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American Sign Language: Neurolinguistics

Frank Medellin
November 16, 2002

Neurolinguistics of American Sign Language

I have had a long interest in why some people have difficulty with one aspect of language processing, including sign language, whether is be receptive or expressive skills. Having lived in England, Italy, and Hawaii I had difficulty comprehending the spoken languages, but no problems picking up a British accent within 6 months of living in England, speaking Italian, or speaking Pidgin English in Hawaii. The same is true for my signing proficiency. I sign well but have difficulties comprehending sign language, especially in an interpreting situation where I am required to simultaneously voice the message. Is there a reason for this? Is this a ‘left brain, right brain’ thing? I was hoping my brief research could give me an insight into the topic.

The information is based partly on the main article I selected, Sign Language In The Brain ( Hickok, Bellugi, Kilma, 2001). The study was conducted on the visual-spatial signals (sign language) to determine whether the brain regions that interpret and generate sign language are the same ones involved in spoken language. One could hypothesize that sign language would be supported by systems in the brain’s right hemisphere because signs are visual-spatial signs, therefore not engaging the left hemisphere where spoken language is processed. Most research on language had been based on the study of spoken language. In 1861 French neurologist, Paul Broca discovered that patients who could understand spoken language but had difficulty speaking tended to have damage to a part of the brain’s left hemisphere, now known as Broca’s area. In 1874 German physician, Carl Wernicke found that patients with fluent speech but severe comprehension problems typically had damage to another part of the left hemisphere, which was called Wernicke’s area. Damage to the brain’s right hemisphere rarely results in language disruptions, or aphasias. 

Over the past two decades, this study examined groups of deaf signers who suffered damage either to the right or left hemisphere of their brains. By evaluating their proficiency at understanding and producing signs, the study set out to determine whether the brain regions that interpret and generate sign language are the same ones involved in spoken language. Did deaf signers with brain damage have damage to Broca’s or Wernicke’s areas? The results supported the theory. Patient’s disorganized signing and lack of comprehension were similar to hearing patients with Wernicke’s aphasia. Another patient had severe production problems, but comprehended sign language perfectly. This parallels symptoms of Broca’s aphasia. The deaf signer with comprehension problems had damage that included Wernicke’s area and the patient who had production problems had damage that involved Broca’s area. Further studies backed their findings. The findings suggest that the brain’s left hemisphere is dominant for sign language just as it is for speech. Signers with damage to the right hemisphere were fluent and accurate in the production of sign thus hindering the hypothesis that sign language would be supported by the right hemisphere.

A very interesting point brought up through another study is the division of visual-spatial abilities between the two hemispheres—a local level in the left hemisphere 
dominant for producing and comprehending signs and signed sentences, and a global level in the right hemisphere dominant for establishing and maintaining a coherent discourse in sign language. The information from this study made me slightly aware that I may have some dysfunction to my left hemisphere, or Wernicke’s area. It could be a case of ‘left brain, right brain’. More interestingly, it could be a topic for research in a Doctoral program, an in-depth study into sign language processing in the brains’ left hemisphere of educators/interpreters for the Deaf.


Reference:


Anderson, S.W., Damasio, H., Damasio, A.R., Bellugi, U., Tranel, A.P., Brandt, J.P. & O’Grady-Batch, L. (1990). Sign language acquisition following left hemisphere damage and aphasia. Journal of Clinical and Experimental Neuropsychology, 12(1), 47. Retrieved November 5, 2002.

Bellugi, U. (1983). Language structure and language breakdown in American Sign Language. Studdert-Kennedy (Ed.), Psychobiology of language (pp. 152-176). Cambridge, MA: MIT Press. Retrieved November 15, 2002.

Bellugi, U., & Studdert-Kennedy, M. (Eds.). (1980). Signed and spoken language: Biological constraints on linguistic form. Dahlem Konferenzen. Weinheim/Deerfield Beach, FL: Verlag Chemie. Retrieved November 1, 2002.

Hickok, G., Bellugi, U., & Kilma, E., June 2001, Sign Language In The Brain. Scientific American. Retrieved October 12, 2002.

 

 


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