The Auditory System in Sleep

By Ricardo Velluti

The Auditory System in Sleep, Second Edition presents a view of a sensory system working in a different state, that of the sleeping brain. This updated edition contains new chapters on topics such as implanted deaf patients and sleep and tinnitus treatments. It is written for basic auditory system and sleep researchers, as well as practitioners and clinicians in the Auditory/Sensory Neurosciences and Sleep Medicine. As the auditory system is always “open, thus receiving information from the environment and the body itself (conscious and unconscious data), the incoming sensory information may alter sleep and waking physiology, and conversely, the sleeping brain.

This book draws information from evoked potentials, fMRI, PET, SPECT, lesions, and more.

• Contains new chapters on topics such as implanted deaf patients and sleep and tinnitus treatments during sleep
• Written for researchers and clinical practitioners in the auditory sciences, sleep medicine and sensory neuroscience

• Language: English
• Publisher: Academic Press
• Release date: Apr 20, 2018
• ISBN: 9780128104781

Ricardo Velluti

Dr. Velluti is a Free Professor at the Faculty of Medicine at U. ClAEH in Uruguay. He was previously a Professor of Physiology and Chairman of the Physiology Department, Universidad de la Republica, Montevideo, Uruguay. He has published over 63 publications and has authored two books dealing with sleep, the auditory system, and neurophysiology.

Book preview

standpoint.

Chapter 1

Brief Analysis of the Auditory System Organization and its Physiologic Basis

Abstract

The auditory system with its associated anatomical and functional complexity serves diverse processes, such as the discrimination of sound frequencies and intensities, sound source location in space, auditory learning, development of human language, auditory images in dreams, music, development of birds songs, i.e., communication in general. In this chapter a review of the known auditory ascending and descending systems is presented along with some new or less well known approaches.

Keywords

afferent; auditory nerve; auditory system; cochlea; efferent; imaging; reticular formation

The auditory system with its associated anatomical and functional complexity serves diverse processes, such as discrimination of sound frequencies and intensities, sound source location in space, auditory learning, development of human language and auditory ‘images’ in dreams, music and development of birds songs, that is, communication in general. In this chapter, a review of the known auditory ascending and descending systems are presented along with some new or not too well-known approaches.

The Afferent Ascending System

This complex system begins at the receptors in the cochlea followed by a wide upward expansion throughout the different nuclei, reticular formation, cerebellum and connections to the primary and secondary cortices. It is composed of several neuronal groups with profuse communication from the cochlea to the cortex.

Moreover, a nonclassical pathway assumed to branch off from classical path at the midbrain through connections from the central nucleus of the inferior colliculus (IC) (Moller and Rollins, 2002).

A diagram of the most important pathways and synaptic stations of the afferent auditory system is shown in Fig. 1.1 and a schematic one in Fig. 1.2. The first-order auditory neurons, with cell bodies located in Corti’s ganglion, send their axons centrally to form the auditory nerve, part of the VIIIth cranial pair. These nerve fibres synapse with the secondary neurons located centrally in different cochlear nucleus (CN) loci, in the medulla–pontine region. Let us bear in mind that 95% of the fibres that form the auditory nerve originate at the inner hair cells. The outer hair cells are innervated by only 5%, nonmyelinated afferent thin fibres.

Figure 1.1 General diagram of the ascending auditory pathways. These pathways are embedded in the brain, an important concept since it reflects the multiple communication pathways that may affect incoming auditory information.

Figure 1.2 Schematic view of the ascending and descending auditory systems. MGB, medial geniculate body; IC, inferior colliculus; CN, cochlear nucleus; SOC, superior olivary complex. Arrows indicate the ascending and descending paths. Modified from Terreros, G., Delano, P. 2016. Corticofugal modulation of peripheral auditory responses. Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile, Departamento de Otorrinolaringología, Hospital Clínico de, Santiago, Chile (Terreros and Delano, 2016).

The auditory pathway has been described using different methods of study throughout history: cell damage and degeneration, intracellular dyeing with tracers, deoxyglucose and by electrophysiological recording methods. By placing recording electrodes in various central nuclei bioelectrical responses, changes in the membrane potentials can be obtained from the auditory neurons that form the basis of evoked potentials measurable with a gross electrode. Evoked potentials, recorded in cats, shown in Fig. 1.3A, are examples of the averaged responses to a brief (click) sound stimuli. The differences between their shapes and, mainly, their latencies carefully reproduce the anatomical pathway, because activity evoked by a stimulus, first activates the receptors followed by the auditory nerve fibres, and subsequently the central nervous system (CNS), orderly ascending from nucleus to nucleus. Fig. 1.3B shows the short latency far-field potentials (brain-stem waves I–V). Recordings with a different time scale (50 ms) reveal the middle latency waves corresponding to the thalamic and cortical responses. A 500 ms time scale shows the full response including the late cortical