reactions to threats<\/a>\u2014controls the groups of cells in the brain stem that send signals to muscles used for vocalization.<\/p>\nThe marine mammal brains, however, have a direct connection between the vocal motor cortex and the groups of cells controlling vocal muscles. That connection bypasses the mid-brain region.<\/p>\n
The researchers hypothesize that most animals lack vocal flexibility due to their inability to \u201cunlock\u201d this automatic response mechanism from vocalization.<\/p>\n
Seals and sea lions have loosened this automatic control through their development of exquisite breathing and swallowing capabilities allowing them to hunt and eat underwater. Sea lions, for example, can stay underwater for an average of 10-20 minutes while some seal species can dive without surfacing for up to two hours.<\/p>\n
\u201cWe\u2019ve discovered an ecological recipe for how a mammal might evolve a vocally flexible brain,\u201d says Cook, who is now associate professor of marine mammal science at New College of Florida.<\/p>\n
\u201cBy broadening the scope and using these neuroimaging techniques to compare more mammalian species wired to have vocal flexibility with those that are not, we might be able to build up an evolutionary tree for language,\u201d adds Berns.<\/p>\n
MRI scans reveal information about the architecture of a brain\u2014known as gray matter. Diffusion MRI provides information about how molecules move through biological tissues, mapping the connective pathways of a brain\u2014known as white matter.<\/p>\n
The technique of using diffusion MRI on a non-living brain was developed by coauthor Karla Miller at the University of Oxford to study Alzheimer\u2019s disease in human brains.<\/p>\n
\u201cBecause dead brains don\u2019t move, and don\u2019t mind holding still for hours on end, we can acquire extremely high-quality data,\u201d Miller explains.<\/p>\n
The technique has since been used in some primate and rodent studies.<\/p>\n
Berns helped pioneer the use of diffusion MRI in a range of other animals, including brains preserved in museum collections. He led a 2017 study that successfully mapped the connectivity in the brains of two extinct thylacines, or Tasmanian tigers. The brains had been stored in formaldehyde for more than 100 years.<\/p>\n
\u201cI believe we hold the record for getting diffusion MRI data out of the oldest brain specimens,\u201d Berns says.<\/p>\n
Cook came to the Berns lab from the Institute of Marine Sciences at the University of California, Santa Cruz, where he studied the neurobiology and behavior of pinnipeds\u2014carnivorous, fin-footed marine mammals that include seals, sea lions and walruses.<\/p>\n
\u201cMany people have an impression of seals and sea lions as just fat, furry slugs, laying on a beach and barking,\u201d Cook says.<\/p>\n
In reality, he adds, they are intelligent animals with brains close in size to those of chimpanzees.<\/p>\n
\u201cI really enjoy teaching them hearing and memory tasks,\u201d Cook says. \u201cThey have a tremendous drive to learn new things and are quick at picking up new behaviors.\u201d<\/p>\n
Both Berns and Cook were intrigued by the unique vocal capabilities of these marine mammals, which offer a rare opportunity to study vocal dexterity in a non-human animal.<\/p>\n
Hoover, a harbor seal who could mimic his keeper\u2019s Boston accent, is the most famous example of this plasticity. More recently, researchers at the University of St. Andrews in Scotland trained gray seals to imitate human voices humming \u201cTwinkle, Twinkle Little Star\u201d and the theme to Star Wars.<\/p>\n
The researchers decided to use diffusion MRI to gain a neurobiological window into how this vocal flexibility may have developed in pinnipeds.<\/p>\n
They acquired brains from four California sea lions, four harbor seals and three northern elephant seals that died of natural causes or had to be euthanized at a California veterinary rehabilitation center. They compared those brains to the brains of four coyotes that had to be euthanized at a United States Department of Agriculture facility in Utah.<\/p>\n
Brain data in hand, the researchers painstakingly mapped out specific circuits related to vocal control and vocal learning. They identified and carefully delineated the 15 relevant regions in each animal\u2019s brain. That allowed them to make comparisons between individuals and species.<\/p>\n
The most striking result showed that the pinnipeds have a neural pathway that links vocalization directly to neurons controlling the larynx\u2014a bypass that allows them to consciously control the muscles used in vocalization.<\/p>\n
The data also revealed distinctions in pathways connecting auditory and vocal brain systems. The elephant seals and harbor seals all showed robust auditory-vocal motor connections, but the coyotes did not.<\/p>\n
An additional finding may help explain the ability of seals to mimic novel sounds. Parrots and humans have special connections between the thalamus\u2014the brain\u2019s sensorimotor waystation\u2014and the vocal motor cortex. In the current study, the harbor seals showed much stronger connections between these regions than all the other species.<\/p>\n
The researchers are building on these findings through a similar brain study in whales, dolphins and porpoises, another group of marine mammals with impressive vocal abilities.<\/p>\n
\u201cAll animals can learn,\u201d Cook says. \u201cAnd almost all birds and mammals communicate with their voices. The paradox of why so few animals can learn to control their calls is an irresistible scientific mystery.\u201d<\/p>\n
Source: Emory University<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"Share this Article You are free to share this article under the Attribution 4.0 International license. Neuroscientists have…\n","protected":false},"author":2,"featured_media":364641,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[85,61,60,82,133697],"class_list":["post-364640","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-evolution","tag-ie","tag-ireland","tag-science","tag-seals"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/364640","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=364640"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/364640\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/364641"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=364640"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=364640"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=364640"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}