1. Department of Bioengineering, Stanford University, Stanford, CA, USA.
2. Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA.
3. Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA.
4. Institute for Biology, Humboldt Universität zu Berlin, D-10115 Berlin, Germany.
5. Experimental Biophysics, Humboldt Universität zu Berlin, D-10115 Berlin, Germany.