LOS ANGELES -- A unique opportunity to map and test the human brain has yielded new insights into two areas involved in producing and processing of language.
Speaking here today at the annual meeting of the Society for Neuroscience, David Corina, an assistant professor of psychology at the University of Washington, reported on the roles of two brain regions called Broca's area and the supramarginal gyrus. The findings came from a rare case, a deaf person called S.T. who uses American Sign Language. S.T. underwent a procedure called an awake cortical stimulation mapping, which allows assessment of language and motor functions at specific sites in the brain's left hemisphere.
Corina, a fluent signer, and an interdisciplinary team of UW researchers tested the subject and found that electrical stimulation of Broca's area and the supramarginal gyrus created repeated but different kinds of errors in S.T.'s ability to name objects. When Broca's area, which is located in the frontal lobe, was stimulated, S.T. had difficulty making clear hand shapes and specific movements associated with signs. Nonetheless, these sloppy signs resembled the target sign. Corina likens these errors to "mumbling" made in spoken languages. The subject made no effort to self-correct these lax or imperfect signs.
Stimulation of the supramarginal gyrus, a small area in the parietal
lobe, produced different kind of signing error. With stimulation, S.T. mixed up
word meanings and word forms. For example, when shown a picture of a pig and
asked to make the sign for it, S.T. made the sign for farm. The two signs are
very similar in hand shape, movement and spatial location to the sign pig in
American Sign Language, and would be distinct to skilled signer. Comparable
errors in English might be saying oyster instead of lobster or plane instead of
train. This type of error suggests that the supramarginal gyrus may be an area
of the brain important in the s
Contact: Joel Schwarz
University of Washington