1. Microsoft Research , Microsoft , 300 Lafayette St, New York, NY 10012, USA
2. Department of Psychiatry and Behavioral Sciences, Johns Hopkins University , 600 N Wolfe St, Baltimore, MD 21205, USA
3. Neurotechnology R & D Unit, Araya Inc , 6F Sanpo Sakuma Building, 1-11 Kandasakumacho, Chiyoda-ku, Tokyo 101-0025, Japan