[1] Howard Hughes Med Inst, Ashburn, VA 20147 USA
[2] Univ Calif San Diego, Howard Hughes Med Inst, Dept Neurosci, La Jolla, CA 92093 USA
[3] Univ Calif San Diego, Howard Hughes Med Inst, Dept Neurobiol, La Jolla, CA 92093 USA
[4] Columbia Univ, Columbia Coll Phys & Surg, Howard Hughes Med Inst, Dept Biochem & Mol Biophys, New York, NY 10032 USA
[5] Columbia Univ, Columbia Coll Phys & Surg, Howard Hughes Med Inst, Dept Neurosci, New York, NY 10032 USA