1. Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
2. Department of Psychology, University of Toronto, Toronto, Ontario M5S 3G3, Canada.
3. Department of Physiology, University of Toronto, Toronto, Ontario M5G 1X8, Canada.
4. Institute of Medical Sciences, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
5. Brain, Mind & Consciousness Program, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario M5G 1M1, Canada.
6. RIKEN-MIT Laboratory for Neural Circuit Genetics at the Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
7. Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.