1. School of Engineering, Tokyo Institute of Technology, Yokohama 226-8503, Japan
2. Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226-8503, Japan
3. Department of Electrical Electronic and Computer Engineering (DIEEI), University of Catania, 95131 Catania, Italy
4. PRESTO, JST, 332-0012 Saitama, Japan
5. Integrative Brain Imaging Center, National Center of Neurology and Psychiatry, Tokyo 187-8551, Japan
6. ATR Brain Information Communication Research Laboratory Group, Kyoto 619-0288, Japan
7. Center for Mind/Brain Sciences (CIMeC), University of Trento, 38123 Trento, Italy