1. Department of Life Sciences, University of Trieste, Via Giorgieri 1, Trieste I-34127, Italy, Department of Electrotechnics, Electronics and Informatics, University of Trieste, Via A. Valerio 10, Trieste I-34127, Italy, and Sector of Neurobiology, International School for Advanced Studies (SISSA), 34014 Trieste, Italy