Interarticulator co-ordination in Deaf signers with Parkinson's disease

Motor control deficits in signers with Parkinson's disease (PD) were examin ed through analysis of their production of American Sign Language (ASL) fin gerspelling, which is sequential and rapid motor behavior that has theoreti cal models of its underlying structure. Free conversation of two Deaf signe rs with PD and two Deaf control signers was analysed. Iii addition, scripte d productions of one control signer were also analysed and directly compare d to the same productions by the signers with PD. A featural analysis of AS L fingerspelling and a frame-by-frame analysis of multiple articulator move ments were used to examine the fingerspelled productions. On the basis of t he featural analysis, the signers with PD showed a variety of error pattern s, all of which reflected attempts to reduce the motoric demands of coartic ulation and thereby facilitate ease of articulation. Signers with PD either held individual segments in a fingerspelling sequence for a long time (seg mentation), blended adjacent segments into a single segment (sequential ble nding), or broke handshapes down sequentially into their component features (featural unraveling). The results of both the featural analysis and the f rame-by-frame analysts show that the PD signers have difficulty co-ordinati ng the movements of independent articulators in complex sequences. For exam ple, the movements of independent articulators for fingerspelling (the thum b, fingers, and wrist) were markedly farther apart in time and more variabl e for the signers with PD. In addition, the signers with PD used fewer wris t movements while fingerspelling. Such deficits are consistent with claims that patients with PD are impaired in their ability to use ongoing sensorim otor information to program multi-articulator movements. (C) 1999 Elsevier Science Ltd. All rights reserved.