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Jonathan J. Marotta, Gerald P. Keith, John D. Crawford; Is reversing prism adaptation global or modular?. Journal of Vision 2004;4(8):290. doi: 10.1167/4.8.290.
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© ARVO (1962-2015); The Authors (2016-present)
We trained subjects on a left-right reversing prism with different amounts of stimulus location and orientation feedback to determine if a central spatial representation of the world is used by the higher-order control system that governs reaching and grasping. If a global system exists, then left-right reversal information in either feature would drive adaptation in both responses. A more modular system would drive learning in individual systems separately. In the baseline task, subjects were required to reach out and “grasp” a rectangle presented on an LCD. 4 training sessions: Laser Location (target disks, feedback glimpse of a laser dot indicating final hand position and the target); Hand View Location (target disks, glimpse of hand and target); Orientation (randomly oriented rectangle, glimpse of hand and target); Full Cue (rectangles at varying orientations and locations, glimpse of hand and target). Even though Left-Right reversal information was present in both the Orientation and Laser Location sessions, there was no transfer of learnt information from the reach (location) system to the grasp (orientation) system or visa versa. In contrast, following the Hand View Location session, subjects not only corrected their location (p<0.001) but also showed a significant correction in their orientation (p<0.05). It appears that even a slight glimpse of the hand provides enough orientation feedback to allow for a correction by the grasp (orientation) system. After the Full Cue session, subjects showed a correction for the prism reversal effect in the orientation (p<0.001) and position (p<0.001) of their reach and grasp. These results suggest that there is no common spatial representation of the world that is used by the higher-order control system to govern reaching and grasping. Rather, active exploration within each visuomotor system, particularly for the location-reach system, is required to weigh the cost-benefit function toward adaptation in these individual systems.
CIHR INMHA to JJM, CIHR & Canada Research Chair program to JDC, & OGS to GPK
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