Single
Limb Performance Following Contralateral Bimanual Limb Training
Jamie
Kaye Burgess, Rachel Bareither, and James L. Patton,
Member, IEEE
IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION
ENGINEERING, VOL. 15, NO. 3, SEPTEMBER 2007 p.347-355
Abstract—Recent studies on intermanual transfer of reaching movements
suggest that this transfer is conducted over an “extrinsic” coordinate system.
We hypothesize that training reaching movements in a force field with both
hands at the same time, in the same position (bimanual grip) will be more
beneficial in promoting transfer of the learned skill to the dominant hand than
training the unimpaired limb on the same movements in the same force field since
the representation of the movement should be invariant of the limb. However,
unlike intermanual transfer, bimanual transfer has the potential to involve
infinite number of actuator combinations, or joint configurations, interfering
with consistent transfer. The ef- ficacy
of this method of transfer has implications for people with hemiparesis since
the less-affected arm could potentially “instruct” the more-affected arm how to
move. Here, we report on an experiment that evaluates and compares the skill
transfer between limbs in a reaching task: 1) intermanual transfer (from the
nondominant to the dominant hand) and 2) bimanual transfer (from a bimanual grip
to the dominant hand) with healthy subjects.We used two
methods from which to judge the transfer: performance in the presence of the
force field or by errors made during “catch trials” when the forces were
unexpectedly removed as subjects changed hands (known as after effects of
adaptation).We found only a small amount of transfer (20% of that seen in the
practiced limb) with both types of training, and surprisingly there was no
significant difference in the movement accuracy between these two training methods.
Moreover, the direction of the after effects supports the assertion
that the nervous system generalizes these movements in an extrinsic coordinate
system. Accordingly, the limb must experience the dynamics singularly in order
to develop an internal model.
Index Terms—Adaptation, force field, human motor control, internal model.