About the Authors
Graduate School of Information Science and Technology, the University of Tokyo, Bunkyo, Tokyo, Japan
Amari Research Unit, RIKEN Brain Science Institute, Wako, Saitama, Japan
Center for Neural Science, New York University, New York, New York, United States of America
The authors have declared that no competing interests exist.
NM and BD conceived and designed the experiments. NM and BD performed the experiments. NM and BD wrote the paper.