This text explores the shared and contrasting strategies for signalling and processing sensory information within auditory and tactile sytems and describes their physiologic organization. It brings together researchers in aspects of sensory physiology whose studies are linked by their reliance upon mechanoreceptor mechanisms. The book has a strong functional emphasis and is based on electrophysiological analyses from the receptor level to the anatomic level, probing the sensory and motor areas of the cerebral cortex. It presents recent research data on mechanisms of auditory transduction, efferent control of cochlear function, the coding of information about sound intensity, directional aspects of hearing, frequency parameters of simple and complex vibrotactile stimuli, development and reorganization within auditory tactile systems, the application of fundamental sensory research to the problems of deafness.

This book explains neural function at the level of ion channels and membrane excitability in neurons along the ascending auditory pathway. Airborne sound information is captured by the ears, transformed to neural electrical signals, and then processed in the brain. Readers will find full descriptions of these processes of signal transduction and transformation. First, it is described how, at the level of hair cells, the receptor cells in the cochlea, the sound-evoked vibration is transduced to electrical signals and transmitted to the auditory nerve fibers. In the second section it is explained how the electrical activity of these fibers is processed at the cochlear nucleus in order to extract the temporal and level information of sound separately and then transmitted to the third nucleus for processing of the interaural differences, such as the interaural time difference and the interaural level difference. The third section summarizes the transformation of auditory temporal information to the rate of neural firing activity in the midbrain and the higher nuclei, including the cortex, based on in vivo results. Finally, emerging new technologies to investigate auditory signal processing are reviewed and discussed.

The auditory system is a complex neural system composed of many types of neurons connected into networks. One feature that sets the auditory system apart from other sensory systems, such as somatosensory or visual systems, is the many stages of neural processing that occur between the ear in the periphery and the cerebral cortex. Each stage is composed of specialized types of neurons connected in specific microcircuits that perform computations on the information about sound. To understand this processing, all the tools of neuroscience must be employed. The proposed text integrates cell biology, synaptic physiology, and electrophysiology to fully develop the topic, presenting an overview of the functional anatomy of the central auditory system. It is organized based on the neuronal connectivity of the central auditory system, which emphasizes the neurons, their synaptic organization, and their formation of functional pathways and microcircuits. The goal of the book is to stimulate research into the cell biology of the central auditory system and the characteristics of the specific neurons and connections that are necessary for normal hearing. Future research on the development of the central auditory including that employing stem cells will require such information in order to engineer appropriate therapeutic approaches. ​

A number of first and second order neurons of the guinea pig auditory system were studied extensively in an attempt to determine the method by which information is conveyed. Single neuron electrophysiological techniques with anatomical controls were used in the study and in response to several different stimuli, various response patterns were observed. Statistical methods of analysis, using a digital computer, were employed. Each fiber in the auditory nerve appears to convey only fragmentary information; therefore, the information carried by a number of fibers is required to extract all the information about a single signal. The data suggest that a pulse density modulation system of encoding is used, in which the 'carrier' appears to be the irregular spontaneous background activity, the pulse density of which is actively increased and decreased to convey information about both pitch and loudness. The system appears to be much more sensitive to sound changes than to absolute values. For example, pulse density correlated far better with rate-of-change of stimulus intensity than with absolute levels of intensity. In addition to frequency and amplitude, the interval between successive stimuli may be an important parameter of stimulation.

There has been substantial progress in understanding the contributions of the auditory forebrain to hearing, sound localization, communication, emotive behavior, and cognition. The Auditory Cortex covers the latest knowledge about the auditory forebrain, including the auditory cortex as well as the medial geniculate body in the thalamus. This book will cover all important aspects of the auditory forebrain organization and function, integrating the auditory thalamus and cortex into a smooth, coherent whole. Volume One covers basic auditory neuroscience. It complements The Auditory Cortex, Volume 2: Integrative Neuroscience, which takes a more applied/clinical perspective.