ABSTRACT
Prism adaptation involves two distinct processes: rapidly developing compensatory changes in motor control and more slowly developing realignment of spatial mapping functions. For example, on-line visual feedback control of the pointing limb reduces performance error induced by optical displacement of the visual field and off-line knowledge-of-results can be used to compensate for the displacement by setting a “virtual” target for initiation of feedforward control of the limb. Spatial realignment can be accomplished by altering the parameters of spatial transformations that map positions in limb space onto positions in visual space or map positions in visual space onto positions in limb space. Spatial realignment depends upon being able to compare the erroneous target position command that initiated movement with the effector position that achieved the target. Exposure performance alone is no indication of spatial realignment. In contrast, accurate exposure performance was slower to develop for the invisible-starting-position group in spite of substantial realignment of both visual and limb space.
