Ultrastructural analysis of primary endings in deaf white cats: Morphologic alterations in endbulbs of held

Ryugo, David K.; Pongstaporn, Tan; Huchton, David M.; Niparko, John K.

doi:10.1002/(sici)1096-9861(19970825)385:2<230::aid-cne4>3.0.co;2-2

Cited by 133 publications

(133 citation statements)

References 68 publications

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“…It is interesting to note that in congenitally deaf white cats, degenerative alterations in individual auditory nerve synapses of the AVCN endbulbs of Held observed by Ryugo et al (1997) were largely reversed by 3 months of electrical stimulation via a cochlear implant (Ryugo et al, 2005). Specifically, in these early deafened animals (suggested to model Scheibe dysplasia), the authors reported reduced terminal branching of the endbulbs of Held, reduction in synaptic vesicle density, striking hypertrophy of the postsynaptic densities and enlargement of synapse size.…”

Section: Topography Of Auditory Nerve Projections To the Cochlear Nucmentioning

confidence: 99%

Factors influencing neurotrophic effects of electrical stimulation in the deafened developing auditory system

et al. 2008

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Research in animal models has demonstrated that electrical stimulation from a cochlear implant (CI) may help prevent degeneration of the cochlear spiral ganglion (SG) neurons after deafness. In cats deafened early in life, effective stimulation of the auditory nerve with complex signals for several months preserved a greater density of SG neurons in the stimulated cochleae as compared to the contralateral deafened ear. However, SG survival was still far from normal even with early intervention with an implant. Thus, pharmacologic agents and neurotrophic factors that might be used in combination with an implant are of great interest. Exogenous administration of GM1 ganglioside significantly reduces SG degeneration in deafened animals studied at 7-8 weeks of age, but after several months of stimulation, GM1-treated animals show only modestly better preservation of SG density compared to age-matched non-treated animals. A significant factor influencing neurotrophic effects in animal models is insertion trauma, which results in significant regional SG degeneration. Thus, an important goal is to further improve human CI electrode designs and insertion techniques to minimize trauma.Another important issue for studies of neurotrophic effects in the developing auditory system is the potential role of critical periods. Studies examining animals deafened at 30 days of age (rather than at birth) have explored whether a brief initial period of normal auditory experience affects the vulnerability of the SG or cochlear nucleus (CN) to auditory deprivation. Interestingly, SG survival in animals deafened at 30-days was not significantly different from age-matched neonatally deafened animals, but significant differences were observed in the central auditory system. CN volume was significantly closer to normal in the animals deafened at 30 days as compared to neonatally deafened animals. However, no difference was observed between the stimulated and contralateral CN volumes in either deafened group. Measurements of AVCN spherical cell somata showed that after later onset of deafness in the 30-day deafened group, mean cell size was significantly closer to normal than in the neonatally deafened group. Further, electrical stimulation elicited a significant increase in spherical cell size in the CN ipsilateral to the implant as compared to the contralateral CN in both deafened groups.Neuronal tracer studies have examined the primary afferent projections from the SG to the CN in neonatally deafened cats. CN projections exhibit a clear cochleotopic organization despite severe auditory deprivation from birth. However, when normalized for the smaller CN size after deafness, projections were 30-50% broader than normal. After unilateral electrical stimulation there was no difference between projections from the stimulated and non-stimulated ears. These findings suggest that early normal auditory experience may be essential for the normal development (or subsequent Publisher's Disclaimer: This is a PDF file of an unedited manuscript...

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Section: Topography Of Auditory Nerve Projections To the Cochlear Nucmentioning

confidence: 99%

Factors influencing neurotrophic effects of electrical stimulation in the deafened developing auditory system

et al. 2008

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“…Both congenital deafness and neonatal deafening cause structural abnormalities in the brainstem circuits that process ITD, including the endbulbs of Held in ventral cochlear nucleus (Ryugo et al 1997;Ryugo et al 1998;Lee et al 2003;Ryugo et al 2010) and inhibitory synapses onto MSO neurons (Tirko and Ryugo 2012). Chronic diotic stimulation using clinical CI processors largely reverses these changes (O'Neil et al 2010;Tirko and Ryugo 2012).…”

Section: Effect Of Deafness On Spontaneous Activitymentioning

confidence: 99%

Congenital and Prolonged Adult-Onset Deafness Cause Distinct Degradations in Neural ITD Coding with Bilateral Cochlear Implants

Hancock

Chung

Delgutte

2013

JARO

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Bilateral cochlear implant (CI) users perform poorly on tasks involving interaural time differences (ITD), which are critical for sound localization and speech reception in noise by normal-hearing listeners. ITD perception with bilateral CI is influenced by age at onset of deafness and duration of deafness. We previously showed that ITD coding in the auditory midbrain is degraded in congenitally deaf white cats (DWC) compared to acutely deafened cats (ADC) with normal auditory development (Hancock et al., J. Neurosci, 30:14068). To determine the relative importance of early onset of deafness and prolonged duration of deafness for abnormal ITD coding in DWC, we recorded from single units in the inferior colliculus of cats deafened as adults 6 months prior to experimentation (long-term deafened cats, LTDC) and compared neural ITD coding between the three deafness models. The incidence of ITD-sensitive neurons was similar in both groups with normal auditory development (LTDC and ADC), but significantly diminished in DWC. In contrast, both groups that experienced prolonged deafness (LTDC and DWC) had broad distributions of best ITDs around the midline, unlike the more focused distributions biased toward contralateral-leading ITDs present in both ADC and normalhearing animals. The lack of contralateral bias in LTDC and DWC results in reduced sensitivity to changes in ITD within the natural range. The finding that early onset of deafness more severely degrades neural ITD coding than prolonged duration of deafness argues for the importance of fitting deaf children with sound processors that provide reliable ITD cues at an early age.

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“…Studies in the congenitally deaf white cat reveal that synapses of auditory nerve endings are abnormal, such as between end bulbs of Held and spherical bushy cells [18][19][20], as well as between modified end bulbs and globular bushy cells [21]. In addition, the synaptic abnormalities are present at an early age (6 months) in the deaf white cat.…”

Section: Effects Of Symmetrical Profound Hearing Loss On the Auditorymentioning

confidence: 99%

Restoring hearing symmetry with two cochlear implants or one cochlear implant and a contralateral hearing aid

Firszt

Reeder²,

Skinner³

2008

JRRD

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Abstract-With today's technology and the demonstrated success of cochlear implantation, along with expanded candidacy criteria, the opportunity to provide optimal hearing to both ears for individuals with severe-to-profound hearing loss is greater than ever. This article reviews the advantages of binaural hearing and the disadvantages of hearing with only one ear or hearing with two ears with significantly different sound thresholds. A case study is presented that demonstrates the benefit of bimodal hearing (i.e., a cochlear implant [CI] in one ear and a contralateral hearing aid [HA]) in a nontraditional CI candidate with asymmetrical hearing thresholds. Then, selected studies in adult recipients who use a CI and contralateral HA or who use two CIs are summarized. The data overall demonstrate that bilateral CI recipients, traditional bimodal recipients, and nontraditional bimodal recipients experience substantial binaural hearing advantages, including improved speech recognition in noise, localization, and functional everyday communication. These results indicate that bilateral stimulation of the auditory system through a CI and contralateral HA or two CIs is beneficial and should become standard clinical practice.

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Ultrastructural analysis of primary endings in deaf white cats: Morphologic alterations in endbulbs of held

Cited by 133 publications

References 68 publications

Factors influencing neurotrophic effects of electrical stimulation in the deafened developing auditory system

Factors influencing neurotrophic effects of electrical stimulation in the deafened developing auditory system

Congenital and Prolonged Adult-Onset Deafness Cause Distinct Degradations in Neural ITD Coding with Bilateral Cochlear Implants

Restoring hearing symmetry with two cochlear implants or one cochlear implant and a contralateral hearing aid

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