1. Department of Neurosurgery, Institute of Medicine, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
2. International Medical Center, University of Tsukuba Hospital, Tsukuba 305-8576, Ibaraki, Japan
3. Department of Rehabilitation Medicine, Institute of Medicine, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
4. Department of Occupational Therapy, Ibaraki Prefectural University of Health Sciences, Ami 300-0394, Ibaraki, Japan
5. Institute of Systems and Information Engineering, University of Tsukuba, Tsukuba 305-8573, Ibaraki, Japan
6. Ibaraki Prefectural University of Health Sciences, Ami 300-0394, Ibaraki, Japan