With the help of a novel technique, scientists at Yerkes National Primate Research Centre, Emory University, have identified a language feature distinctive to human brain that may provide an insight into the evolution of human language.
While using the Diffusion Tensor Imaging (DTI), a non-invasive imaging technique, the researchers compared the human brain structures with chimpanzees.
They analysed the arcuate fasciculus, a pathway that connects brain regions involved in human language, such as Broca's area in the frontal lobe and Wernicke's area in the temporal lobe.
While comparing the brain structures of humans, rhesus macaques and chimpanzees, the team found that the human arcuate fasiculus differed from that of the rhesus macaques and chimpanzees in having a much larger and more widespread projection to areas in the middle temporal lobe, outside of the classical Wernicke's area.
"We know from previous functional imaging studies that the middle temporal lobe is involved with analysing the meanings of words," Nature quoted James Rilling, lead researcher, as saying.
"In humans, it seems the brain not only evolved larger language regions but also a network of fibres to connect those regions, which supports humans' superior language capabilities," he added.
"This is a landmark," said Todd Preuss, a Yerkes researcher and study's co-author. †
"Until DTI was developed, scientists lacked non-invasive methods to study brain connectivity directly. We couldn't study the connections of the human brain, nor determine how humans resemble or differ from other animals.
"DTI now makes it possible to understand how evolution changed the wiring of the human brain to enable us to think, act and speak like humans," Preuss added.
The study will be published in the online version of Nature Neuroscience.