[1] Univ Calif San Diego, Div Biol Sci, Neurobiol Sect, La Jolla, CA 92093 USA
[2] Univ Calif San Diego, Inst Nonlinear Sci, Dept Phys, Marine Phys Lab,Scripps Inst Oceanog, La Jolla, CA 92093 USA
[3] Max Planck Inst Med Res, Dept Biomed Opt, D-69120 Heidelberg, Germany