1. Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Viale del Risorgimento 2, 40136 Bologna, Italy
2. Neuroelectronics, Munich Institute of Biomedical Engineering, Department of Electrical Engineering, Technical University of Munich, 85748 Garching, Germany
3. Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
4. Institute of Biological Information Processing (IBI-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany