Scientific investigations of a descriptive nature involve in creasingly refined definitions of a problem. An idea is trans formed after initial experiments into a working hypothesis that has a number of testable consequences. Rarely in the neurosci ences do such tests completely falsify the hypothesis; more commonly they lead to a modified, more general hypothesis. One could argue that in order to define a scientific problem, one must first understand it. This monograph is an attempt to draw together knowledge and understanding from various disciplines, collected from studies carried out over more than 80 yr, of the functions of the auditory midbrain. This part of the brain has been of continuing interest to me, from my days as a postgraduate student in the mid-1960s to the present time, because so many ideas about central auditory organization and function have developed from studies of this region. This book is dedicated to Jerzy E. Rose, Professor Emer itus of Neurophysiology at the University of Wisconsin. His intellect and clarity of mind have been responsible for many of the modern ideas of auditory neurophysiology. These ideas have been incorporated into a series of classic papers on audi tory neuroscience that will be important for a long time to corne. In addition, Jerzy Rose has been an inspired teacher whose precepts of brain structure and function have been a major influence on his students, including the author."

Scientific investigations of a descriptive nature involve in creasingly refined definitions of a problem. An idea is trans formed after initial experiments into a working hypothesis that has a number of testable consequences. Rarely in the neurosci ences do such tests completely falsify the hypothesis; more commonly they lead to a modified, more general hypothesis. One could argue that in order to define a scientific problem, one must first understand it. This monograph is an attempt to draw together knowledge and understanding from various disciplines, collected from studies carried out over more than 80 yr, of the functions of the auditory midbrain. This part of the brain has been of continuing interest to me, from my days as a postgraduate student in the mid-1960s to the present time, because so many ideas about central auditory organization and function have developed from studies of this region. This book is dedicated to Jerzy E. Rose, Professor Emer itus of Neurophysiology at the University of Wisconsin. His intellect and clarity of mind have been responsible for many of the modern ideas of auditory neurophysiology. These ideas have been incorporated into a series of classic papers on audi tory neuroscience that will be important for a long time to corne. In addition, Jerzy Rose has been an inspired teacher whose precepts of brain structure and function have been a major influence on his students, including the author.

This monograph evolved from years of research into the auditory pathway and hearing of many species of marsupials. Its function is to give biologists, in par ticular neurobiologists, a broad description and review of what is known of the auditory sensory capacities and processing mechanisms in this large order of mammals. My initial interest in marsupials developed from collaborative work with Dr. Richard Gates at Monash and Melbourne Universities in the 1970s and by curiosity as to whether concepts about the auditory system was stimulated stemming from experiments mainly on domestic cats could be extended to mam mals of other orders. My subsequent interest in Australian marsupials, aroused by collaboration with Dr. John Nelson at Monash University in the 1980s and 1990s, concerned their auditory systems and behavior per se and not as primitive cousins of eutherians. More recently, I have collaborated with Dr. Bruce Masterton at Florida State University in studies of New World marsupials. His sad death in 1996 has robbed neurobiologists of one of our most provocative thinkers and hypothesis testers. I would like to thank the Department of Physiology at Monash University for making many facilities available to me, the National Health and Medical Research of Australia and the Australian Research Council for providing funds for Council research, and Jill Poynton and Michelle Mulholland, who illustrated this volume."

In contrast to the level of interest which is paid to the orga nization of meetings about the structure and function of the audi tory periphery, the central auditory system has received little attention in the last several years. However, much recent data accu mulated during this period has provided auditory physiologists with new ideas about the function of the central auditory system. The successful exploration of new anatomical tracing techniques (triti ated aminoacids, horseradish peroxidase, 2-deoxyglucose) together with the collection of electrophysiological data obtained with intra cellular and extracellular recordings from the receptors and neurones in the auditory pathway have considerably deepened our understanding of central auditory function. Particular interest was concentrated upon the development of the auditory system under normal conditions and in conditions ofaudi tory deprivation. Although, from the methodological point of view, the conditions of reversible auditory deprivation are complicated, promising new data appeared in this field. Similarly the specific ability of the auditory system to encode communication signals and speech sounds has been examined in many laboratories allover the world. A very fruitful method. based upon the results of electrical stimulation of cochlear nerve fibres in experimental animals, is the application of neuroprostheses in deaf patients. At the present time, the method still does not meet all requirements and many improvements will be necessary. Undoubtedly the exploration of the results of recent physiological experiments may help in the further improvement of neuroprostheses."