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23 February 2010

Gestures, words the same in brain

New research suggests that the brain doesn't really care how it receives information - a waving hand up in the air to summon a waiter for "check please" works just fine.

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Humans speak; therefore, they're special.

At least that's what evolutionary language theorists would have people believe. Spoken language, they contend, is unique to the human brain, and that sets people apart from other primates.

But new research, co-authored by Patrick J. Gannon, a physical anthropologist and chairman of basic science education at Hofstra University School of Medicine, suggests that the brain doesn't really care how it receives information. A waving hand up in the air to summon a waiter for "check please" works just fine. The language areas of the brain - the highly evolved frontal and temporal lobes - process simple gestures with the same snippet of tissue that's used to hear the prose of Shakespeare, according to Gannon's study.

"It doesn't matter to the brain what channel the information comes in on or goes out," said Gannon, who is also an evolutionary neurobiologist.

Great apes can process language

A decade ago, he and his colleagues showed that great apes have the same brain architecture necessary for language as humans have. That surprised many at the time, despite whole fields of research showing that great apes can learn to understand complex human language. But the very fact that modern primates - chimps, gorillas, bonobos and orangutans - don't banter back and forth verbally was evidence to many language theorists that humans had evolved a more finely tuned brain.

Gannon wanted to challenge the theory with scientific proof that gestures convey the same complex messages as verbal language, and that the brain processes both forms of communication the same way.

The study

Working with Dr Allen R. Braun, chief of the language section at the US National Institute on Deafness and Other Communication Disorders, Gannon designed an experiment to watch the brain as it responds to spoken language and to common symbolic gestures - putting a finger to the lips to quiet kids or denoting peace with forked fingers.

They recruited 20 English-speaking volunteers, a mix of men and women, to watch video clips of an actress gesturing or speaking the phrases that the gestures indicate. An MRI brain scan snapped pictures of the brain responding to the two seemingly different forms of communication. For comparison, the volunteers also watched clips of meaningless hand and arm movements and a jumble of half-words that made no sense.

The goal was to see what areas of the brain were used during these different forms of communication.

Using the same neural tissue

What they found was that it was the same neural tissue. The experiments revealed that the frontal and posterior temporal areas were activated under both conditions, what the researchers describe as compelling proof that the brain can receive information in any form - a gesture, a picture, words on a page, a sound or an object - and that these regions of the brain will process it. The findings were published recently in the Proceedings of the National Academy of Sciences.

"We support multi-sensory integration," Gannon said. "There is nothing special about auditory or spoken language. This tells us about the evolutionary depth of our common system and that gestures were the beginning of language."

Many disagree

Not all agree, though, with many language theorists holding fast to the idea that spoken language evolved independently of gestures. To counter that, Gannon asked: "Why would a part of the brain do the same thing regardless of the type of information it receives?"

It makes perfect sense, said William D. Hopkins, an associate professor of psychology at Agnes Scott College and a research scientist at Yerkes National Primate Research Centre. "The whole system is linked to pairing symbolic information to referential information in the environment," he said. "It is interesting. These areas are there to help make connections."

The finding "evens the playing field when thinking about the development of language," Hopkins said. "The brain is not making a distinction between gestures and verbal language. It's possible that speech co-opted the neural networks that underlie gestures."

Gesturing in chimps

Hopkins and his colleagues, who study the evolution of gesturing in chimps, have found that chimps, like humans, have a preference for using their right hand. In chimps, this right-handedness is obvious only when they're communicating information to either another chimp or a human. And brain scans of the chimps, taken when they were using their right hand to communicate, identified activation of the same regions that Gannon's research identified.

The implications of all this? Some experts say that Gannon's finding could help researchers and clinicians understand and treat brain conditions such as aphasia, which wipes out people's ability to comprehend information and express themselves verbally, and autism, which involves a complex array of language-based problems. Others think it might be possible to strengthen these brain connections or open new doors for communication with gestures. – (Jamie Talan/HealthDay News, February 2010)

 
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