1. T. V. P. Bliss is in the Division of Neurophysiology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
2. G. L. Collingridge is at the MRC Centre for Synaptic Plasticity, University of Bristol, Bristol BS8 1TD, UK.
3. S. Laroche is at Neurobiologie de l'Apprentissage, de la Mémoire et de la Communication (NAMC), CNRS UMR 8620, Universite Paris Sud, 91405 Orsay, France.