1 Laboratory for Glia-Neuron Circuit Dynamics, RIKEN Center for Brain Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. Electronic address: jun.nagai@riken.jp.
2 Department of Neurophysiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan; PREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan. Electronic address: Tetsuya.takano@keio.jp.