{"id":83,"date":"2019-07-04T01:24:50","date_gmt":"2019-07-04T01:24:50","guid":{"rendered":"http:\/\/wickedsister.evit.com.au\/?p=83"},"modified":"2019-07-04T01:24:50","modified_gmt":"2019-07-04T01:24:50","slug":"brains-really-grow-back-neurons","status":"publish","type":"post","link":"https:\/\/wickedsister.evit.com.au\/index.php\/2019\/07\/04\/brains-really-grow-back-neurons\/","title":{"rendered":"Brains Really Grow Back Neurons"},"content":{"rendered":"\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/static.scientificamerican.com\/sciam\/cache\/file\/52B19135-A87E-4900-8787C55A19925989_source.jpg?w=590&amp;h=800&amp;4482D8A9-1F12-45E6-8466C64DBDD4C9C3\" alt=\"Does the Adult Brain Really Grow New Neurons?\"\/><figcaption>Credit:&nbsp;<a href=\"https:\/\/www.gettyimages.com\/license\/736973125\" target=\"_blank\" rel=\"noreferrer noopener\">Getty Images<\/a><\/figcaption><\/figure>\n\n\n\n<p class=\"has-background has-vivid-cyan-blue-background-color\">The observation that the human brain churns out new neurons throughout life is one of the biggest neuroscience discoveries of the past 20 years. The idea has captured immense popular and scientific interest\u2014not least, because of hopes the brain\u2019s regenerative capacity might be harnessed to boost cognition or to treat injury or disease. In nonhuman animals the continued production of new neurons has been linked to improved learning and memory, and possibly even mood regulation.<\/p>\n\n\n\n<p>But new findings in humans, reported online in&nbsp;<a href=\"http:\/\/nature.com\/articles\/doi:10.1038\/nature25975\"><em>Nature<\/em><\/a>&nbsp;on Wednesday, pump the brakes on this idea. In a direct challenge to earlier studies, the authors report adults produce no new cells in the hippocampus, a key hub for processing memories.<\/p>\n\n\n\n<p>The study signals the latest volley in a debate over whether and to what extent the human brain produces new cells in adulthood. Scientists originally believed the brain stopped making neurons at or shortly after birth. But research in the 1960s began rolling back this dogma. Emerging techniques for labeling dividing cells revealed the birth of new neurons\u2014a process called neurogenesis\u2014in parts of the adult rat brain. Over the next few decades scientists discovered adult neurogenesis in other species, including birds, mice and monkeys. And in a 1998 landmark study researchers reported the phenomenon in the adult human hippocampus. Another major study in 2013 corroborated those findings, estimating that about 1,400 hippocampal neurons are made daily in adult brains.<\/p>\n\n\n\n<figure><iframe loading=\"lazy\" src=\"https:\/\/tpc.googlesyndication.com\/safeframe\/1-0-35\/html\/container.html\" width=\"300\" height=\"250\"><\/iframe><figcaption>ADVERTISEMENT<\/figcaption><\/figure>\n\n\n\n<p>The latest results push the pendulum back, raising eyebrows\u2014even among the study researchers themselves. \u201cWe went into the hippocampus expecting to see many young neurons,\u201d says senior author&nbsp;<a href=\"http:\/\/ablab.ucsf.edu\/\">Arturo Alvarez-Buylla<\/a>, a neuroscientist at the University of California, San Francisco. \u201cWe were surprised when we couldn\u2019t find them.\u201d<\/p>\n\n\n\n<p>Together with collaborators in China, Spain and Los Angeles, Alvarez-Buylla\u2019s team examined 59 human brain samples ranging in age from fetal stages up to 77 years, obtained either postmortem or during brain surgery. The researchers sliced the tissue, then applied various antibodies that would signal the presence of young neurons as well as dividing cells, which give rise to new neurons. They found clear evidence of new neurons forming in prenatal and neonatal samples, but this fell off sharply within the first year of life. By ages seven and 13, only a few isolated young neurons appeared. In adult samples the researchers found no new neurons.<\/p>\n\n\n\n<p>\u201cI feel vindicated,\u201d says neuroscientist&nbsp;<a href=\"http:\/\/bbs.yale.edu\/people\/pasko_rakic.profile\">Pasko Rakic<\/a>, a longtime, outspoken skeptic of neurogenesis in human adults. The Yale University researcher\u2019s work suggests adult monkeys produce significantly fewer new neurons than do adult rodents. Rakic favors the idea that in primates, including humans, the absence or near absence of adult neurogenesis could help prevent disruptions to complex neural circuits. \u201cThis paper not only shows very convincing evidence of a lack of neurogenesis in the adult human hippocampus but also shows that some of the evidence presented by other studies was not conclusive,\u201d he says.<\/p>\n\n\n\n<p>Others not associated with the work interpret the findings in less stark terms. \u201cIt\u2019s by far the best database that has ever been put together on cell turnover in the adult human hippocampus,\u201d says Steven Goldman, a neurologist at the&nbsp;<a href=\"https:\/\/www.urmc.rochester.edu\/labs\/goldman.aspx\">University of Rochester Medical Center<\/a>&nbsp;and the&nbsp;<a href=\"http:\/\/ctn.ku.dk\/about\/steven_goldman\/\">University of Copenhagen<\/a>. \u201cThe jury is still out about whether there are&nbsp;<em>any<\/em>&nbsp;new neurons being produced,\u201d he says, adding that if there is neurogenesis, \u201cit\u2019s just not at the levels that have been presumed by many.\u201d Goldman has had his doubts since the early 2000s, when his group isolated neural precursor cells from the adult human brain. These cells, although capable of producing neurons in a dish, were scarce in the brain. Goldman believes the latest study will help temper runaway expectations adult neurogenesis can be leveraged to treat patients\u2019 memory or mood disorders.<\/p>\n\n\n\n<p>Yet others argue it is too early to change course based on the new results.&nbsp;<a href=\"http:\/\/www.cmb.ki.se\/research\/frisen\/\">Jonas Fris\u00e9n<\/a>, senior author of the 2013 study, stands by his original findings. \u201cSince it is a rare phenomenon they are looking for, they may just not have looked carefully enough,\u201d he says. The 1,400 neurons Fris\u00e9n\u2019s team estimated arise daily comprise a small fraction of the tens of millions of hippocampal cells. To find them, his group at the Karolinska Institute in Stockholm studied people who were exposed to cold war nuclear bomb testing, and incorporated a radioactive carbon isotope into their dividing cells over many years. This cumulative measure, Fris\u00e9n argues, can detect neurogenesis better than antibodies that label new neurons at a single time point.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The observation that the human brain churns out new neurons throughout life is one of the biggest neuroscience discoveries of the past 20 years. The idea has captured immense popular and scientific interest\u2014not least, because of hopes the brain\u2019s regenerative capacity might be harnessed to boost cognition or to treat injury or disease. In nonhuman&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-83","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/posts\/83","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/comments?post=83"}],"version-history":[{"count":1,"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/posts\/83\/revisions"}],"predecessor-version":[{"id":84,"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/posts\/83\/revisions\/84"}],"wp:attachment":[{"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/media?parent=83"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/categories?post=83"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wickedsister.evit.com.au\/index.php\/wp-json\/wp\/v2\/tags?post=83"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}