Words, Gestures Are Translated By Same Brain Regions
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- Date: Tue, 17 Nov 2009 12:07:36 -0800 (PST)
http://www.scienced aily.com/ releases/ 2009/11/09110917 3412.htm
Words, Gestures Are Translated By Same Brain Regions
ScienceDaily (Nov. 10, 2009) — Your ability to make sense of
Groucho's words and Harpo's pantomimes in an old Marx Brothers movie
takes place in the same regions of your brain, says new research
funded by the National Institute on Deafness and Other Communication
Disorders (NIDCD), one of the National Institutes of Health.
In a study published in this week's Early Edition of Proceedings of
the National Academy of Sciences (PNAS), researchers have shown that
the brain regions that have long been recognized as a center in which
spoken or written words are decoded are also important in interpreting
wordless gestures. The findings suggest that these brain regions may
play a much broader role in the interpretation of symbols than
researchers have thought and, for this reason, could be the
evolutionary starting point from which language originated.
"In babies, the ability to communicate through gestures precedes
spoken language, and you can predict a child's language skills based
on the repertoire of his or her gestures during those early months,"
said James F. Battey, Jr., M.D., Ph.D., director of the NIDCD. "These
findings not only provide compelling evidence regarding where language
may have come from, they help explain the interplay that exists
between language and gesture as children develop their language
skills."
Scientists have known that sign language is largely processed in the
same regions of the brain as spoken language. These regions include
the inferior frontal gyrus, or Broca's area, in the front left side of
the brain, and the posterior temporal region, commonly referred to as
Wernicke's area, toward the back left side of the brain. It isn't
surprising that signed and spoken language activate the same brain
regions, because sign language operates in the same way as spoken
language does -- with its own vocabulary and rules of grammar.
In this study, NIDCD researchers, in collaboration with scientists
from Hofstra University School of Medicine, Hempstead, N.Y., and San
Diego State University, wanted to find out if non-language- related
gestures -- the hand and body movements we use that convey meaning on
their own, without having to be translated into specific words or
phrases -- are processed in the same regions of the brain as language
is. Two types of gestures were considered for the study: pantomimes,
which mimic objects or actions, such as unscrewing a jar or juggling
balls, and emblems, which are commonly used in social interactions and
which signify abstract, usually more emotionally charged concepts than
pantomimes. Examples include a hand sweeping across the forehead to
indicate "it's hot in here!" or a finger to the lips to signify "be
quiet."
While inside a functional MRI machine, 20 healthy, English-speaking
volunteers -- nine males and 11 females -- watched video clips of a
person either acting out one of the two gesture types or voicing the
phrases that the gestures represent. As controls, volunteers also
watched clips of the person using meaningless gestures or speaking
pseudowords that had been chopped up and randomly reorganized so the
brain would not interpret them as language. Volunteers watched 60
video clips for each of the six stimuli, with the clips presented in
45-second time blocks at a rate of 15 clips per block. A mirror
attached to the head enabled the volunteer to watch the video
projected on the scanner room wall. The scientists then measured brain
activity for each of the stimuli and looked for similarities and
differences as well as any communication occurring between individual
parts of the brain.
The researchers found that for the gesture and spoken language
stimuli, the brain was highly activated in the inferior frontal and
posterior temporal areas, the long-recognized language regions of the
brain.
"If gesture and language were not processed by the same system, you'd
have spoken language activating the inferior frontal and posterior
temporal areas, and gestures activating other parts of the brain,"
said Allen Braun, M.D., senior author on the paper, "But in fact we
found virtual overlap."
Current thinking in the study of language is that, like a smart search
engine that pops up the most suitable Web site at the top of its
search results, the posterior temporal region serves as a storehouse
of words from which the inferior frontal gyrus selects the most
appropriate match. The researchers suggest that, rather than being
limited to deciphering words alone, these regions may be able to apply
meaning to any incoming symbols, be they words, gestures, images,
sounds, or objects. According to Dr. Braun, these regions also may
present a clue into how language evolved.
"Our results fit a longstanding theory which says that the common
ancestor of humans and apes communicated through meaningful gestures
and, over time, the brain regions that processed gestures became
adapted for using words," he said. "If the theory is correct, our
language areas may actually be the remnant of this ancient
communication system, one that continues to process gesture as well as
language in the human brain."
Dr. Braun adds that developing a better understanding of the brain
systems that support gestures and words may help in the treatment of
some patients with aphasia, a disorder that hinders a person's ability
to produce or understand language.
.
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