The mechanisms of sensorimotor adaptation will be studied, focusing on the rapid recalibration of visually guided reaching after exposure to altered visual feedback. This research will use a combination of human psychophysical experiments and computational modeling to gain a detailed understanding of how sensory feedback drives recalibration of the visuomotor map. A virtual reality based psychophysical apparatus will be used to introduce spatial perturbations to the visual feedback of the arm in a manner analogous to the classic """"""""prism adaptation"""""""" experiments. A range of psychophysical measurements will be used to quantify the adaptive response at intermediate stages along the transformation from vision to movement including eye-body and body-arm calibration as well as a learned corrective response. This research will focus on three specific aims: (1) A study of the temporal dynamics of visuomotor adaptation. The trial-by-trial statistics of both the motor output and the sensory feedback will be collected and will be used to test several classes of computational models for the """"""""learning rules"""""""" that specify how sensory feedback from each single tidal effects the visuomotor map and, consequently, the next movement. (2) A study of spatial generalization in reach adaptation. The effect that feedback from reaches to one target location has on subsequent movements to other target locations will be determined. These patterns of spatial generalization will be used to model the adaptive degrees of freedom of the visuomotor map and to test compositional models of the sequence of transformations from vision and movement. (3) A study of the """"""""credit assignment"""""""" problem in reach adaptation: given that error corrective sensory feedback can drive adaptation at multiple stages of the visuomotor pathway, how does the brain determine which loci of adaptation should respond to the feedback from a given movement? Manipulations of the timing of the sensory feedback, the feedback signals that are available, and the extent and shape of the visual perturbations will all be performed, and the distribution of adaptive responses across the visuomotor pathway will be measured. These data will be used to model the rules by which credit assignment is accomplished. The long-term goals of this work are to gain a more quantitative understanding of sensorimotor integration in limb movements and to identify the behavioral and neural bases of reach adaptation, as a model for sensorimotor plasticity in the central nervous system. ? ?
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