New study finds speech-like brain activity in deaf signers
A new study challenges the prevailing notion that speech and sound are essential to human language.
Montreal, December 5, 2000. A new study challenges the prevailing notion that speech and sound are essential to human language. Researchers have found that rather than being born exclusively to speak, the human brain has the ability to make sense of highly specific patterns found in all human language, spoken or signed.
Drs Laura Ann Petitto of the Department of Psychology and Robert Zatorre of the Montreal Neurological Institute, McGill University, conducted a Positron Emission Tomography (PET) study to compare patterns of blood flow in the brains of deaf and hearing individuals in response to signed (American Sign Language or Langue des Signes Québécoise) and spoken language. They report that signing deaf people processed very specific parts of natural language (like words and parts of words) at the same highly specific brain sites as hearing people do with speech. These regions of the brain have, for more than 100 years, been regarded as exclusively processing sound. "Our results have exciting implications since deaf people cannot hear speech and their signed languages have evolved on the hands, in the absence of sound," says Dr Petitto.
Their discovery led Drs Petitto and Zatorre to offer a new account of the brain and language. Rather than being programmed exclusively to talk and to hear speech, areas of the brain viewed as specialized for sound may be tuned to highly specific patterns important to the structure of natural language. The researchers expect that the new findings will contribute to our understanding of the brains impressive plasticity in early life, as well as to better understand those areas that are already specialized.
These findings are published today in the highly cited scientific journal Proceedings of the National Academy of Sciences in an article entitled Speech-like cerebral activity in profoundly deaf people processing signed languages: Implications for the neural basis of human language by L.A. Petitto, R.J. Zatorre, E.J. Nikelski, K. Gauna, D. Dostie, and A.C. Evans. Further information on this study (including QuickTime movies of the deaf signer signing samples of the visual stimuli) is available on the web.
Funding for this research was made possible by the generous support of the Natural Sciences and Engineering Research Council of Canada, Medical Research Council of Canada/Canadian Institutes for Health Research, and The McDonnell-Pew Centre for Cognitive Neuroscience, Brain Imaging Centre of the Montreal Neurological Institute.