\"wp-block-image size-full\"><picture fetchpriority=\"high\" decoding=\"async\" class=\"wp-image-104753\"><source type=\"image\/webp\" srcset=\"https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence.jpg.webp 1200w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-300x200.jpg.webp 300w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-770x513.jpg.webp 770w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-1155x770.jpg.webp 1155w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-370x247.jpg.webp 370w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-293x195.jpg.webp 293w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-150x100.jpg.webp 150w\" sizes=\"(max-width: 1200px) 100vw, 1200px\"\/><img fetchpriority=\"high\" decoding=\"async\" width=\"1200\" height=\"799\" src=\"https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence.jpg\" alt=\"This shows an arm.\" srcset=\"https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence.jpg 1200w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-300x200.jpg 300w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-770x513.jpg 770w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-1155x770.jpg 1155w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-370x247.jpg 370w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-293x195.jpg 293w, https:\/\/neurosciencenews.com\/files\/2024\/09\/reflex-motor-control-neurosicence-150x100.jpg 150w\" sizes=\"(max-width: 1200px) 100vw, 1200px\"\/> <\/picture><figcaption class=\"wp-element-caption\">The study, Niyo says, proposes \u201ca theoretically new mechanism to modulate spinal reflexes at the same spinal cord level as stretch reflexes.\u201d Credit: Neuroscience News<\/figcaption><\/figure>\n<p>Do you remember the pediatrician tapping your knee to see if you had a strong involuntary knee-jerk reaction? This was to test the stretch reflexes in your spinal cord, which resist muscle stretching to give you muscle tone to hold your body up against gravity for example, fast corrections after tripping.<\/p>\n<p>So, how exactly those reflexes are modulated or inhibited to allow smooth, voluntary movement has been debated since Charles Scott Sherrington\u2019s foundational work in the 1880s (yes, the 1880s!).<\/p>\n<p>This new work cuts directly into critical debates about how the ancient spinal cord and the relatively new human brain interact to produce smooth movements and how some neurological conditions disrupt this fine balance and produce slow, inaccurate, jerky, etc. movements in neurological conditions.<\/p>\n<p>The study, led by Biomedical engineering doctoral student Grace Niyo, sheds light on a possible undiscovered system or circuitry at play within the spinal cord that, when working properly, \u201cmodulates\u201d reflexes during voluntary movements. The study, Niyo says, proposes \u201ca theoretically new mechanism to modulate spinal reflexes at the same spinal cord level as stretch reflexes.\u201d<\/p>\n<p>Valero-Cuevas, Professor of Biomedical Engineering, Aerospace and Mechanical Engineering, Electrical and Computer Engineering, Computer Science, and Biokinesiology and Physical Therapy at USC, is the corresponding author of the paper \u201cA computational study of how \u03b1- to \u03b3-motoneurone collateral can mitigate velocity-dependent stretch reflexes during voluntary movement.\u00a0<\/p>\n<p>He says, \u201cReflexes are sophisticated and ancient low-level information exchange mechanisms that co-evolved and co-adapted with later developments like the human brain\u2026understanding their collaboration with the brain is critical to understanding movement in health and disease.\u201d\u00a0<\/p>\n<p>Valero-Cuevas says, \u201cWe are constantly benefiting from, and modulating stretch reflexes, whether we realize it or not as we stand, move and act.\u201d<\/p>\n<p>Professor Valero-Cuevas\u2019 lab is dedicated to understanding neuromuscular control in animals and robots, with implications for clinical rehabilitation for human mobility.\u00a0<\/p>\n<p>He explains, \u201cAlthough our brain is highly sophisticated, we need to recognize the value and power of the ancient spinal cord\u2014which has allowed all vertebrates to thrive for millions of years before large brains were even possible. We would like to understand how the spinal cord is able to regulate smooth movements, even with minimal brain control, as we know happens in amphibians and reptiles.<\/p>\n<p>\u201cThis perspective could have important implications for understanding, and possibly treating, movement disorders in neurological conditions that affect the brain, spinal cord, or both\u2014and also for creating biologically-inspired prostheses or robots that move smoothly using simulated spinal cords.\u201d<\/p>\n<p>The simulation experiment: To test whether and how a spinal circuit can allow voluntary movements by modulating or inhibiting movement perturbations that arise from stretch reflexes, the team, led by Niyo, created a biomechanical model of the arm of a macaque monkey in the physics simulator software called MuJoCo, generating over one thousand reaching movements.<\/p>\n<p>The simple stretch reflex rule is that muscles being stretched will tend to oppose the stretch, while muscles that are shortening do not show stretch reflexes.<\/p>\n<p>hey first demonstrated that unmodulated stretch reflexes indeed produce a self-perturbation that disrupts voluntary arm movements. They then implemented a simple spinal circuit whereby the same neurons in the spinal cord that control muscle force (called alpha motoneurons) also scale (i.e., modulate) the stretch reflex proportionally to their level of muscle excitation. That is, highly excited muscles would have strong stretch reflex responses if stretched, and vice versa.<\/p>\n<p>They found that this simple rule\u2014that it is physiologically possible given the known projections from alpha motoneurones (also called collaterals) to the reflex circuitry can\u2014by itself\u2014largely correct the self-perturbations from stretch reflexes to produce smooth and accurate voluntary movements.\u00a0\u00a0<\/p>\n<p>From a modern engineering perspective, one might compare this to \u201cedge computing,\u201d says Valero-Cuevas, which is the idea that information processing is done at the source (limb sensors and the spinal cord) instead of exclusively at the central command center (the brain)\u2014much like some apps in your phone that pre-processes information to be sent to a cloud server.\u00a0\u00a0<\/p>\n<p>Valero-Cuevas makes the mechanical analogy to\u00a0these low-level connections to the reflex circuitry being like the \u201ctraining wheels on a bicycle that are there to allow you to have fun, and catch you should you make a mistake while you learn to ride your bicycle.\u201d\u00a0<\/p>\n<p>These circuits\u00a0may help you produce novel voluntary movements with minimal perturbations but leave open the possibility of the brain and cerebellum to also refine and learn to control reflexes as your nervous system matures or gains enough experience.\u00a0<\/p>\n<p><strong>Implications:<\/strong> Beyond better understanding movement disorders, Niyo says this knowledge could be a starting point for experimentalists to start looking for and testing for such spinal circuits. \u201cThis work could also inspire and guide new therapies at the appropriate level of the nervous system for treatment of movement disorders like stroke and cerebral palsy,\u201d say Niyo and Valero-Cuevas.\u00a0<\/p>\n<p>The study\u2019s additional co-authors include Lama I. Almofeez, a PhD student in the USC Alfred E Man Department of Biomedical Engineering and Andrew Erwin, who at the time of the study was a Post-doctoral scholar in the USC Division of Biokinesiology and Physical Therapy.<\/p>\n<h2 class=\"wp-block-heading\">About this neuroscience research news<\/h2>\n<p class=\"has-background\" style=\"background-color:#ffffe8\"><strong>Author: <\/strong><a href=\"http:\/\/neurosciencenews.com\/cdn-cgi\/l\/email-protection#bbdad6c2d9d7ced6defbcec8d895dedfce\" target=\"_blank\" rel=\"noreferrer noopener\">Amy Blumenthal<\/a><br \/><strong>Source: <\/strong><a href=\"https:\/\/usc.edu\" target=\"_blank\" rel=\"noreferrer noopener\">USC<\/a><br \/><strong>Contact: <\/strong>Amy Blumenthal \u2013 USC<br \/><strong>Image: <\/strong>The image is credited to Neuroscience News<\/p>\n<p class=\"has-background\" style=\"background-color:#ffffe8\"><strong>Original Research: <\/strong>Open access.<br \/>\u201c<a href=\"https:\/\/www.pnas.org\/doi\/10.1073\/pnas.2321659121\" target=\"_blank\" rel=\"noreferrer noopener\">A computational study of how \u03b1- to \u03b3-motoneurone collateral can mitigate velocity-dependent stretch reflexes during voluntary movement<\/a>\u201d by Francisco Valero-Cuevas et al. <em>PNAS<\/em><\/p>\n<hr class=\"wp-block-separator has-text-color has-pale-cyan-blue-color has-alpha-channel-opacity has-pale-cyan-blue-background-color has-background\"\/>\n<p><strong>Abstract<\/strong><\/p>\n<p><strong>A computational study of how \u03b1- to \u03b3-motoneurone collateral can mitigate velocity-dependent stretch reflexes during voluntary movement<\/strong><\/p>\n<p>The primary motor cortex does not uniquely or directly produce alpha motoneurone (\u03b1-MN) drive to muscles during voluntary movement. Rather, \u03b1-MN drive emerges from the synthesis and competition among excitatory and inhibitory inputs from multiple descending tracts, spinal interneurons, sensory inputs, and proprioceptive afferents.<\/p>\n<p>One such fundamental input is velocity-dependent stretch reflexes in lengthening muscles, which should be inhibited to enable voluntary movement.<\/p>\n<p>It remains an open question, however, the extent to which unmodulated stretch reflexes disrupt voluntary movement, and whether and how they are inhibited in limbs with numerous multiarticular muscles.<\/p>\n<p>We used a computational model of a Rhesus Macaque arm to simulate movements with feedforward \u03b1-MN commands only, and with added velocity-dependent stretch reflex feedback.<\/p>\n<p>We found that velocity-dependent stretch reflex caused movement-specific, typically large and variable disruptions to arm movements.<\/p>\n<p>These disruptions were greatly reduced when modulating velocity-dependent stretch reflex feedback (i) as per the commonly proposed (but yet to be clarified) idealized alpha-gamma (\u03b1-\u03b3) coactivation or (ii) an alternative \u03b1-MN collateral projection to homonymous \u03b3-MNs. We conclude that such \u03b1-MN collaterals are a physiologically tenable propriospinal circuit in the mammalian fusimotor system.<\/p>\n<p>These collaterals could still collaborate with \u03b1-\u03b3 coactivation, and the few skeletofusimotor fibers (\u03b2-MNs) in mammals, to create a flexible fusimotor ecosystem to enable voluntary movement.<\/p>\n<p>By locally and automatically regulating the highly nonlinear neuro-musculo-skeletal mechanics of the limb, these collaterals could be a critical low-level enabler of learning, adaptation, and performance via higher-level brainstem, cerebellar, and cortical mechanisms.<\/p>\n<p> <!-- Form created by Optin Forms plugin by WPKube: create beautiful optin forms with ease! --> <!-- https:\/\/wpkube.com\/ --><!--optinforms-form5-container--> <!-- \/ Optin Forms --> <\/div>\n<p><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-3711241968723425\"\r\n     crossorigin=\"anonymous\"><\/script>\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:block\"\r\n     data-ad-format=\"fluid\"\r\n     data-ad-layout-key=\"-fb+5w+4e-db+86\"\r\n     data-ad-client=\"ca-pub-3711241968723425\"\r\n     data-ad-slot=\"7910942971\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><br \/>\n<br \/><div data-type=\"_mgwidget\" data-widget-id=\"1660802\">\r\n<\/div>\r\n<script>(function(w,q){w[q]=w[q]||[];w[q].push([\"_mgc.load\"])})(window,\"_mgq\");\r\n<\/script>\r\n<br \/>\n<br \/><a href=\"https:\/\/neurosciencenews.com\/relexes-motor-contol-27698\/\">Source link <\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Summary: Researchers have uncovered how the spinal cord helps modulate reflexes to allow for smooth, voluntary movements. Using simulations, the study shows how circuits within the spinal cord regulate stretch &hellip; <a href=\"https:\/\/hotvideos24.online\/?p=107536\" class=\"more-link\">Read More<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-107536","post","type-post","status-publish","format-standard","hentry","category-health","entry"],"_links":{"self":[{"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/posts\/107536","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=107536"}],"version-history":[{"count":0,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=\/wp\/v2\/posts\/107536\/revisions"}],"wp:attachment":[{"href":"https:\/\/hotvideos24.online\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=107536"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=107536"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hotvideos24.online\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=107536"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}