Immune cells and non-immune cells with immune function in mammalian cochleae

Publication date: Available online 20 December 2017
Source:Hearing Research
Author(s): Bo Hua Hu, Celia Zhang, Mitchell D. Frye
The cochlea has an immune environment dominated by macrophages under resting conditions. When stressed, circulating monocytes enter the cochlea. These immune mediators, along with cochlear resident cells, organize a complex defense response against pathological challenges. Since the cochlea has minimal exposure to pathogens, most inflammatory conditions in the cochlea are sterile. Although the immune response is initiated for the protection of the cochlea, off-target effects can cause collateral damage to cochlear cells. A better understanding of cochlear immune capacity and regulation would therefore lead to development of new therapeutic treatments. Over the past decade, there have been many advances in our understanding of cochlear immune capacity. In this review, we provide an update and overview of the cellular components of cochlear immune capacity with a focus on macrophages in mammalian cochleae. We describe the composition and distribution of immune cells in the cochlea and suggest that phenotypic and functional characteristics of macrophages have site-specific diversity. We also highlight the response of immune cells to acute and chronic stresses and comment on the potential function of immune cells in cochlear homeostasis and disease development. Finally, we briefly review potential roles for cochlear resident cells in the immune activities of the cochlea.



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Immune cells and non-immune cells with immune function in mammalian cochleae

Publication date: Available online 20 December 2017
Source:Hearing Research
Author(s): Bo Hua Hu, Celia Zhang, Mitchell D. Frye
The cochlea has an immune environment dominated by macrophages under resting conditions. When stressed, circulating monocytes enter the cochlea. These immune mediators, along with cochlear resident cells, organize a complex defense response against pathological challenges. Since the cochlea has minimal exposure to pathogens, most inflammatory conditions in the cochlea are sterile. Although the immune response is initiated for the protection of the cochlea, off-target effects can cause collateral damage to cochlear cells. A better understanding of cochlear immune capacity and regulation would therefore lead to development of new therapeutic treatments. Over the past decade, there have been many advances in our understanding of cochlear immune capacity. In this review, we provide an update and overview of the cellular components of cochlear immune capacity with a focus on macrophages in mammalian cochleae. We describe the composition and distribution of immune cells in the cochlea and suggest that phenotypic and functional characteristics of macrophages have site-specific diversity. We also highlight the response of immune cells to acute and chronic stresses and comment on the potential function of immune cells in cochlear homeostasis and disease development. Finally, we briefly review potential roles for cochlear resident cells in the immune activities of the cochlea.



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Immune cells and non-immune cells with immune function in mammalian cochleae

Publication date: Available online 20 December 2017
Source:Hearing Research
Author(s): Bo Hua Hu, Celia Zhang, Mitchell D. Frye
The cochlea has an immune environment dominated by macrophages under resting conditions. When stressed, circulating monocytes enter the cochlea. These immune mediators, along with cochlear resident cells, organize a complex defense response against pathological challenges. Since the cochlea has minimal exposure to pathogens, most inflammatory conditions in the cochlea are sterile. Although the immune response is initiated for the protection of the cochlea, off-target effects can cause collateral damage to cochlear cells. A better understanding of cochlear immune capacity and regulation would therefore lead to development of new therapeutic treatments. Over the past decade, there have been many advances in our understanding of cochlear immune capacity. In this review, we provide an update and overview of the cellular components of cochlear immune capacity with a focus on macrophages in mammalian cochleae. We describe the composition and distribution of immune cells in the cochlea and suggest that phenotypic and functional characteristics of macrophages have site-specific diversity. We also highlight the response of immune cells to acute and chronic stresses and comment on the potential function of immune cells in cochlear homeostasis and disease development. Finally, we briefly review potential roles for cochlear resident cells in the immune activities of the cochlea.



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Understanding Bilingual Word Learning: The Role of Phonotactic Probability and Phonological Neighborhood Density

Purpose

Previous research has shown that the language-learning mechanism is affected by bilingualism resulting in a novel word learning advantage for bilingual speakers. However, less is known about the factors that might influence this advantage. This article reports an investigation of 2 factors: phonotactic probability and phonological neighborhood density.

Method

Acquisition of 15 novel words varying in phonotactic probability and phonological neighborhood density was examined in high-proficiency, early onset, Mandarin–English bilinguals and English monolinguals.

Results

Both bilinguals and monolinguals demonstrated a significant effect of phonotactic probability and phonological neighborhood density. Novel word learning improved when the phonological neighborhood density was higher; in contrast, higher phonotactic probability resulted in worse learning. Although the bilingual speakers showed significantly better novel word learning than monolingual speakers, this did not interact with phonotactic probability and phonological neighborhood density manipulations.

Conclusion

Both bilingual and monolingual word learning abilities are constrained by the same learning mechanisms. However, bilingual advantages may be underpinned by more effective allocation of cognitive resources due to their dual language experience.

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A Multivariate Analytic Approach to the Differential Diagnosis of Apraxia of Speech

Purpose

Apraxia of speech (AOS) is a consequence of stroke that frequently co-occurs with aphasia. Its study is limited by difficulties with its perceptual evaluation and dissociation from co-occurring impairments. This study examined the classification accuracy of several acoustic measures for the differential diagnosis of AOS in a sample of stroke survivors.

Method

Fifty-seven individuals were included (mean age = 60.8 ± 10.4 years; 21 women, 36 men; mean months poststroke = 54.7 ± 46). Participants were grouped on the basis of speech/language testing as follows: AOS-Aphasia (n = 20), Aphasia Only (n = 24), and Stroke Control (n = 13). Normalized Pairwise Variability Index, proportion of distortion errors, voice onset time variability, and amplitude envelope modulation spectrum variables were obtained from connected speech samples. Measures were analyzed for group differences and entered into a linear discriminant analysis to predict diagnostic classification.

Results

Out-of-sample classification accuracy of all measures was over 90%. The envelope modulation spectrum variables had the greatest impact on classification when all measures were analyzed together.

Conclusions

This study contributes to efforts to identify objective acoustic measures that can facilitate the differential diagnosis of AOS. Results suggest that further study of these measures is warranted to determine the best predictors of AOS diagnosis.

Supplemental Materials

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Motivation to Address Self-Reported Hearing Problems in Adults With Normal Hearing Thresholds

Purpose

The purpose of this study was to compare the motivation to change in relation to hearing problems in adults with normal hearing thresholds but who report hearing problems and that of adults with a mild-to-moderate sensorineural hearing loss. Factors related to their motivation were also assessed.

Method

The motivation to change in relation to self-reported hearing problems was measured using the University of Rhode Island Change Assessment (McConnaughy, Prochaska, & Velicer, 1983). The relationship between objective and subjective measures and an adult's motivation was examined.

Results

The level of hearing handicap did not differ significantly between adults with normal hearing who reported problems hearing in background noise and adults who had a mild-to-moderate sensorineural hearing loss. Hearing handicap, personal distress, and minimization of hearing loss were factors significantly related to motivation. Age, degree of hearing loss, speech-in-noise scores, working memory, and extended high-frequency average thresholds were not significantly related to their motivation.

Conclusions

Adults with normal hearing thresholds but self-reported hearing problems had the same level of hearing handicap and were equally motivated to take action for their hearing problems as age-matched adults with a mild-to-moderate sensorineural hearing loss. Hearing handicap, personal distress, and minimization of hearing loss were most strongly correlated with an individual's motivation to change.

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Modeling Speech Level as a Function of Background Noise Level and Talker-to-Listener Distance for Talkers Wearing Hearing Protection Devices

Purpose

Studying the variations in speech levels with changing background noise level and talker-to-listener distance for talkers wearing hearing protection devices (HPDs) can aid in understanding communication in background noise.

Method

Speech was recorded using an intra-aural HPD from 12 different talkers at 5 different distances in 3 different noise conditions and 2 quiet conditions.

Results

This article proposes models that can predict the difference in speech level as a function of background noise level and talker-to-listener distance for occluded talkers. The proposed model complements the existing model presented by Pelegrín-García, Smits, Brunskog, and Jeong (2011) and expands on it by taking into account the effects of occlusion and background noise level on changes in speech sound level.

Conclusions

Three models of the relationship between vocal effort, background noise level, and talker-to-listener distance for talkers wearing HPDs are presented. The model with the best prediction intervals is a talker-dependent model that requires the users' unoccluded speech level at 10 m as a reference. A model describing the relationship between speech level, talker-to-listener distance, and background noise level for occluded talkers could eventually be incorporated with radio protocols to transmit verbal communication only to an intended set of listeners within a given spatial range—this range being dependent on the changes in speech level and background noise level.

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