1. Department of Computer Science and Engineering, School of Engineering and Applied Science, Washington University in St. Louis, St. Louis, MO 63130, USA.
2. Sensory Neurobiology Group, Queensland Brain Institute, University of Queensland, St. Lucia, Queensland 4072, Australia.
3. Department of Electrical Engineering and Computer Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
4. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
5. Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.