Аннотация
In manual action, the relationship between a given motorcommandand
the ensuing movement depends on the dynamics of both the arm
and hand-held objects. Skilled performance relies on the brain learning
both these dynamics, and previous studies have examined how
people adapt to novel loads applied to either the hand or the arm.
In this study, we ask whether these different kinds of load are
represented independently as a result of changes in cutaneous feedback
and handarm coordination. We used a robotic apparatus that
could either apply forces to an object held in the subjects hand
or directly to the segments of the arm. We tested whether subjects
could
retain learning of a force field applied to the hand after subsequently
experiencing the opposing field applied to the arm (or vice versa),
or
whether retrograde interference would be observed. In separate experiments,
we used force fields and torque fields that were linearly
related to either hand or joint velocities, respectively. Our finding
of complete interference between opposing fields suggests that loads
applied to the arm and hand are not represented independently by the
sensorimotor system. This interference occurred despite markedly
different cutaneous inputs that were directly related to the movement
task. This result suggests that the brain represents dynamics
independently of these sensory inputs. In addition, we found that
the rate at which subjects adapted to a given force field, specified
either
in hand or joint coordinates, was independent of whether the forces
were applied to the hand or arm segments.
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