Acknowledgments

This work was supported by a French GIS contract on Cognitive Sciences entitled ``Dynamical coding of information by asymmetric recurrent neural networks''. The collaboration includes the following labs: ETIS - Cergy-Pontoise (M. Quoy - P. Gaussier), ONERA-CERT - Toulouse (E. Daucé - M. Samuelides), INSERM U455 - Toulouse (B. Doyon) and INLN - Nice (B. Cessac). We would like to thank all these colleagues for helpful comments and discussions.