[1] CNR, Ist Sistemi Complessi, I-50125 Florence, Italy
[2] Univ Catania, Dipartimento Fis & Astron, I-95123 Catania, Italy
[3] Univ Catania, Ist Nazl Fis Nucl, I-95123 Catania, Italy
[4] Univ Zaragoza, Inst Biocomputac & Fis Sistemas Complejos, E-50009 Zaragoza, Spain
[5] Univ Zaragoza, Dept Fis Teor, E-50009 Zaragoza, Spain
[6] Hop La Pitie Salpetriere, CNRS, UPR 640, Lab Neurosci Cognit & Imagerie Cerebrale,LENA, F-75651 Paris 13, France