ACTIVITY-DEPENDENT CHANGES IN A NEURONAL CIRCUIT IMPORTANT FOR SOUND LOCALIZATION Dissertation of the Graduate School of Systemic Neurosciences of Ludwig-Maximilians-University Munich Submitted by Benjamin Haßfurth Munich, May 2010 Supervisor: PD Dr. Ursula Koch Second expert appraiser: Prof. Benedikt Grothe Day of the oral defense: 31.08.2010 2 Für meine Familie 3 4 TABLE OF CONTENTS SUMMARY 9 ZUSAMMENFASSUNG 13 1 INTRODUCTION 1.1 The evolution of hearing 17 1.2 Sound transmission in the ear 19 1.3 Auditory processing 21 1.4 The superior olivary complex - interaural level differences and interaural time differences 25 1.5 Early developmental changes in the superior olivary complex - preparing for the acoustic environment 30 1.6 Activity-dependent adaptations in the superior olivary complex - optimizing sound localization 32 1.7 GABA receptors and their relevance for auditory processes 34 B1.8 HCN channels - structure and function 37 1.9 Aims of this study 39 2 MATERIAL AND METHODS 2.1 General methods 41 2.2 HCN channel specific methods 42 2.2.1 Drugs and solutions 42 2.2.2 Data acquisition and analysis 42 2.2.3 Cochlear ablations 43 2.