It is also possible for
deaf individuals to develop Broca's
aphasia, even if their first language is
sign language. Psycholinguists Howard Poizner and Ursula Bellugi, together with
linguist Edward Klima, conducted interviews with native speakers of
ASL who had suffered
brain damage, usually as a result of a
stroke.
Here is an excerpt from an interview with a deaf woman with damage to her left hemisphere. Signed words are in capital letters, fingerspelled words are letters separated by hyphens.
Examiner: What else happened?
Gail: CAR... DRIVE... BROTHER... DRIVE... I... S-T-A-D... <Attempts to gesture stand up.>
E: You stood up?
G: YES... I... DRIVE... <Attempts to gesture goodbye.>
E: Wave goodbye?
G: YES... BROTHER... DRIVE... DUNNO... <Attempts to wave goodbye.>
E: Your brother was driving?
G: YES... BACK... DRIVE... BROTHER... MAN... MAMA... STAY... BROTHER... DRIVE.
E: Were you in the car?
G: YES.
E: Or outside?
G: NO.
E: In the car.
G: YES.
E: You were standing up with your mother?
G: NO... BROTHER... DRIVE... <Points in back> DEAF BROTHER... I...
E: Your brother didn't know you were in the car?
G: YES.
E: Your brother was driving and saw you in the back seat?
G: YES, YES. <Laughs.>
There are similarities between Gail's language disturbance in ASL and those of English-speaking individuals with Broca's aphasia. While the left hemisphere is specialized for language processing, the right hemisphere is specialized for visual and spatial processing. Because ASL is a language involving visual-spatial processing, it was unknown before the Poizner-Bellugi-Klima experiments what would happen to indiviudals with such brain damage. Gail's ASL lacked all the inflection and grammatical features of normal ASL, and she did not use ASL classifiers just as brain damaged English-speaking individuals often do not use pronouns. Neurological testing confirmed that Gail had suffered damage to the Broca's area, and other patients showed similar results.
Source
Lane, H., Hoffmeister, R. & Bahan, B. A Journey into the DEAF-WORLD. San Diego: DawnSign Press, 1996.