The Journal of Neuroscience, March 15, 2003, 23(6):2383
Coarticulation in Fluent Fingerspelling
Thomas E.
Jerde1, 2,
John F.
Soechting1, and
Martha
Flanders1
1 Department of Neuroscience, University of Minnesota,
Minneapolis, Minnesota 55455, and 2 Department of
Neuroscience, Brown University, Providence, Rhode Island 02912
In speech, the phenomenon of coarticulation (differentiation of
phoneme production depending on the preceding or following phonemes)
suggests an organization of movement sequences that is not strictly
serial. In the skeletal motor system, however, evidence for comparable
fluency has been lacking. Thus the present study was designed to
quantify coarticulation in the hand movement sequences of sign language
interpreters engaged in fingerspelling. Records of 17 measured joint
angles were subjected to discriminant and correlation analyses to
determine to what extent and in what manner the hand shape for a
particular letter was influenced by the hand shapes for the preceding
or the following letters. Substantial evidence of coarticulation was
found, revealing both forward and reverse influences across letters.
These influences could be further categorized as assimilation (tending
to reduce the differences between sequential hand shapes) or
dissimilation (tending to emphasize the differences between sequential
hand shapes). The proximal interphalangeal (PIP) joints of the index
and middle fingers tended to show dissimilation, whereas at the same
time (i.e., during the spelling of the same letters) the joints of the
wrist and thumb tended to show assimilation. The index and middle
finger PIP joints have been shown previously to be among the
most important joints for computer recognition of the 26 letter shapes,
and therefore the dissimilation may have served to enhance visual
discrimination. The simultaneous occurrence of dissimilation in some
joints and assimilation in others demonstrates an unprecedented level
of parallel control of individual joint rotations in an essentially serial task.
Key words:
sensorimotor integration; movement sequences; fingerspelling; sign language; hand movement; coarticulation
Copyright © 2003 Society for Neuroscience 0270-6474/03/2362383-11$05.00/0
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