1. Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong
2. Laboratory for Functional Optical Imaging, Department of Biomedical Engineering, Columbia University, New York, New York 10027, USA
3. Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, New York 10027, USA
4. Advanced Biomedical Instrumentation Centre, Hong Kong Science Park, Shatin, New Territories, Hong Kong