The Journal of Neuroscience, March 1, 2003, 23(5):1981
Sensorimotor Memory For Fingertip Forces: Evidence For A
Task-Independent Motor Memory
Barbara M.
Quaney,
Diane L.
Rotella,
Clayton
Peterson, and
Kelly J.
Cole
Department of Exercise Science, The University of Iowa, Iowa City,
Iowa 52241
When repetitively lifting an object with randomly varying
mechanical properties, the fingertip forces reflect the previous lift.
We examined the specificity of this "sensorimotor memory" by
observing the effects of an isolated pinch on the subsequent lift of a
known object. In this case, the pinch force was unrelated to the
fingertip forces necessary to grip the object efficiently. The peak
grip force used to lift the test object (4 N weight) depended on the
preceding task. Compared with repetitively lifting the 4 N test object,
the peak grip force was 2 N greater when a lift of the same object was
preceded by a lift in which a hidden mass was attached to the object to
increase the weight to 8 N. This 2 N increase in grip force also
occurred when subjects lifted the 4 N test object after pinching a
force transducer with a force of 8 N. Thus, similar grip forces were
stored in sensorimotor memory for both tasks, and reflected subjects'
use of 7.9 ± 1.1 N to lift the 8 N object. Similar effects
occurred when the preceding pinch or lift was performed with the
opposite hand. The peak lift force was unaffected by the isolated
pinch, suggesting that a generalized increase in fingertip and limb
forces did not occur. We conclude that the sensorimotor memory is not
specific for lifting an object. It is doubtful that this particular
memory stores the physical properties of objects or reflects a forward
internal model for predictively controlling fingertip forces.
Key words:
grip force; memory; prediction; internal model; grasping; feedforward control
Copyright © 2003 Society for Neuroscience 0270-6474/03/2351981-06$05.00/0