Monday, 24 March 2008

Brain Area Critical for Chimpanzee Communication Corresponds to Area Responsible for Human Communication

Findings suggest the neurobiological foundations of human language may have been present in the common ancestor of modern humans and chimpanzees.

Researchers at the Yerkes National Primate Research Center have found the area in the chimpanzee brain involved in the production of chimpanzee manual gestures and vocalizations is similar to what is known as Broca’s area in the human brain. The study, available in the online edition of Current Biology, is the first to directly link chimpanzee and human brain areas associated with communicative behaviors, suggesting chimpanzee communication is not only more complicated than previously thought, but also that the neurobiological foundations of human language may have been present in the common ancestor of modern humans and chimpanzees.In the human brain, Broca’s area is one of several critical regions associated with gestures and speech. Human functional imaging studies have shown significant patterns of activity in this area during language-related tasks. Lead researcher Jared Taglialatela, PhD, set out to determine if chimpanzees would show comparable patterns of activity in an area of the brain anatomically similar to the Broca’s area.“We were interested in determining the neurobiological underpinnings of chimpanzee communication, as a number of behavioral studies indicate chimpanzees intentionally produce manual gestures, as well as some types of vocal signals, to communicate with humans,” said Taglialatela. For the study, three chimpanzees each participated in two different tasks. For the communication task, a researcher sat outside the chimpanzees’ home enclosures with pieces of food. After a set period of time, the researcher took the food and left the chimpanzee area. When the researcher was present, the chimpanzees produced gestures and vocalizations to request the food. For the baseline task, the researcher again approached the enclosures with food, but this time, chimpanzees received small stones to exchange for pieces of food. After returning a fixed number of stones, each chimpanzee was rewarded with a small piece of food. “The chimpanzees were not communicating with the researcher in this task; they were simply returning stones,” said Taglialatela. “We included this task to make sure we really were looking at neural activity associated with communicative signaling and not simply normal motor behaviors,” he continued.During each task, researchers used positron emission topography (PET) to monitor chimpanzee brain activity. Both tasks showed significant brain activity, but researchers found considerably greater levels of activity during the communication task as compared to baseline in an area of the brain similar to Broca’s area. Taglialatela said, “One interpretation of our finding is that chimpanzees have, in essence, a language-ready brain. Our results support that apes use this brain area when producing signals that are part of their communicative repertoire.”

Source :The Yerkes National Primate Research Center of Emory University 2008.

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