Coordination deficits in ideomotor apraxia during visually targeted reaching reflect impaired visuomotor transformations

▶ Hypothesis: Deficits in apraxia during targeted reaching arise from impaired sensorimotor transformations. ▶ Healthy controls, non-apraxic and apraxic left hemisphere damaged patients reached to three targets. ▶ Apraxic patients failed to consistently initiate their motion in the direction of the target. ▶ They showed large initial direction errors, larger variability and greater trajectory curvature. ▶ Deficits were the largest for the target requiring maximum shoulder and elbow coordination. ▶ These deficits reflect impaired planning associated with an inability to transform external visual information into motor commands that predict accurate dynamics.