[1] Brown Univ, Dept Neurosci, Providence, RI 02912 USA
[2] Calif State Univ San Bernardino, Dept Biol, San Bernardino, CA 92407 USA
[3] Harvard Univ, Sch Med, Massachusetts Gen Hosp, Ctr Canc Res, Charlestown, MA 02129 USA
[4] Harvard Univ, Sch Med, Dept Pathol, Charlestown, MA 02129 USA
[5] Brown Univ, Dept Mol Biol Cell Biol & Biochem, Providence, RI 02912 USA
[6] Univ Bath, Dept Biol & Biochem, Bath BA2 7AY, Avon, England
[7] MIT, Dept Mech Engn, Cambridge, MA 02139 USA
[8] Univ Oregon, Inst Neurosci, Eugene, OR 97403 USA