Components of prism adaptation in terminal and concurrent exposure: Organization of the eye-hand coordination loop

Abstract

In three experiments, aftereffect measures of visual-shift and proprioceptive-shift components and total shift in eye-hand coordination were obtained for prism exposure. In one condition the hand was visible for most of the sagittal pointing movement (concurrent exposure), whereas in the other condition only the fingertip was visible at the end of the movement (terminal exposure). Visual shift was greater than proprioceptive shift with terminal exposure and the reverse was true with concurrent exposure, except that proprioceptive shift tended to be greater in both exposure conditions when head movement was permitted. Total shift was not different from the sum of its components except when targets were present, in which case total shift tended to be greater than the sum. Proprioceptive aftereffects for the unexposed hand were small except when head movement was permitted and appeared to be related to changes in felt head position. Aftereffects for target pointing with the unexposed hand were not found to be related to visual shift. The results are discussed in terms of a view of the eye-hand coordination loop as a serial linkage of component eye-head and hand-head systems, with the locus of adaptation determined by the direction of the coordinative linkage between component systems. © 1988 Psychonomic Society, Inc.