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.