1. Redwood Center for Theoretical Neuroscience, University of California at Berkeley, Berkeley, CA, USA
2. Neuromorphic Computing Laboratory, Intel Labs, Santa Clara, CA, USA
3. Department of Computer Science Electrical and Space Engineering, Luleå University of Technology, Luleå, Sweden
4. Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, CA, USA
5. IBM Research–Zurich, Rüschlikon, Switzerland