Rapid adaptation to Coriolis force perturbations of arm trajectory
J. R. Lackner and P. Dizio Brandeis University, Waltham, Massachusetts 02254-9110. 1. Forward reaching movements made during body rotation generate tangential Coriolis forces that are proportional to the cross product of the angular velocity of rotation and the linear velocity of the arm. Coriolis f...
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Veröffentlicht in: | Journal of neurophysiology 1994-07, Vol.72 (1), p.299-313 |
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Zusammenfassung: | J. R. Lackner and P. Dizio
Brandeis University, Waltham, Massachusetts 02254-9110.
1. Forward reaching movements made during body rotation generate tangential
Coriolis forces that are proportional to the cross product of the angular
velocity of rotation and the linear velocity of the arm. Coriolis forces
are inertial forces that do not involve mechanical contact. Virtually no
constant centrifugal forces will be present in the background when motion
of the arm generates transient Coriolis forces if the radius of body
rotation is small. 2. We measured the trajectories of arm movements made in
darkness to a visual target that was extinguished as movement began. The
reaching movements were made prerotation, during rotation at 10 rpm in a
fully enclosed rotating room, and postrotation. During testing the subject
was seated at the center of the room and pointed radially. Neither visual
nor tactile feedback about movement accuracy was present. 3. In experiment
1, subjects reached at a fast or slow rate and their hands made contact
with a horizontal surface at the end of the reach. Their initial perrotary
movements were highly significantly deviated relative to prerotation in
both trajectories and end-points in the direction of the transient Coriolis
forces that had been generated during the reaches. Despite the absence of
visual and tactile feedback about reaching accuracy, all subjects rapidly
regained straight movement trajectories and accurate endpoints.
Postrotation, transient errors of opposite sign were present for both
trajectories and endpoints. 4. In a second experiment the conditions were
identical except that subjects pointed just above the location of the
extinguished target so that no surface contact was involved. All subjects
showed significant initial perrotation deviations of trajectories and
endpoints in the direction of the transient Coriolis forces. With repeated
reaches the trajectories, as viewed from above, again became straight, but
there was only partial restoration of endpoint accuracy, so that subjects
reached in a straight line to the wrong place. Aftereffects of opposite
sign were transiently present in the postrotary movements. 5. These
observations fail to support current equilibrium point models, both alpha
and lambda, of movement control. Such theories would not predict endpoint
errors under our experimental conditions, in which the Coriolis force is
absent at the beginning and end of a movement. Our results indicate that
detailed |
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ISSN: | 0022-3077 1522-1598 |
DOI: | 10.1152/jn.1994.72.1.299 |