Computational structure of coordinate transformations: A generalization study

Zoubin Ghahramani, Daniel M. Wolpert and Michael I. Jordan
Department of Brain & Cognitive Sciences,
Massachusetts Institute of Technology, Cambridge, MA 02139

One of the fundamental properties that both neural networks and the central nervous system share is the ability to learn and generalize from examples. While this property has been studied extensively in the neural network literature it has not been thoroughly explored in human perceptual and motor learning. We have chosen a coordinate transformation system---the visuomotor map which transforms visual coordinates into motor coordinates---to study the generalization effects of learning new input--output pairs. Using a paradigm of computer controlled altered visual feedback, we have studied the generalization of the visuomotor map subsequent to both local and context-dependent remappings. A local remapping of one or two input-output pairs induced a significant global, yet decaying, change in the visuomotor map, suggesting a representation for the map composed of units with large functional receptive fields. Our study of context-dependent remappings indicated that a single point in visual space can be mapped to two different finger locations depending on a context variable---the starting point of the movement. Furthermore, as the context is varied there is a gradual shift between the two remappings, consistent with two visuomotor modules being learned and gated smoothly with the context.

In G. Tesauro, D.S. Touretzky, and J. Alspector (eds.), Advances in Neural Information Processing Systems 7. Morgan Kaufmann Publishers, San Francisco, CA, 1995. postscript.

Back to Zoubin Ghahramani's Home Page,