1 Department of Computer Science, University of Cyprus, P.O. Box 20537, Nicosia, 1678, Cyprus. Electronic address: cchrist@cs.ucy.ac.cy.
2 Department of Computational Neuroscience, Institute of Physiology, Czech Academy of Sciences, Videnska 1083, Prague 4, 14220, Czech Republic. Electronic address: kostal@biomed.cas.cz.
3 Department of Mathematics "G. Peano", University of Torino, Via Carlo Alberto 10, 10123, Turin, Italy. Electronic address: laura.sacerdote@unito.it.