Chimp's gestures share language roots

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In the first ever functional imaging study of the communicating chimpanzee brain, researchers have found that brain function in grunting and gesturing chimpanzees closely parallels that in actively communicating humans, according to a linkurl:paper;http://www.current-biology.com/content/article/abstract?uid=PIIS0960982208000961 published online today in __Current Biology__. "A set of brain areas were active in the chimps that have also been reported to be active when humans are communicating," William Hopkins, the lead researcher on the paper, told __The Scientist__. This means, said Hopkins, that the roots of human language may lie in the common ancestor of chimpanzees and humans. Hopkins, a psychologist at Agnes Scott College in Georgia, and colleagues used PET scans to map areas of activation in the brains of three captive chimps gesticulating and vocalizing towards human caretakers. Regions of the cerebral cortex, including parts of the inferior frontal gyrus (IFG), lit up in chimps gesticulating, raspberrying and grunting to signal their desire for food rewards placed outside their enclosures but still in view. In the human brain, the IFG contains Broca's area, which is a left-skewed asymmetrical region critical to the execution of language. Chimps' IFG activation approximates the position of Broca's area in humans, prompting Hopkins, who conducted the study at the linkurl:Yerkes National Primate Research;http://www.the-scientist.com/article/display/53392/ center in Atlanta, to refer to the area as the chimps' "Broca's homolog." linkurl:Claudio Cantalupo,;http://www.clemson.edu/psych/people/claudio_cantalupo.html a Clemson University neuropsychologist who was not involved with the study but collaborates with Hopkins, told __The Scientist__ that the results overturn the prevailing dogma that linkurl:brain asymmetry;http://www.the-scientist.com/article/display/14592/ is functionally significant only in human beings. "There are still people resisting this idea that non-human animals show evidence of brain asymmetry," Claudio said. While he and Hopkins have linkurl:shown anatomical asymmetry;http://www.ncbi.nlm.nih.gov/pubmed/11734839?ordinalpos=65&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum in chimps' brains, Hopkins' PET study identifies the functionality of this structural imbalance. There were, however, limitations to the study, Hopkins conceded. Firstly, three chimps is a relatively small sample size. "Obviously, with only three apes, there are some limitations on what you can generalize," Hopkins said. Still, he noted, the results strongly pointed to a discernable pattern in his test subjects. "Maybe with more apes, the picture might get a little more complicated." Another limitation was that it was impossible for Hopkins and his team to parse out the relative contributions of communicative gesturing and vocalizations in the brain activity patterns they saw. Hopkins said, though, that he is currently conducting research that ferrets out this distinction. It's still unclear whether similar patterns of brain activation occur in wild chimps communicating amongst themselves, linkurl:Katie Slocombe,;http://www.york.ac.uk/depts/psych/www/people/biogs/ks553.html a psychologist at the University of York told __The Scientist__. Slocombe said that data on wild chimp vocalization, which some researchers consider emotion-driven rather than truly communicative, would lend credence to Hopkins' suggestion that the neural circuitry necessary for language development may have been present in the common ancestor of chimps and humans. "I'm confident that in the future we will get evidence that there is communicative intent in their communications with other chimps," Slocombe said. "But we're a long, long way from knowing that."

Chimp's gestures share language roots

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