Inhibitory Function In Auditory Processing

There seems little doubt that from the earliest evolutionary beginnings, inhibition has been a fundamental feature of neuronal circuits - even the simplest life forms sense and interact with their environment, orienting or approaching positive stimuli while avoiding aversive stimuli. This requires internal signals that both drive and suppress behavior. Traditional descriptions of inhibition sometimes limit its role to the suppression of action potential generation. This view fails to capture the vast breadth of inhibitory function now known to exist in neural circuits. A modern perspective on inhibitory signaling comprises a multitude of mechanisms. For example, inhibition can act via a shunting mechanism to speed the membrane time constant and reduce synaptic integration time. It can act via G-protein coupled receptors to initiate second messenger cascades that influence synaptic strength. Inhibition contributes to rhythm generation and can even activate ion channels that mediate inward currents to drive action potential generation. Inhibition also appears to play a role in shaping the properties of neural circuitry over longer time scales. Experience-dependent synaptic plasticity in developing and mature neural circuits underlies behavioral memory and has been intensively studied over the past decade. At excitatory synapses, adjustments of synaptic efficacy are regulated predominantly by changes in the number and function of postsynaptic glutamate receptors. There is, however, increasing evidence for inhibitory modulation of target neuron excitability playing key roles in experience-dependent plasticity. One reason for our limited knowledge about plasticity at inhibitory synapses is that in most circuits, neurons receive convergent inputs from disparate sources. This problem can be overcome by investigating inhibitory circuits in a system with well-defined inhibitory nuclei and projections, each with a known computational function. Compared to other sensory systems, the auditory system has evolved a large number of subthalamic nuclei each devoted to processing distinct features of sound stimuli. This information once extracted is then re-assembled to form the percept the acoustic world around us. The well-understood function of many of these auditory nuclei has enhanced our understanding of inhibition's role in shaping their responses from easily distinguished inhibitory inputs. In particular, neurons devoted to processing the location of sound sources receive a complement of discrete inputs for which in vivo activity and function are well understood. Investigation of these areas has led to significant advances in understanding the development, physiology, and mechanistic underpinnings of inhibition that apply broadly to neuroscience. In this series of papers, we provide an authoritative resource for those interested in exploring the variety of inhibitory circuits and their function in auditory processing. We present original research and focused reviews touching on development, plasticity, anatomy, and evolution of inhibitory circuitry. We hope our readers will find these papers valuable and inspirational to their own research endeavors.

The symposium that has provided the basis for this book, "Plasticity of the Central Auditory System and Processing of Complex Acoustic Signals" was held in Prague on July 7-10, 2003. This is the fourth in a series of seminal meetings summarizing the state of development of auditory system neuroscience that has been organized in that great world city. Books that have resulted from these meetings represent important benchmarks for auditory neuroscience over the past 25 years. A 1980 meeting, "Neuronal Mechanisms of Hearing" hosted the most distinguished hearing researchers focusing on underlying brain processes from this era. It resulted in a highly influential and widely subscribed and cited proceedings co-edited by professor Lindsay Aitkin. The subject of the 1987 meeting was the "Auditory Pathway - Structure and Function". It again resulted in another important update of hearing science research in a widely referenced book - edited by the late Bruce Masterton. While the original plan was to hold a meeting summarizing the state of auditory system neuroscience every 7 years, historical events connected with the disintegration of the Soviet Empire and return of freedom to Czechoslovakia resulted in an unavoidable delay of what was planned to be a 1994 meeting. It wasn't until 1996 that we were able to meet for the third time in Prague, at that time to review "Acoustical Signal Processing in the Central Auditory System".

Chermak and Musiek's two-volume, award-winning handbooks are back in newly revised editions. Extensively revised and expanded, Volume I provides comprehensive coverage of the auditory neuroscience and clinical science needed to accurately diagnose the range of developmental and acquired central auditory processing disorders in children, adults, and older adults. Building on the excellence achieved with the best-selling 1st editions which earned the 2007 Speech, Language, and Hearing Book of the Year Award, the second editions include contributions from world-renowned authors detailing major advances in auditory neuroscience and cognitive science; diagnosis; best practice intervention strategies in clinical and school settings; as well as emerging and future directions in diagnosis and intervention. Exciting new chapters for Volume II include: Development of the Central Auditory Nervous System, by Jos J. EggermontCausation: Neuroanatomic Abnormalities, Neurological Disorders, and Neuromaturational Delays, by Gail D. Chermak and Frank E. MusiekCentral Auditory Processing As Seen From Dichotic Listening Studies, by Kenneth Hugdahl and Turid HellandAuditory Processing (Disorder): An Intersection of Cognitive, Sensory, and Reward Circuits, by Karen Banai and Nina KrausClinical and Research Issues in CAPD, by Jeffrey Weihing, Teri James Bellis, Gail D. Chermak, and Frank E. MusiekPrimer on Clinical Decision Analysis, by Jeffrey Weihing and Sam AtchersonCase Studies, by Annette E. HurleyThe CANS and CAPD: What We Know and What We Need to Learn, by Dennis P. Phillips

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.

Auditory information processing refers to the capability of interpreting sounds heard by an individual. Central auditory processing plays an important role in recognizing incoming sounds, analyzing them and assigning meaning to them. It comprises steps related to information processing, which includes mechanical, electrical, chemical and central processing. The auditory system comprises the sensory organs, such as ears, as well as the auditory components of the sensory system. Excitatory neurons have a dominant function in the auditory cortex that transfers sensory information within and across brain areas. Inhibitory interneurons on the other hand, perform a variety of modulatory activities that determine how information is represented and processed. Inhibition has long been a characteristic of neuronal circuits. It helps to generate rhythms and is even capable of activating ion channels, which mediates an inward current that leads to the generation of action potentials. This book contains some path-breaking studies on auditory information processing. It will serve as a valuable source of reference for graduate and post graduate students. The readers would gain knowledge that would broaden their perspective about this area of study.

The study of bilingualism has charted a dramatically new, important, and exciting course in the 21st century, benefiting from the integration in cognitive science of theoretical linguistics, psycholinguistics, and cognitive psychology (especially work on the higher-level cognitive processes often called executive function or executive control). Current research, as exemplified in this book, advances the study of the effects of bilingualism on executive function by identifying many different ways of being bilingual, exploring the multiple facets of executive function, and developing and analyzing tasks that measure executive function. The papers in this volume (21 chapters), by leading researchers in bilingualism and cognition, investigate the mechanisms underlying the effects (or lack thereof) of bilingualism on cognition in children, adults, and the elderly. They take us beyond the standard, classical, black-and-white approach to the interplay between bilingualism and cognition by presenting new methods, new findings, and new interpretations.