APHASIC AND PARKINSONIAN SIGNING - DIFFERENCES IN PHONOLOGICAL DISRUPTION

Since movements of the articulators in sign, unlike in speech, are dir ectly observable, we can investigate signing not only as linguistic be havior but also as motor behavior and directly contrast linguistic-rep resentational and motor-execution disorders of signing. We compared th e temporal sequencing characteristics (duration of segments, pausing, periods of change in handshape posture), intactness of distinctive fea tures, and correct use of prosodic templates in three pairs of signers -two Deaf aphasic signers with posterior damage in the left hemisphere , two signers with Parkinson's disease, and two gender- and age-matche d control signers. With respect to distinctive features, the aphasic s igners exhibited selection errors in the American Sign Language (ASL) distinctive features system, while the Parkinsonian signers showed an intact distinctive feature inventory, but with disturbances in executi ng these features. The Parkinsonian signers, unlike the aphasic and co ntrol signers, showed marked disturbances in the temporal organization and coordination of what we argue are the two subsystems of the ASL s ign stream-handshape and movement. The findings demonstrate a phonetic deficit in Parkinsonian signers, in contrast with aphasic signers who showed a disruption in the underlying representation and syllabificat ion processes in the language. (C) 1995 Academic Press, Inc.