" aDepartment of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
bDepartment of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
cState Key Laboratory for Brain and Cognitive Science, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China dCenter for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
eResearch Centre of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China Received 22 August 2006; accepted 22 August 2006