Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul 120-752, Korea, Department of Bio and Brain Engineering, KAIST, Yuseong-Gu, Daejeon 305-701, Korea.|Stanley Brain Research Laboratory, Stanley Medical Research Institute, Rockville, MD 20850, USA and.|School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.|Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul 120-752, Korea.|Department of Bio and Brain Engineering, KAIST, Yuseong-Gu, Daejeon 305-701, Korea.