1. Brain Research Center, National Chiao Tung University, Hsinchu, Taiwan
2. Department of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu, Taiwan
3. Department of Biological Science and Technology, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan
4. Graduate Institute of Automation and Control, National Taiwan University of Science and Technology, Taipei, Taiwan
5. Department of Mechanical Engineering, Hsiuping University of Science and Technology, Taichung, Taiwan