The Effects of Separating Visual and Motor Workspaces on the Generalization of Visuomotor Adaptation across Movement Conditions
Date of Award
Master of Science (MS)
Johnson, Michelle J.
Schmit, Brian D.
Separating visual and proprioceptive information in terms of workspace locations during reaching movement has been shown to disturb transfer of visuomotor adaptation across the arms. Here, we investigated whether separating visual and motor workspaces would also disturb generalization of visuomotor adaptation across movement conditions within the same arm. In our behavioral study, subjects were divided into four experimental groups (plus three control groups). The first two groups adapted to a visual rotation under a "dissociation" condition in which the targets for reaching movement were presented in midline while their arm performed reaching movement laterally. Following that, they were tested in an "association" condition in which the visual and motor workspaces were combined in midline or laterally. The other two groups first adapted to the rotation in one association condition (medial or lateral), then were tested in the other association condition. The latter groups demonstrated complete transfer from the training to the generalization session, whereas the former groups demonstrated substantially limited transfer. In our fMRI study, we examined brain activity while subjects learned a visuomotor adaptation task in a condition in which visual and motor workspaces were either dissociated or associated with each other, and subsequently performed the same visuomotor task with the same hand in a condition in which visual and motor workspace were associated. Our main results showed that the neural involvement is similar between the early training and the early generalization phases in the `dissociation-to-association' conditions; while that is similar between the late adaptation and the early generalization phases in the `association-to-association' condition. These findings suggest that a visual-proprioceptive conflict in terms of workspace locations disrupts the development of a neural representation, or an internal model, that is associated with novel visuomotor adaptation, thus resulting in limited generalization of visuomotor adaptation.