Chaya Kalcheim1, Hermann Rohrer2. 1. Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and The Safra Center for Brain Research (ELSC), Hebrew University of Jerusalem, Hadassah Medical School, Jerusalem, Israel. kalcheim@cc.huji.ac.il hermann.rohrer@brain.mpg.de. 2. Research Group Developmental Neurobiology, Max Planck Institute for Brain Research, Frankfurt/M, Germany. kalcheim@cc.huji.ac.il hermann.rohrer@brain.mpg.de.