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Uniqueness in human brain’s language zone

March 24, 2008
Courtesy Emory University
and World Science staff

Re­search­ers have iden­ti­fied a lan­guage fea­ture that they say is un­ique to the hu­man brain and is shed­ding light on how hu­man lan­guage evolved. Hu­man brain cells have more com­plex in­ter­con­nec­tions in and around brain ar­eas linked to lan­guage, the sci­en­t­ists ex­plain.

Shad­ed are hu­man brain re­gions im­pli­cat­ed in lan­guage: the so-called Bro­ca's and Wer­nick­e's ar­eas. (Im­age cour­te­sy NIDCD)


The study marks the first use of dif­fu­sion ten­sor im­ag­ing, a non-invasive im­ag­ing tech­nique, to com­pare hu­man brain struc­tures to those of chim­panzees, our clos­est liv­ing rel­a­tive.

The re­search­ers at Em­o­ry Uni­ver­s­ity’s Yer­kes Na­tional Pri­mate Re­search Cen­ter in Geor­gia stud­ied the ar­cu­ate fas­cic­u­lus, a path­way that con­nects brain re­gions known to be in­volved in hu­man lan­guage. 

These parts of the brain in­clude the so-called Bro­ca’s ar­ea in the front­al lobe, to­ward the front of the head, and Wer­nick­e’s ar­ea in the tem­po­ral lobe, at the side of the head. 

The re­search­ers com­pared the size and tra­jec­to­ry of the ar­cu­ate fas­cic­u­lus in hu­mans, rhe­sus macaques and chim­panzees. The hu­man ver­sion has “much larg­er and more wide­spread pro­jec­tion to ar­eas in the mid­dle tem­po­ral lobe, out­side of the clas­si­cal Wer­nick­e’s ar­ea,” said James Rilling of Yer­kes, who led the stu­dy.

“We know from pre­vi­ous func­tion­al im­ag­ing stud­ies that the mid­dle tem­po­ral lobe is in­volved with an­a­lyz­ing the mean­ings of words. In hu­mans, it seems the brain not only evolved larg­er lan­guage re­gions but al­so a net­work of fibers to con­nect those re­gions, which sup­ports hu­mans’ su­pe­ri­or lan­guage ca­pa­bil­i­ties.” The study is pub­lished on­line in the re­search jour­nal Na­ture Neu­ro­sci­ence.


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Researchers have identified a language feature that they say is unique to the human brain and is shedding light on how human language evolved. Human brain cells have more complex interconnections in and around brain areas linked to language, the researchers explain. The study marks the first use of diffusion tensor imaging, a non-invasive imaging technique, to compare human brain structures to those of chimpanzees, our closest living relative. The study will be published in the online version of Nature Neuroscience. The researchers at Emory University’s Yerkes National Primate Research Center in Georgia colleagues studied the arcuate fasciculus, a pathway that connects brain regions known to be involved in human language. These parts of the brain include the so-called Broca’s area in the frontal lobe, toward the front of the head, and Wernicke’s area in the temporal lobe, at the side of the head. The researchers compared the size and trajectory of the arcuate fasciculus in humans, rhesus macaques and chimpanzees. The human version has “much larger and more widespread projection to areas in the middle temporal lobe, outside of the classical Wernicke’s area,” said James Rilling of Yerkes, who led the study. “We know from previous functional imaging studies that the middle temporal lobe is involved with analyzing the meanings of words. In humans, it seems the brain not only evolved larger language regions but also a network of fibers to connect those regions, which supports humans’ superior language capabilities.”