PAX5 deficiency of the patient causes impaired motor control and learning. (A–D) Visuomotor adaptation task (Video 1). (A) Schematic illustration of the hand movement angles and error angle magnitudes during a single adaptation step. As the movement angle approaches the inverse of the perturbation angle, the error magnitude decreases. In other words, participants compensate with their movements for the perturbation by minimizing the magnitude of the end-point error. (B) Visuomotor adaptation task. Hand movement traces of the patient (red) and a representative control (blue) during adaptation to the perturbation (black line). Right: Estimated execution noise (ε) parameters. 95% credible interval (CI) of the patient (red; σε = 4.81, 95% CI 4.35–5.36) shown against the distribution of the controls (mean in blue; σε = 2.02, 95% CI 1.90–2.14; n = 60). (C) Parameter estimates of the retention rate, learning rate, and planning noise, respectively. The patient’s mean value and 95% CI are shown in red (retention rate = 0.98, 95% CI 0.97–0.99; learning rate = 0.11, 95% CI 0.07–0.18; planning noise = 0.43, 95% CI 0.24–0.99). The mean value of the control group (n = 60) is shown in blue. The blue bars represent the density distribution for all controls. (D) Mean reaction and movement times of controls (blue; n = 60) and patient (red) across all trials. The reaction time was defined as the time from the appearance of the target until movement initiation. The movement time was defined as the time from movement initiation until movement end. (E) Data summary of the visuomotor assessment tasks (Video 2). Performance matrix of the indicated tasks is shown for the patient and controls (n ≥ 7) with percentage of correct trials, using the mean value of the controls. (F) Visuomotor assessment tasks. Time reflecting eye and hand latency of the patient and controls (n ≥ 9) during the pro-saccade, pro-tapping, and trajectory prediction trials, respectively (Video 2). Two-tailed one-sample t test (D and F); **, P < 0.01; ****, P < 0.0001. For detailed statistical information (D and F), see Table S6. Each dot represents one individual (D and F).