1. Department of Biology (T.U., K.I., Y.F., T.M., K.T.), Waseda University, and Center for Medical Life Science of Waseda University, 162-8480, Japan
2. Section of Behavioral Sciences (K.U.), Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima, 739-8521, Japan
3. Department of Psychology and Helen Wills Neuroscience Institute (L.J.K), University of California, Berkeley, California 94720