Columbia, Mount Sinai Scientists Find Region That Controls Language Identical in Both Species; Chimps May Use Gestures to Communicate
Researchers at Mount Sinai School of Medicine, Columbia Universityand the National Institutes of Health have found that a region of the brainthought to control language is proportionately the same size in humans andchimpanzees, disproving a theory that the brain section was enlarged onlyin humans.
The discovery, reported in the Jan. 9 issue of the journal Science,throws into question the role of the planum temporale, a part of thebrain's temporal cortex that is located beneath the parietal cortex. Theplanum temporale of the left hemisphere is normally larger than in theright hemisphere in humans, but 94 percent of the chimpanzee brains studieddemonstrated the same asymmetry.
Could the research result be interpreted to mean that chimpanzeeshave some kind of language? "I don't think they have a language, but I doagree that they have some kind of communication system that might be morecomplex than we have heretofore thought," said Ralph Holloway, professor ofanthropology at Columbia and co-author of the Science paper. He believeschimps may converse using a sophisticated array of facial, body and handgestures, perhaps augmented with grunting or other vocalizations.
Patrick Gannon, assistant professor and director of the PaleoneurologyResearch Laboratory in the Department of Otolaryngology at Mount Sinai,first suspected that chimpanzee brains might show the same asymmetry asthose ofhumans. He sought the collaboration of Professor Holloway, who thenassisted in measuring the planum temporale, which is not an obviousanatomical feature, on his collection of 18 chimpanzee brains. TheColumbia anthropologist conducts comparative neuroanatomical studies on thechimpanzee brains in order to better understand evolution of the humanbrain.
The research finding contradicts a long-standing scientific theorythat only humans displayed the left-side brain enlargement.Nineteenth-century neurologist Carl Wernicke had noticed that patients withbrain lesions of the posterior temporal lobe and parietal lobe - the samearea studied by the Mount Sinai and Columbia researchers - could producelanguage but couldn't understand it. That region of the temporal cortex,also known as Wernicke's area, was thought to control languagecomprehension, but only in humans.
"After 100 years of people doing comparative brain studies, youassume that the dogma is true. It came as quite a shock to discover thatthe chimpanzee brains did show the same asymmetry as humans," Dr. Gannonsaid.
He first theorized that the received wisdom might not be true whenhe conducted magnetic resonance imaging studies of chimpanzee brains in anNIH study and noticed the discrepancy between the brain hemispheres.
The authors of the paper, who also included Allen Braun of theNational Institute on Deafness and Other Communication Disorders at NIH,proposed several possible interpretations of the work, in addition to thepossibility of chimp communication. If both chimps and humans have anenlarged planum temporale, their common ancestor probably had the featureas well, though the brain region may not have acquired its languagefunctions until humans split off from other primates 6 to 8 million yearsago. Finally, it may well be that the planum temporale is not involved inlanguage in either chimps or humans.
The research was supported by the National Science Foundation, theNational Institute on Deafness and Other Communication Disorders of theNational Institutes of Health and the Department of Otolaryngology and theGrabscheid Voice Center at Mount Sinai.
Materials provided by Columbia University. Note: Content may be edited for style and length.
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