1. Y. H. Cho and H. Eichenbaum, Department of Psychology, Boston University, Boston, MA 02215, USA.
2. K. P. Giese and A. J. Silva, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
3. H. Tanila, Department of Neuroscience and Neurology, University of Kuopio, 70211 Kuopio, Finland.