## 4 Discussion
Changes in RE after 2 weeks differed according to the presence of complete sensory loss only in the severe motor paralysis group, suggesting that somatic sensory feedback contributes greatly to the improvement of reach motion in severely paralyzed patients. On the other hand, the RE scores of patients in the moderate and mild paralysis groups with complete sensory loss were within the range of patients without complete sensory loss. Thus, among patients with voluntary control of their shoulder and elbow on the paralyzed side, repeated robot training improves reach motion regardless of whether sensory disorder has occurred. Similar to the results for PE of patients with moderate and severe motor paralysis in this study, [PERSON] et al. (1995) reported that errors in the track during reach motion were great among patients with sensory disorder ([PERSON] et al. (1995). Thus, feedback of somatic sensation contributes greatly to the fine corrections of errors. [PERSON] et al. (2009) stated that visual information plays an important role in reach motion of patients with somatic sensory disorder and hypothesized that mild motor paralysis patients can compensate for errors caused by somatic sensory disorder through visual feedback ([PERSON] et al., 2009). They concluded that moderate and severe paralysis patients have difficulty in correcting errors based only on visual feedback. However, because a tendency is seen for PE to diminish, long-term robot training may result in further improvement. [PERSON] et al. (2009) stated that, in continuous motion, the excellence of proprioception was positively correlated with motor learning effects ([PERSON] et al., 2009). In our study, a similar relationship was observed in the severe motor paralysis group as a result of continuous robot training. These results suggest that, assuming sensory disorder has occurred, the effects of motor learning equal to that in patients without sensory loss can be obtained if the motor paralysis is not severe. The present study had encountered difficulties enrolling a sufficient number of patients with complete sensory loss. Therefore, we compared each evaluation score of the patients with complete sensory loss with the 95% reference range calculated using scores of the patients without complete sensory loss. Patients with moderate to severe motor paralysis have relatively large lesions ([PERSON] et al., 2009; [PERSON] et al., 2009), so that cognitive dysfunctions often appear. In several cases, to diagnose the sensory disorder which is assessed by listening to the patient's sense was difficult because of aphasia. The patients with cognitive dysfunctions also often had difficulty understanding the robot operation. For these reasons, it was difficult to recruit a sufficient number of patients with moderate to severe paralysis who had severe sensory impairment. On the other hand, for the patients with mild paralysis who marked high FMA scores at admission, some task-oriented and/or skill trainings rather than the robot training are performed in the clinical manner. Therefore, the number of patients with mild paralysis was small regardless of the presence or absence of sensory impairments. To further popularize robot training in clinics in the future, it will be necessary to ensure adequate numbers of samples, to verify effectiveness according to the length of the training period, and to optimize the effectiveness of robot training according to whether a patient has or has not suffered sensory loss.