1. Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, South Korea
2. Centre for Synaptic Plasticity, School of Physiology and Pharmacology, Dorothy Hodgkin Building, Whitson St., Bristol BS1 3NY, UK
3. Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
4. Department of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151-746, South Korea