(p. v) Series Preface
(p. v) Series Preface
Auditory science has been, over the past three decades, one of the fastest growing areas of biomedical research. Worldwide there are now perhaps 10 000 researchers whose primary job is auditory research, and ten times that number working in allied, mainly clinical, hearing professions. This rapid growth is attributable to and, in turn, fuelled by several major developments in our understanding. While this Handbook focuses on fundamental research and underlying mechanisms, it does so from the perspective of understanding the impact of auditory science on the quality of our life. That impact has been realized through the explosive growth of digital technology and microelectronics, and delivered by devices as diverse as MP3 compression for music listening (based on models of perceptual coding) to the latest instruments for the management of hearing loss, including digital hearing aids and multichannel cochlear implants. The discovery of otoacoustic emissions (OAEs) – sounds produced by the cochlea – has enabled a step change both in our understanding of ear function and in the development of a clinical tool for deafness screening in newborn infants.
Fundamental research on the inner ear has shown that an elaborate system of sound-induced active processes, acting through the outer hair cells, serves to improve sensitivity, sharpen frequency tuning, dynamically modulate the mechanical response of the ear to sound, and create sound energy that passes back out of the ear. Each of these processes is also influenced by descending neural input to the hair cells. Most recently, the molecular machinery underlying these incredible phenomena has been explored and described in detail. The development, maintenance, and repair of the ear are also subjects of contemporary interest at the molecular level, as is the genetics of hearing disorders due to cochlear malfunctions. The auditory brain is responsible for sound (including speech) identification and localization. Through functional neuroimaging in humans, and the application of novel methods in animals, such as multichannel recordings of single unit activity, multiple cortical and subcortical areas necessarily involved in hearing and listening have now been identified and characterized. These areas occupy the superior (dorsal) temporal cortex, and extend into non-classical cortical regions, including the more rostral and ventral temporal lobe, the limbic system, and elsewhere in the frontal and parietal lobes. Understanding of subcortical processing has expanded through the use of molecular and cellular techniques in vitro and recordings in awake and behaving humans and animals in vivo. Increasingly, the widespread descending pathways are being shown to have profound functional importance, and to influence the coding of both simple and complex sounds. Recent studies of hearing (auditory perception) have shown how our perceptions relate to the underlying physiological mechanisms. For example, behavioural measures of peripheral auditory function have led to the development of sophisticated models of cochlear processing in humans. These models are having widespread influence in understanding both normal and pathological hearing. At the same time, there has been an increasing focus on auditory ‘ecology’, on complex sound perception in real (or virtual) environments. Traditional distinctions between spectral, temporal, and binaural processing have evolved into more functional concerns, including auditory scene analysis and auditory object perception.
Here, then, are the three major domains of auditory science – the ear, the brain, and hearing – and I am proud to present a corresponding three-volume Handbook. However, as the volume (p. vi) editors and I started sifting through all the areas we wished to cover, a number of recent developments in our science became apparent that made us question the way in which we had decided to partition the field. Spurred on by ever-increasing knowledge, the availability of enabling technology, and cultural shifts in attitudes towards ‘relevance’ and ‘interdisciplinary’ research, the three domains have begun to blur into one. Several instances of this are hinted at above: a transition from more segmented to more holistic approaches to audition; a shift in focus from more simple to more complex and, hence, more realistic sounds; and a drilling down across traditional disciplinary boundaries from the phenomenological to the mechanistic and generic. Dynamic properties of hearing are becoming more prominent across all three domains, and beyond, as lifespan development, adaptation, and learning receive increasing recognition. Reciprocal influences of hearing on and from cognition (attention, memory, and emotion), action, and vision add to a picture of a powerful, working, integrated sense that is arguably the most important we possess for what makes us distinctly human – our social interaction with our world. Organizationally, researchers at all levels (peripheral, central, and perceptual) now work increasingly together, with many major and several new interdisciplinary centres of auditory science dotted across the globe.
Our ambitious aim has been to deliver a working Handbook that would fill an unmet need for a single reference work spanning all of auditory science. We wanted it to offer a basic background for all those interested in the subject, from the curious undergraduate to the professional researcher and clinician, while also capturing the excitement, and some of the detail, of the most recent developments in this rapidly evolving discipline. Consequently, we set out with the conflicting aims of producing a comprehensive, even definitive work, but of completing it within the minimum time possible. We optimistically targeted this at one year, recognizing that the finished product would have a finite lifespan. In fact, the preparation of the chapters, from commissioning to collection of the final versions of the final chapters, has taken about two years. Although disappointing to us, Martin Baum, our very helpful and ever patient senior commissioning editor at Oxford University Press, has tried to console us, suggesting that even this effort has been something of a world record.
I knew at the outset of this project that its success would be completely dependent on the recruitment of the right volume editors. I feel incredibly lucky and humbled to have retained the services of four colleagues whose insight, experience, determination, interpersonal skills, and sheer hard work have managed to get this Handbook together more quickly than some of my own previous book chapters have taken to be read by the book’s editors, and more professionally than I had dreamed possible. Many, many thanks to all four – my dedication is to you.
David R Moore
MRC Institute of Hearing Research