1. Brain Research Institute, University of Zurich, Zurich, Switzerland
2. Neuroscience Center Zurich, University of Zurich, Switzerland
3. Experimental Neurology Center, Department of Neurology, Inselspital University Hospital Bern, Bern, Switzerland
4. Present address: Institute of Cellular and Integrative Neurosciences, University of Strasbourg and CNRS, Strasbourg, France