{"id":495,"date":"2021-12-17T05:00:49","date_gmt":"2021-12-17T04:00:49","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=106623"},"modified":"2021-12-17T05:15:11","modified_gmt":"2021-12-17T04:15:11","slug":"neuroplasticity-a-neurologist-explains-how-the-brain-recovers-from-injury","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/neuroplasticity-a-neurologist-explains-how-the-brain-recovers-from-injury\/","title":{"rendered":"Neuroplasticity: A neurologist explains how the brain recovers from injury"},"content":{"rendered":"

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By Hayley Bennett\n \t\t<\/p>

Published: Friday, 17 December 2021 at 12:00 am<\/p>

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Some animals have incredible regenerative abilities, growing new legs and tails to replace lost ones. Fish and salamanders can even grow new brain cells to repair damaged portions of their brains. As mammals, though, our capacity for regeneration is more limited, particularly where the brain is concerned.<\/p>\n

\u201cLower vertebrates keep on replacing neurons quite happily throughout their life, but mammals don\u2019t,\u201d explains James Fawcett<\/a>, a neuroscientist at the University of Cambridge. \u201cWe stop making new neurons before birth, pretty much, except for one or two small parts of the nervous system.\u201d<\/p>\n

This means that whilst we can repair a cut to our skin by growing new skin cells, we can\u2019t recover from a brain injury in the same way. Instead, our brain\u2019s only option is to work with the existing neurons \u2013 cells that carry all the information required for us to think, move and perform our normal bodily functions.<\/p>\n

If the odd brain cell goes offline here or there, it\u2019s not usually a problem, but the impact of a major brain injury depends on the type and site of injury, and how many neurons have been lost.<\/p>\n

To some extent, what\u2019s left can be remodelled \u2013 the brain has what we call \u2018neuroplasticity\u2019. Think of your brain as if it were Google Maps or another route planner. If one of the roads on the quickest route is being dug up, Google Maps will find you another route, even if it takes a bit longer.<\/p>\n

Similarly, because each brain cell has thousands of different connections, your brain is capable of some fairly extensive re-routing of its signalling, says Mark Ashley<\/a>, CEO of the US-based Centre for Neuro Skills, which helps patients to recover from brain and spinal cord injuries. \u201cWe may lose a highway or two, or several highways, but theoretically, we could find other highways.\u201d<\/p>\n

This means when the brain is injured it can try to bypass the damaged cells by forming new connections between neurons in order to drive the lost functions. Neuroplastic processes also occur when we\u2019re learning new skills, but with a major brain injury it can result in some dramatic remodelling, even to the extent of entire functions being transferred to different parts of the brain \u2013 hearing, for example, can be taken over by the visual cortex, and vice versa.<\/p>\n

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\u00a9 Anson Chan<\/span><\/figcaption><\/div>\n

Neuroplasticity relies on the nerve cells themselves, as well as support cells called glial cells that help make new connections and repair myelin, which is the protective covering around a nerve fibre that speeds up nerve impulses.<\/p>\n

The nerve fibres (axons) that carry the signals do also have some capacity for sprouting new branches, when the main body of the nerve cell is still intact. As Fawcett explains, though, regeneration of nerve fibres that have been cut, as in a typical spinal cord injury, is restricted by the formation of scar tissue \u2013 which hinders regrowth \u2013 and normal changes during maturation that stop them regenerating their axons.<\/p>\n

\u201cThere\u2019s some genetic programme that goes with maturation that turns off regeneration,\u201d Fawcett says. His team of researchers have made some headway in regeneration of axons in the spinal cords of mice and rats, but the fibres are much longer and trickier to regrow in humans.<\/p>\n

Rehabilitation programmes focus on getting the most out of the brain\u2019s natural neuroplasticity and could involve up to 17 hours per day of therapy \u2013 the more intensive the better, Ashley says, as this constant \u2018demand for function\u2019 encourages the brain to rebuild in order to respond.<\/p>\n

However, our understanding of the brain is limited enough that trying to predict how a patient will recover based on brain imaging can be futile. \u201cI\u2019ve adopted the notion that the early predictions of recovery are far more likely to be incorrect than correct,\u201d says Ashley, who adds that he\u2019s often \u201cpleasantly surprised\u201d by what\u2019s achievable, given access to the right treatment.<\/p>\n