Is Interlimb Transfer of Force-Field Adaptation a Cognitive Response to the Sudden Introduction of Load?

Abstract

Recently, Criscimagna-Hemminger et al. (2003) reported a pattern of generalization of force-field adaptation between arms that differs from the pattern that occurs across different configurations of the same arm. Although the intralimb pattern of generalization points to an intrinsic encoding of dynamics, the interlimb transfer described by these authors indicates that information about force is represented in a frame of reference external to the body. In the present study, subjects adapted to a viscous curl-field in two experimental conditions. In one condition, the field was introduced suddenly and produced clear deviations in hand paths; in the second condition, the field was introduced gradually so that at no point during the adaptation process could subjects observe or did they have to correct for a substantial kinematic error. In the first case, a pattern of interlimb transfer consistent with Criscimagna-Hemminger et al. (2003) was observed, whereas no transfer of learning between limbs occurred in the second condition. The findings suggest that there is limited transfer of fine compensatory-force adjustment between limbs. Transfer, when it does occur, may be primarily the result of a cognitive strategy that arises as a result of the sudden introduction of load and associated kinematic error.

Dissociable effects of the implicit and explicit memory systems on learning control of reaching

“…Furthermore, our model predicts that if the force field is imposed gradually on the arm so that there are little or no visual cues to predict the direction of perturbation, there will be little probability to become aware, resulting in little or no generalization to the other arm. This is consistent with a recently reported result (Malfait and Ostry, 2004). Finally, one does not need to actually move their arm in a force field to become aware of the perturbation patterns.…”

“…This scenario is intriguing because it potentially can explain some puzzling recent results. Earlier work had found that training in a force field generalizes strongly to the trained arm in intrinsic coordinates but weakly to the opposite arm in extrinsic coordinates (Criscimagna-Hemminger et al, 2003;Malfait and Ostry, 2004). If performance is due to sum of a strong implicit internal model that depends on proprioception and a weak explicit internal model that depends on vision, then the patterns of generalization can be explained.…”

“…An internal model of dynamics that represents state of the arm in terms of proprioception predicts that when the arm experiences a pattern of force during reaching, there should be no transfer of learning to the contralateral arm. However, there is small but significant generalization from one arm to the other and the coordinate system appears to be Cartesian (Criscimagna-Hemminger et al, 2003;Malfait and Ostry, 2004). Moreover, a recent study showed that when an observer views a video of an actor reaching in a force field, he gains information that has a small but significant effect on his performance (Mattar and Gribble, 2005).…”

The extent of interlimb transfer following adaptation to a novel visuomotor condition does not depend on awareness of the condition

“…Seven subjects were tested in each of the three conditions. The number of subjects was determined based on a power analysis performed based on the data reported by Malfait and Ostry (2004).…”

“…If interlimb transfer occurred because of certain cognitive strategies, the direction of transfer should not vary regardless of task conditions (e.g., whether the left or the right arm learned the task first, whether initial direction or final position of reaching movement is assessed). However, it has been argued that interlimb transfer is primarily a result of a cognitive strategy that arises from the abrupt introduction of large kinematic or dynamic movement errors (Malfait and Ostry 2004). This argument is based on a finding that the large amount of interlimb transfer observed following adaptation to an abruptly introduced dynamic condition disappeared when the same dynamic condition was gradually introduced.…”