1. Department of Psychology and Helen Wills Neuroscience Institute (S.Z., E.Z., C.Y., L.J.K.), University of California, Berkeley, California 94720-1650
2. Department of Integrative Biology and Helen Wills Neuroscience Institute (G.E.B.), University of California, Berkeley, California 94720-1650
3. Laboratory of Integrative Brain Sciences (K.T.), Department of Biology, Waseda University, Tokyo 162-8480, Japan