1. Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA.
2. Center for Neuroengineering, Duke University, Durham, NC 27708, USA.
3. Laboratoire de Systèmes Robotiques, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
4. Department of Neurobiology, Duke University, Durham, NC 27708, USA.
5. Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA.
6. Edmond and Lily Safra International Institute of Neuroscience of Natal, Natal Rio Grande do Norte, 59055-060, Brazil.