1
|
EL KHOUSHT MM, DABBOUS AO, ABD-ELALEIM ZT, HAMDY HS. Effect of presbycusis on P3 auditory evoked potentials. OTORHINOLARYNGOLOGY 2022; 72. [DOI: 10.23736/s2724-6302.22.02404-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
|
2
|
Schormans AL, Typlt M, Allman BL. Adult-Onset Hearing Impairment Induces Layer-Specific Cortical Reorganization: Evidence of Crossmodal Plasticity and Central Gain Enhancement. Cereb Cortex 2020; 29:1875-1888. [PMID: 29668848 DOI: 10.1093/cercor/bhy067] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/22/2018] [Indexed: 11/14/2022] Open
Abstract
Adult-onset hearing impairment can lead to hyperactivity in the auditory pathway (i.e., central gain enhancement) as well as increased cortical responsiveness to nonauditory stimuli (i.e., crossmodal plasticity). However, it remained unclear to what extent hearing loss-induced hyperactivity is relayed beyond the auditory cortex, and thus, whether central gain enhancement competes or coexists with crossmodal plasticity throughout the distinct layers of the audiovisual cortex. To that end, we investigated the effects of partial hearing loss on laminar processing in the auditory, visual and audiovisual cortices of adult rats using extracellular electrophysiological recordings performed 2 weeks after loud noise exposure. Current-source density analyses revealed that central gain enhancement was not relayed to the audiovisual cortex (V2L), and was instead restricted to the granular layer of the higher order auditory area, AuD. In contrast, crossmodal plasticity was evident across multiple cortical layers within V2L, and also manifested in AuD. Surprisingly, despite this coexistence of central gain enhancement and crossmodal plasticity, noise exposure did not disrupt the responsiveness of these neighboring cortical regions to combined audiovisual stimuli. Overall, we have shown for the first time that adult-onset hearing impairment causes a complex assortment of intramodal and crossmodal changes across the layers of higher order sensory cortices.
Collapse
Affiliation(s)
- Ashley L Schormans
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Marei Typlt
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Brian L Allman
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| |
Collapse
|
3
|
Hatano M, Kelly JB, Zhang H. Area-dependent change of response in the rat's inferior colliculus to intracochlear electrical stimulation following neonatal cochlear damage. Sci Rep 2019; 9:5643. [PMID: 30948747 PMCID: PMC6449351 DOI: 10.1038/s41598-019-41955-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 03/19/2019] [Indexed: 12/04/2022] Open
Abstract
To understand brain changes caused by auditory sensory deprivation, we recorded local-field potentials in the inferior colliculus of young adult rats with neonatal cochlear damage produced by systemic injections of amikacin. The responses were elicited by electrical stimulation of the entire cochlea and recorded at various locations along a dorsolateral-ventromedial axis of the inferior colliculus. We found that hair cells were completely destroyed and spiral ganglion neurons were severely damaged in the basal cochleae of amikacin-treated animals. Hair cells as well as spiral ganglion neurons were damaged also in the middle and apical areas of the cochlea, with the damage being greater in the middle than the apical area. Amplitudes of local-field potentials were reduced in the ventromedial inferior colliculus, but enhanced in the dorsolateral inferior colliculus. Latencies of responses were increased over the entire structure. The enhancement of responses in the dorsolateral inferior colliculus was in contrast with the damage of hair cells and spiral ganglion cells in the apical part of the cochlea. This contrast along with the overall increase of latencies suggests that early cochlear damage can alter neural mechanisms within the inferior colliculus and/or the inputs to this midbrain structure.
Collapse
Affiliation(s)
- Miyako Hatano
- Department of Otolaryngology-Head and Neck Surgery, Kanazawa University, Kanazawa, 920-8640, Ishikawa, Japan.
| | - Jack B Kelly
- Department of Neuroscience, Carleton University, Ottawa, Ontario, K1S 5B6, Canada
| | - Huiming Zhang
- Department of Biological Sciences, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
| |
Collapse
|
4
|
Tillein J, Hartmann R, Kral A. Electric-acoustic interactions in the hearing cochlea: Single fiber recordings. Hear Res 2015; 322:112-26. [DOI: 10.1016/j.heares.2014.09.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Revised: 08/30/2014] [Accepted: 09/22/2014] [Indexed: 10/24/2022]
|
5
|
Auerbach BD, Rodrigues PV, Salvi RJ. Central gain control in tinnitus and hyperacusis. Front Neurol 2014; 5:206. [PMID: 25386157 PMCID: PMC4208401 DOI: 10.3389/fneur.2014.00206] [Citation(s) in RCA: 259] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 09/30/2014] [Indexed: 12/02/2022] Open
Abstract
Sensorineural hearing loss induced by noise or ototoxic drug exposure reduces the neural activity transmitted from the cochlea to the central auditory system. Despite a reduced cochlear output, neural activity from more central auditory structures is paradoxically enhanced at suprathreshold intensities. This compensatory increase in the central auditory activity in response to the loss of sensory input is referred to as central gain enhancement. Enhanced central gain is hypothesized to be a potential mechanism that gives rise to hyperacusis and tinnitus, two debilitating auditory perceptual disorders that afflict millions of individuals. This review will examine the evidence for gain enhancement in the central auditory system in response to cochlear damage. Further, it will address the potential cellular and molecular mechanisms underlying this enhancement and discuss the contribution of central gain enhancement to tinnitus and hyperacusis. Current evidence suggests that multiple mechanisms with distinct temporal and spectral profiles are likely to contribute to central gain enhancement. Dissecting the contributions of these different mechanisms at different levels of the central auditory system is essential for elucidating the role of central gain enhancement in tinnitus and hyperacusis and, most importantly, the development of novel treatments for these disorders.
Collapse
Affiliation(s)
- Benjamin D Auerbach
- Department of Communicative Disorders and Sciences, Center for Hearing and Deafness, University at Buffalo, The State University of New York , Buffalo, NY , USA
| | - Paulo V Rodrigues
- Department of Communicative Disorders and Sciences, Center for Hearing and Deafness, University at Buffalo, The State University of New York , Buffalo, NY , USA
| | - Richard J Salvi
- Department of Communicative Disorders and Sciences, Center for Hearing and Deafness, University at Buffalo, The State University of New York , Buffalo, NY , USA
| |
Collapse
|
6
|
Abstract
The success of modern neural prostheses is dependent on a complex interplay between the devices' hardware and software and the dynamic environment in which the devices operate: the patient's body or 'wetware'. Over 120 000 severe/profoundly deaf individuals presently receive information enabling auditory awareness and speech perception from cochlear implants. The cochlear implant therefore provides a useful case study for a review of the complex interactions between hardware, software and wetware, and of the important role of the dynamic nature of wetware. In the case of neural prostheses, the most critical component of that wetware is the central nervous system. This paper will examine the evidence of changes in the central auditory system that contribute to changes in performance with a cochlear implant, and discuss how these changes relate to electrophysiological and functional imaging studies in humans. The relationship between the human data and evidence from animals of the remarkable capacity for plastic change of the central auditory system, even into adulthood, will then be examined. Finally, we will discuss the role of brain plasticity in neural prostheses in general.
Collapse
Affiliation(s)
- James B Fallon
- Bionic Ear Institute, 384-388 Albert Street, East Melbourne, VIC 3002, Australia.
| | | | | |
Collapse
|
7
|
Fallon JB, Irvine DRF, Shepherd RK. Cochlear implants and brain plasticity. Hear Res 2008; 238:110-7. [PMID: 17910997 PMCID: PMC2361156 DOI: 10.1016/j.heares.2007.08.004] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Revised: 08/15/2007] [Accepted: 08/15/2007] [Indexed: 01/13/2023]
Abstract
Cochlear implants have been implanted in over 110,000 deaf adults and children worldwide and provide these patients with important auditory cues necessary for auditory awareness and speech perception via electrical stimulation of the auditory nerve (AN). In 1942, Woolsey and Walzl presented the first report of cortical responses to localised electrical stimulation of different sectors of the AN in normal hearing cats, and established the cochleotopic organization of the projections to primary auditory cortex. Subsequently, individual cortical neurons in normal hearing animals have been shown to have well characterized input-output functions for electrical stimulation and decreasing response latencies with increasing stimulus strength. However, the central auditory system is not immutable, and has a remarkable capacity for plastic change, even into adulthood, as a result of changes in afferent input. This capacity for change is likely to contribute to the ongoing clinical improvements observed in speech perception for cochlear implant users. This review examines the evidence for changes of the response properties of neurons in, and consequently the functional organization of, the central auditory system produced by chronic, behaviourally relevant, electrical stimulation of the AN in profoundly deaf humans and animals.
Collapse
Affiliation(s)
- James B Fallon
- Bionic Ear Institute, 384-388 Albert Street, East Melbourne, VIC 3002, Australia.
| | | | | |
Collapse
|
8
|
Jeng FC, Abbas PJ, Brown CJ, Miller CA, Nourski KV, Robinson BK. Electrically evoked auditory steady-state responses in Guinea pigs. Audiol Neurootol 2006; 12:101-12. [PMID: 17264473 DOI: 10.1159/000097796] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Accepted: 09/13/2006] [Indexed: 11/19/2022] Open
Abstract
Most cochlear implant systems available today provide the user with information about the envelope of the speech signal. The goal of this study was to explore the feasibility of recording electrically evoked auditory steady-state response (ESSR) and in particular to evaluate the degree to which the response recorded using electrical stimulation could be separated from stimulus artifact. Sinusoidally amplitude-modulated electrical stimuli with alternating polarities were used to elicit the response in adult guinea pigs. Separation of the stimulus artifact from evoked neural responses was achieved by summing alternating polarity responses or by using spectral analysis techniques. The recorded response exhibited physiological response properties including a pattern of nonlinear growth and their abolishment following euthanasia or administration of tetrodotoxin. These findings demonstrate that the ESSR is a response generated by the auditory system and can be separated from electrical stimulus artifact. As it is evoked by a stimulus that shares important features of cochlear implant stimulation, this evoked potential may be useful in either clinical or basic research efforts.
Collapse
Affiliation(s)
- Fuh-Cherng Jeng
- Department of Speech Pathology and Audiology, Department of Otolaryngology--HNS, University of Iowa, Iowa City, Iowa, USA.
| | | | | | | | | | | |
Collapse
|
9
|
Kral A, Tillein J, Heid S, Hartmann R, Klinke R. Postnatal Cortical Development in Congenital Auditory Deprivation. Cereb Cortex 2004; 15:552-62. [PMID: 15319310 DOI: 10.1093/cercor/bhh156] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The study investigates early postnatal development of local field potentials (LFPs) in the primary auditory cortex of hearing and congenitally deaf cats. In hearing cats, LFPs elicited by electrical intracochlear stimulation demonstrated developmental changes in mid-latency range, including reductions in peak and onset latencies of individual waves and a maturation of their shape and latencies during the first 2 months of life. In long latency range (>80 ms), the P(1)/N(1) response appeared after the fourth week of life and further increased in amplitude and decreased in latency, reaching mature shapes between the fourth and sixth months after birth (p.n.). Cortical activated areas became increasingly smaller during the first 3 months of life, reaching mature values at the fourth month p.n. The layer-specific pattern of synaptic activity matured 4 months p.n. In congenitally deaf cats, the developmental pattern was different. The lowest cortical LFP thresholds were significantly smaller than in hearing controls, demonstrating a "hypersensitivity" to sensory inputs. The development of N(b) waves was delayed and altered and the long latency responses became smaller than in controls at the second and third months. The activated areas remained smaller than in controls until the third month, then they increased rapidly and exceeded the activated areas of age-matched controls. From the fourth month on, the activated areas decreased again and smaller synaptic currents were found in deaf cats than in controls. The presented data demonstrate that functional development of the auditory cortex critically depends on auditory experience.
Collapse
Affiliation(s)
- A Kral
- Institute of Sensory Physiology & Neurophysiology, J.W.Goethe University School of Medicine, Frankfurt am Main, Germany.
| | | | | | | | | |
Collapse
|
10
|
Hartmann R, Kral A. Central Responses to Electrical Stimulation. COCHLEAR IMPLANTS: AUDITORY PROSTHESES AND ELECTRIC HEARING 2004. [DOI: 10.1007/978-0-387-22585-2_6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
11
|
Takahashi H, Ejiri T, Nakao M, Nakamura N, Kaga K, Hervé T. Microelectrode array on folding polyimide ribbon for epidural mapping of functional evoked potentials. IEEE Trans Biomed Eng 2003; 50:510-6. [PMID: 12723063 DOI: 10.1109/tbme.2003.809483] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This paper describes a flexible polyimide microelectrode ribbon with a bending structure for epidural recording. Bending the ribbon establishes good electro-mechanical contact of the electrodes to the cortex. Impedance spectroscopy and noise measurements in vitro were used to characterize the electrodes. Our in vivo experiments then successfully achieved synchronized neuronal activity and evoked potential patterns useful for understanding brain function and for finding cortical function.
Collapse
Affiliation(s)
- Hirokazu Takahashi
- Department of Engineering Synthesis, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
| | | | | | | | | | | |
Collapse
|
12
|
Syka J. Plastic changes in the central auditory system after hearing loss, restoration of function, and during learning. Physiol Rev 2002; 82:601-36. [PMID: 12087130 DOI: 10.1152/physrev.00002.2002] [Citation(s) in RCA: 271] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Traditionally the auditory system was considered a hard-wired sensory system; this view has been challenged in recent years in light of the plasticity of other sensory systems, particularly the visual and somatosensory systems. Practical experience in clinical audiology together with the use of prosthetic devices, such as cochlear implants, contributed significantly to the present view on the plasticity of the central auditory system, which was originally based on data obtained in animal experiments. The loss of auditory receptors, the hair cells, results in profound changes in the structure and function of the central auditory system, typically demonstrated by a reorganization of the projection maps in the auditory cortex. These plastic changes occur not only as a consequence of mechanical lesions of the cochlea or biochemical lesions of the hair cells by ototoxic drugs, but also as a consequence of the loss of hair cells in connection with aging or noise exposure. In light of the aging world population and the increasing amount of noise in the modern world, understanding the plasticity of the central auditory system has its practical consequences and urgency. In most of these situations, a common denominator of central plastic changes is a deterioration of inhibition in the subcortical auditory nuclei and the auditory cortex. In addition to the processes that are elicited by decreased or lost receptor function, the function of nerve cells in the adult central auditory system may dynamically change in the process of learning. A better understanding of the plastic changes in the central auditory system after sensory deafferentation, sensory stimulation, and learning may contribute significantly to improvement in the rehabilitation of damaged or lost auditory function and consequently to improved speech processing and production.
Collapse
Affiliation(s)
- Josef Syka
- Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
| |
Collapse
|
13
|
Abstract
This chapter describes the development of two implantable prosthetic neurostimulators which, in the last 20 years, have revolutionised the management of severe-to-profound sensorineural deafness. We have witnessed their rapid evolution from the realms of esoteric laboratory abstraction, with many critics and little perceived clinical use, to a routine treatment which is safe, effective and, indeed, cost effective. It is one of the great triumphs of biomedical and surgical collaboration, and is without any doubt the greatest ever advance in the treatment of deafness.
Collapse
Affiliation(s)
- James B. Fallon
- Bionic Ear Institute, 384-388 Albert Street, East Melbourne, VIC 3002, Australia
- Department of Otolaryngology, University of Melbourne, VIC 3002, Australia
| | - Dexter R. F. Irvine
- Bionic Ear Institute, 384-388 Albert Street, East Melbourne, VIC 3002, Australia
- School of Psychology, Psychiatry, and Psychological Medicine, Faculty of Medicine, Nursing, and Health Sciences, Monash University, VIC 3800, Australia
| | - Robert K. Shepherd
- Bionic Ear Institute, 384-388 Albert Street, East Melbourne, VIC 3002, Australia
- Department of Otolaryngology, University of Melbourne, VIC 3002, Australia
| |
Collapse
|
14
|
Kral A, Hartmann R, Tillein J, Heid S, Klinke R. Congenital auditory deprivation reduces synaptic activity within the auditory cortex in a layer-specific manner. Cereb Cortex 2000; 10:714-26. [PMID: 10906318 DOI: 10.1093/cercor/10.7.714] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The present study investigates the functional deficits of naive auditory cortices in adult congenitally deaf cats. For this purpose, their auditory system was stimulated electrically using cochlear implants. Synaptic currents in cortical layers were revealed using current source density analyses. They were compared with synaptic currents found in electrically stimulated hearing cats. The naive auditory cortex showed significant deficits in synaptic activity in infragranular cortical layers. Furthermore, there was also a deficit of synaptic activities at longer latencies (>30 ms). The 'cortical column' was not activated in the well-defined sequence found in normal hearing cats. These results demonstrate functional deficits as a consequence of congenital auditory deprivation. Similar deficits are likely in congenitally deaf children.
Collapse
Affiliation(s)
- A Kral
- Physiologisches Institut III, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
| | | | | | | | | |
Collapse
|
15
|
Abstract
Neuronal cells are unique within the organism. In addition to forming long-distance connections with other nerve cells and non-neuronal targets, they lose the ability to regenerate their neurites and to divide during maturation. Consequently, external violations like trauma or disease frequently lead to their disappearance and replacement by non-neuronal, and thus not properly functioning cells. The advent of microtechnology and construction of artificial implants prompted to create particular devices for specialised regions of the nervous system, in order to compensate for the loss of function. The scope of the present work is to review the current devices in connection with their applicability and functional perspectives. (1) Successful implants like the cochlea implant and peripherally implantable stimulators are discussed. (2) Less developed and not yet applicable devices like retinal or cortical implants are introduced, with particular emphasis given to the reasons for their failure to replace very complex functions like vision. (3) Material research is presented both from the technological aspect and from their biocompatibility as prerequisite of any implantation. (4) Finally, basic studies are presented, which deal with methods of shaping the implants, procedures of testing biocompatibility and modification of improving the interfaces between a technical device and the biological environment. The review ends by pointing to future perspectives in neuroimplantation and restoration of interrupted neuronal pathways.
Collapse
Affiliation(s)
- P Heiduschka
- University Eye Hospital Münster, Experimental Ophthalmology, Germany
| | | |
Collapse
|
16
|
Hartmann R, Shepherd RK, Heid S, Klinke R. Response of the primary auditory cortex to electrical stimulation of the auditory nerve in the congenitally deaf white cat. Hear Res 1997; 112:115-33. [PMID: 9367234 DOI: 10.1016/s0378-5955(97)00114-7] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Neural activity plays an important role in the development and maintenance of sensory pathways. However, while there is considerable experience using cochlear implants in both congenitally deaf adults and children, little is known of the effects of a hearing loss on the development of the auditory cortex. In the present study, cortical evoked potentials, field potentials, and multi- and single-unit activity evoked by electrical stimulation of the auditory nerve were used to study the functional organisation of the auditory cortex in the adult congenitally deaf white cat. The absence of click-evoked auditory brainstem responses during the first weeks of life demonstrated that these animals had no auditory experience. Under barbiturate anaesthesia, cortical potentials could be recorded from the contralateral auditory cortex in response to bipolar electrical stimulation of the cochlea in spite of total auditory deprivation. Threshold, morphology and latency of the evoked potentials varied with the location of the recording electrode, with response latency varying from 10 to 20 ms. There was evidence of threshold shifts with site of the cochlear stimulation in accordance with the known cochleotopic organisation of AI. Thresholds also varied with the configuration of the stimulating electrodes in accordance with changes previously observed in normal hearing animals. Single-unit recordings exhibited properties similar to the evoked potentials. Increasing stimulus intensity resulted in an increase in spike rate and a decrease in latency to a minimum of approximately 8 ms, consistent with latencies recorded in AI of previously normal animals (Raggio and Schreiner, 1994). Single-unit thresholds also varied with the configuration of the stimulating electrodes. Strongly driven responses were followed by a suppression of spontaneous activity. Even at saturation intensities the degree of synchronisation was less than observed when recording from auditory brainstem nuclei. Taken together, in these auditory deprived animals basic response properties of the auditory cortex of the congenitally deaf white cat appear similar to those reported in normal hearing animals in response to electrical stimulation of the auditory nerve. In addition, it seems that the auditory cortex retains at least some rudimentary level of cochleotopic organisation.
Collapse
Affiliation(s)
- R Hartmann
- Physiologisches Institut III der J.W. Goethe-Universität, Frankfurt/M, Germany.
| | | | | | | |
Collapse
|
17
|
Abstract
The auditory middle latency response (MLR) seems to have a relatively long developmental time course, extending through the first decade of life. Characteristics of each MLR component change developmentally not only with respect to waveform morphology but also with respect to response reliability, dependence on awareness state, and stimulus rate. Both human and animal studies indicate that these complex changes may be a result of multiple generating systems that show multiple time courses of development. This framework has practical ramifications in that clinical and research studies of MLR in young children must take into account the development sequence. Furthermore, it cannot be assumed a priori that research results obtained from adults will apply to young children. The complexity of the process raises intriguing questions regarding the functional development of auditory perception.
Collapse
|