The Long-Term Absence of Static Stereopsis Cultivates Adaptive Planning of Reaching-to-Grasp.

Purpose: To determine how the absence of stereopsis affects sensorimotor adaptation in visually guided reaching-to-grasp by comparing slant perception and depth-directed motor control between adults with long-term stereoblindness and typically sighted adults. Methods: Twenty-four adults (12 stereoblind, 12 typically sighted) completed a slant-matching task (perceptual estimate of surface orientation) and a reaching-to-grasp task (motor execution in depth). Outcomes indexed perceptual accuracy and grasp kinematics, including approach speed and the timing of grip alignment to surface slant. Results: Groups performed comparably on slant matching, but the stereoblind group adopted distinct grasping strategies, characterized by a faster approach to the target and delayed grip alignment relative to controls. Conclusions: Findings indicate adaptive reorganization of motor planning following long-term deprivation of static binocular (disparity) cues. The visuomotor system appears to recalibrate the balance between feedforward and feedback control-placing greater weight on real-time sensory information when anticipatory planning is constrained-highlighting flexible, ecological pathways for development and adaptation.