Hearing Controls Research Articles

Sensitive period for white‐matter connectivity of superior temporal cortex in deaf people

Previous studies have shown that white matter in the deaf brain changes due to hearing loss. However, how white-matter development is influenced by early hearing experience of deaf people is still unknown. Using diffusion tensor imaging and tract-based spatial statistics, we compared white-matter structures among three groups of subjects including 60 congenitally deaf individuals, 36 acquired deaf (AD) individuals, and 38 sex- and age-matched hearing controls (HC). The result showed that the deaf individuals had significantly reduced fractional anisotropy (FA) values in bilateral superior temporal cortex and the splenium of corpus callosum compared to HC. The reduction of FA values in acquired deafness correlated with onset age of deafness, but not the duration of deafness. To explore the underlying mechanism of FA changes in the deaf groups, we further analyzed radial and axial diffusivities and found that (1) the reduced FA values in deaf individuals compared to HC is primarily driven by higher radial diffusivity values and (2) in the AD, higher radial diffusivity was correlated with earlier onset age of deafness, but not the duration of deafness. These findings imply that early sensory experience is critical for the growth of fiber myelination, and anatomical reorganization following auditory deprivation is sensitive to early plasticity in the brain.

Somatosensory and visual crossmodal plasticity in the anterior auditory field of early-deaf cats

It is well known that the post-natal loss of sensory input in one modality can result in crossmodal reorganization of the deprived cortical areas, but deafness fails to induce crossmodal effects in cat primary auditory cortex (A1). Because the core auditory regions (A1, and anterior auditory field AAF) are arranged as separate, parallel processors, it cannot be assumed that early-deafness affects one in the same manner as the other. The present experiments were conducted to determine if crossmodal effects occur in the anterior auditory field (AAF). Using mature cats (n = 3), ototoxically deafened postnatally, single-unit recordings were made in the gyral and sulcal portions of the AAF. In contrast to the auditory responsivity found in the hearing controls, none of the neurons in early-deafened AAF were activated by auditory stimulation. Instead, the majority (78%) were activated by somatosensory cues, while fewer were driven by visual stimulation (44%; values include unisensory and bimodal neurons). Somatosensory responses could be activated from all locations on the body surface but most often occurred on the head, were often bilateral (e.g., occupied portions of both sides of the body), and were primarily excited by low-threshold hair receptors. Visual receptive fields were large, collectively represented the contralateral visual field, and exhibited conventional response properties such as movement direction and velocity preferences. These results indicate that, following post-natal deafness, both somatosensory and visual modalities participate in crossmodal reinnervation of the AAF, consistent with the growing literature that documents deafness-induced crossmodal plasticity outside A1.

Exogenous Material in the Inner Ear of the Adult Port Jackson Shark, Heterodontus Portusjacksoni (Elasmbranchii)

Previous studies have suggested that the inner ear of some benthic species of elasmobranchs contain only exogenous material within their otoconial organs, a unique feature within vertebrates. However, these examinations have not accounted for the possibility of otoconial degeneration or used modern experimental methods to identify the materials present. Both of these issues are addressed in this study using inner ear samples from the adult Port Jackson shark, Heterodontus portusjacksoni. A comparison of the otoconial mass in fixed specimens over short and medium time scales reveals that over those timescales the degeneration of calcium carbonate-based otoconia does not occur and confirms that calcium carbonate-based otoconia are not found within the otoconial organs of H. portusjacksoni. Additionally, microanalysis of the chemical composition and ultrastructure of the otoconial mass using energy dispersive X-ray microanalysis and scanning electron microscopy confirms that the entire otoconial mass is comprised of exogenous silicon dioxide particles, bound within a carbon matrix. This exogenous material is suggested to play an equivalent role to the otoconia found in other species of elasmobranchs, and allows both hearing and vestibular control to occur in benthic sharks that spend their lives foraging within a sandy substrate.

Functional Evaluation of GJB2 Variants in Nonsyndromic Hearing Loss

Mutations in the gap junction β2 (GJB2) gene, encoding the connexin26 (CX26) protein, are the most common cause of non-syndromic hearing loss (HL) in many populations. In the East Asian population, two variants, p.V27I (c.79G>A) and p.E114G (c.341G>A), are considered benign polymorphisms since these variants have been identified in both HL patients and normal hearing controls. However, some studies have postulated that homozygotes carrying both p.V27I and p.E114G variants could cause HL. To elucidate possible roles of these variants, we used in vitro approaches to directly assess the pathogenicity of four haplotypes generated by the two polymorphisms: VE (wild type), I*E (p.V27I variant only), VG* (p.E114G variant only), I*G* (both variants). In biochemical coupling assays, the gap junctions (GJs) composed of VG* and I*G* types displayed defective channel activities compared with those of VE wild types or I*E types, which showed normal channel activities. Interestingly, the defect in hemichannel activity was a bit less severe in I*G* type than VG* type, suggesting that I* variant (p.V27I) may compensate for the deleterious effect of G* variant (p.E114G) in hemichannel activities. Our population studies using 412 Korean individuals showed that I*G* type was detected at around 20% in both HL patients and normal controls, suggesting that I*G* type may not be a pathogenic polymorphism. In contrast, VG* type was very rare (3/824) and detected only in HL patients, suggesting that VG* homozygotes (VG*/VG*) or compound heterozygotes carrying VG* type with other mutations may cause HL.

Role of Connexin 32 (Cx32) and Hearing Loss In Charcot‐Marie‐Tooth Syndrome (CMTS)

Objective: Evaluate the role of Cx32 and hearing loss associated with Charcot-Marie-Tooth syndrome using a Cx32 knockout (KO) mice model. Study Design: Scientific Research. Methods: Cx32 knock-out mice (KO) were compared to CBA normal hearing controls and Cx32 wild type (WT) mice to evaluate inner ear development using epifluorescent microscopy and auditory performance using auditory brainstem response (ABR) testing at approximately 3, 6, and 12 months of age. Distribution of Cx32 was compared relative to Cx26 and Cx30 using immunofluorescent staining and epifluorescent microscopy. Results: Cx32KO mice showed greater hearing loss compared to CBA controls by 4.5-6 months of age (thresholds: 51.75 +/10.3 dB verse 40 +/5 dB, respectively, p=0.0001). The difference became more pronounced with aging (13 month CBA control threshold: 41.7 +/2.9 dB verses 10-11 month Cx32KO threshold: 63.6 +/14.2 dB, p<0.0001). Distribution of Cx32 differed from Cx26 and Cx30. Cx26 and Cx30 were prominent in the spiral lamina, supporter cell region, and lateral connective tissue in the CBA, Cx32WT, and Cx32KO mice. In contrast, Cx32 showed minimal presence and solely in the supporter cell region in both the CBA and Cx32WT mice while absent in the Cx32KO mice. Conclusion: While Cx32KO mice showed normal cochlear architectural morphology, Cx32 deletion results in earlier hearing loss. This may suggest a cochlear endolymphatic dysregulation due to its location in the supporter cell region as the cause of hearing loss in CMTS, not auditory neuropathy, as Cx32 was not present in the spiral ganglion. Cx32KO mice may serve to study hearing loss in CMTS.

Children with cochlear implants and developmental disabilities: A language skills study with developmentally matched hearing peers

The number of children receiving cochlear implants (CIs) with significant disabilities in addition to their deafness has increased substantially. Unfortunately, children with additional disabilities receiving CIs have largely been excluded from studies on cochlear implant outcomes. Thus limited data exists on outcomes in this population to guide pre-implant counseling for anticipated benefits. The study objectives were: (1) evaluate differences in post-cochlear implant language skills between children with cochlear implants and developmental disabilities and age/cognitively matched controls; (2) quantify possible discrepancies between language level and cognitive level. Fifteen children with a developmental disability who received a CI were matched 1:1 on nonverbal cognitive ability and age to hearing controls. Language was evaluated using Preschool Language Scale-IV and reported as language quotients. Multivariable mixed models for matched pairs analyzed differences in language levels between groups. No significant differences were seen between CI and control groups regarding insurance, maternal education, or family income level. Results of the multivariable models indicated that compared to matched controls, the CI group had significantly lower mean receptive (24.6 points, p=0.002) and mean expressive (21.9 points, p=0.001) language quotients after controlling for confounders such as number of therapies and weekly hours in therapy. Significant discrepancies between language level and cognitive level were seen among CI participants only. Compared to age- and cognitively matched controls, children with CIs had significantly lower language levels with delays disproportionate to their cognitive potential. Mechanisms behind this performance-functional gap need to be understood to deliver appropriate intervention strategies for this special population.

Prevalence of the GJB2 IVS1+1G &gt;A mutation in Chinese hearing loss patients with monoallelic pathogenic mutation in the coding region of GJB2

BackgroundMutations in the GJB2 gene are the most common cause of nonsyndromic recessive hearing loss in China. In about 6% of Chinese patients with severe to profound sensorineural hearing impairment, only monoallelic GJB2 mutations known to be either recessive or of unclear pathogenicity have been identified. This paper reports the prevalence of the GJB2 IVS1+1G>A mutation in a population of Chinese hearing loss patients with monoallelic pathogenic mutation in the coding region of GJB2.MethodsTwo hundred and twelve patients, screened from 7133 cases of nonsyndromic hearing loss in China, with monoallelic mutation (mainly frameshift and nonsense mutation) in the coding region of GJB2 were examined for the GJB2 IVS1+1G>A mutation and mutations in the promoter region of this gene. Two hundred and sixty-two nonsyndromic hearing loss patients without GJB2 mutation and 105 controls with normal hearing were also tested for the GJB2 IVS1+1G>A mutation by sequencing.ResultsFour patients with monoallelic mutation in the coding region of GJB2 were found carrying the GJB2 IVS1+1G>A mutation on the opposite allele. One patient with the GJB2 c.235delC mutation carried one variant, -3175 C>T, in exon 1 of GJB2. Neither GJB2 IVS1+1G>A mutation nor any variant in exon 1 of GJB2 was found in the 262 nonsyndromic hearing loss patients without GJB2 mutation or in the 105 normal hearing controls.ConclusionTesting for the GJB2 IVS 1+1 G to A mutation explained deafness in 1.89% of Chinese GJB2 monoallelic patients, and it should be included in routine testing of patients with GJB2 monoallelic pathogenic mutation.

Deaf and hearing children: a comparison of peripheral vision development

This study investigated peripheral vision (at least 30° eccentric to fixation) development in profoundly deaf children without cochlear implantation, and compared this to age-matched hearing controls as well as to deaf and hearing adult data. Deaf and hearing children between the ages of 5 and 15 years were assessed using a new, specifically paediatric designed method of static perimetry. The deaf group (N = 25) were 14 females and 11 males, mean age 9.92 years (range 5-15 years). The hearing group (N = 64) were 34 females, 30 males, mean age 9.13 years (range 5-15 years). All participants had good visual acuity in both eyes (< 0.200 LogMAR). Accuracy of detection and reaction time to briefly presented LED stimuli of three light intensities, at eccentricities between 30° and 85° were measured while fixation was maintained to a central target. The study found reduced peripheral vision in deaf children between 5 and 10 years of age. Deaf children (aged 5-10 years) showed slower reaction times to all stimuli and reduced ability to detect and accurately report dim stimuli in the far periphery. Deaf children performed equally to hearing children aged 11-12 years. Deaf adolescents aged 13-15 years demonstrated faster reaction times to all peripheral stimuli in comparison to hearing controls. Adolescent results were consistent with deaf and hearing adult performances wherein deaf adults also showed significantly faster reaction times than hearing controls. Peripheral vision performance on this task was found to reach adult-like levels of maturity in deaf and hearing children, both in reaction time and accuracy of detection at the age of 11-12 years.

Neuroanatomical changes due to hearing loss and chronic tinnitus: A combined VBM and DTI study

Subjective tinnitus is the perception of sound in the absence of an external source. Tinnitus is often accompanied by hearing loss but not everyone with hearing loss experiences tinnitus. We examined neuroanatomical alterations associated with hearing loss and tinnitus in three groups of subjects: those with hearing loss with tinnitus, those with hearing loss without tinnitus and normal hearing controls without tinnitus. To examine changes in gray matter we used structural MRI scans and voxel-based morphometry (VBM) and to identify changes in white matter tract orientation we used diffusion tensor imaging (DTI). A major finding of our study was that there were both gray and white matter changes in the vicinity of the auditory cortex for subjects with hearing loss alone relative to those with tinnitus and those with normal hearing. We did not find significant changes in gray or white matter in subjects with tinnitus and hearing loss compared to normal hearing controls. VBM analysis revealed that individuals with hearing loss without tinnitus had gray matter decreases in anterior cingulate and superior and medial frontal gyri relative to those with hearing loss and tinnitus. Region-of-interest analysis revealed additional decreases in superior temporal gyrus for the hearing loss group compared to the tinnitus group. Investigating effects of hearing loss alone, we found gray matter decreases in superior and medial frontal gyri in participants with hearing loss compared to normal hearing controls. DTI analysis showed decreases in fractional anisotropy values in the right superior and inferior longitudinal fasciculi, corticospinal tract, inferior fronto-occipital tract, superior occipital fasciculus, and anterior thalamic radiation for the hearing loss group relative to normal hearing controls. In attempting to dissociate the effect of tinnitus from hearing loss, we observed that hearing loss rather than tinnitus had the greatest influence on gray and white matter alterations.

The role of perceptual learning in emotional vocalizations.

Vocalizations like screams and laughs are used to communicate affective states, but what acoustic cues in these signals require vocal learning and which ones are innate? This study investigated the role of auditory learning in the production of non‐verbal emotional vocalizations by examining the vocalizations produced by people born deaf. Recordings were made of congenitally deaf Dutch individuals and matched hearing controls, who produced non‐verbal vocalizations of a range of negative and positive emotions. Perception was examined in a forced‐choice task with hearing Dutch listeners (n = 25), and judgments were analyzed together with acoustic cues, including envelope, pitch, and spectral measures. Considerable variability was found across emotions and acoustic cues, and the two types of information were related for a sub‐set of the emotion categories. These results suggest that auditory learning is less important for the acquisition of certain types of vocalizations than for others (particularly amusement and relief), and they also point to a less central role for auditory learning of some acoustic features in affective non‐verbal vocalizations. The implications of these results for models of vocal emotional communication are discussed.

‘You sometimes get more than you ask for’: responses in referential communication between children and adolescents with cochlear implant and hearing peers

This study investigates responses to requests for clarification in conversations between children/adolescents with cochlear implant (CI) and normally hearing peers. Earlier studies have interpreted a more frequent use of requests of confirmation (yes/no interrogatives) in the CI group as a conversational strategy used to prevent communication breakdowns and control the development of the conversation. This study provides a continuation of this line of research, now focusing on responses to requests for clarification. The aim was to examine the type and distribution of responses to requests for clarification in a referential communication task. In addition, we analysed the compliance between the type of response and the type of request as a measure of mutual adaptation. Twenty-six conversational pairs aged 10-19 years participated: 13 pairs consisting of a child/adolescent with CI (CI) and a conversational partner (CIP); and 13 pairs consisting of a normally hearing control (NH) and a conversational partner (NHP). The pairs performed a referential communication task requiring the description of faces. All occurrences of requests for clarification and their responses in the dialogues were identified and categorized. We also analysed how the different types of requests and responses were combined and the type-conformity of the responses to requests for confirmation. The results showed no significant group differences regarding type, distribution or type-conformity of responses. In all four groups (CI, CIP, NH and NHP), a discrepancy between the request and the response was found, indicating that the response provided information that was not explicitly requested. Requests for confirmation constituted 78-90% of the requests, whereas only 54-61% of responses were confirmations. Conversely, the proportion of requests for elaboration was 6-15%, whereas the proportion of elaborated responses was 34-40%. The children/adolescents with CI contribute equally to the conversation regarding type and distribution of responses to requests for clarification. The frequent use of elaborated responses indicates common ground for the conversational partners and a shared understanding of the objective of the task. The context creates facilitative conditions, with positive interactional consequences. The results have implications for the design of intervention, where tasks such as this can be used to make children with CI more aware of the role of questioning strategies in interaction.

Expressive vocabulary of children with hearing loss in the first 2 years of life: impact of early intervention

The aim of this study was to determine the expressive vocabulary of children with hearing loss (HL) enrolled in early intervention (EI) ≤ 3 vs >3 months in the first 24 months and to compare with hearing controls. It was hypothesized that the number of words produced would be higher for children with HL enrolled in EI ≤ 3 vs >3 months. This is a prospective longitudinal matched cohort study. The children with HL produced fewer words than the children with hearing. In addition, children with HL enrolled in EI ≤ 3 months had a larger expressive vocabulary percentile score compared with children with HL enrolled >3 months. Children with mild HL enrolled in EI ≤ 3 months had the greatest growth in vocabulary between 12 to 16 and 18 to 24 months. Although multiple factors are associated with expressive vocabulary growth of children with HL, enrollment in EI ≤ 3 months has sustained beneficial effects on expressive vocabulary at 18 to 24 months.

ORIGINAL ARTICLE: The bone‐anchored hearing aid in the rehabilitation of single‐sided deafness: experience with 58 patients

Clin. Otolaryngol. 2010, 35, 284–290Objectives: To assess the efficacy of the bone‐anchored hearing aid (BAHA) in the rehabilitation of single‐sided deafness (SSD).Study design: Retrospective case–control series review.Setting: Tertiary referral unit.Patients: Fifty‐eight consecutive patients that had a bone‐anchored hearing aid for single‐sided deafness completed outcome questionnaires, building upon earlier audiological assessment of 19 patients. Single‐sided deafness controls (n = 49) were mainly acoustic neuroma patients. Main outcome measurements: speech discrimination testing in directional noise, speech and spatial qualities of hearing questionnaire and the Glasgow Benefit Inventory (GBI).Results: The mean follow‐up time was 28.4 months. Five (13%) of the bone‐anchored hearing aid patients were non‐users because of lack of benefit. The audiometric testing confirmed that when noise was on the bone‐anchored hearing aid side speech perception was reduced but benefited when noise was on the side of the hearing ear. There was no difference between the Speech and Spatial Qualities of Hearing Scores in bone‐anchored hearing aid users and controls. In particular there was no difference in the spatial subscores. In the bone‐anchored hearing aid users the median Glasgow Benefit Inventory score was 11. If the non‐users are included then 13 (22%) patients had no or detrimental (negative) Benefit scores. No or negative benefit scores were more frequent in those deaf for &lt;10 years. In open‐field questions, patients felt the bone‐anchored hearing aid was most useful in small groups or in ‘one‐to‐one’ conversation.Conclusions: Bone‐anchored hearing aid rehabilitation for single‐sided deafness is less successful than for other indications, reflected here by relatively low median Glasgow Benefit Inventory scores. There was also no significant difference between controls and bone‐anchored hearing aid users in the Speech and Spatial Qualities of Hearing Questionnaire. Patients with a longer duration of deafness report greater subjective benefit than those more recently deafened, perhaps due to differing expectations.

Prevalence of the mitochondrial A 1555G mutation in Moroccan patients with non-syndromic hearing loss

Mutations in mitochondrial DNA (mtDNA), especially the A1555G transition in the 12S rRNA gene, are one of the causes of both aminoglycoside-induced and non-syndromic sensorineural hearing loss. Objective The aim of this study was to determine the prevalence of the A1555G mitochondrial mutation in Moroccan patients. Methods We performed molecular characterization by PCR-RFLP and direct sequencing of one hundred and sixty four patients (84 unrelated familial and 80 sporadic cases) with a congenital sensorineural non-syndromic hearing loss and one hundred normal hearing controls for the occurrence of the A1555G mutation. Results Mutational analysis of the mtDNA showed the presence of the homoplasmic A1555G mutation in three families, leading to a frequency of 3.6% similar to that reported for European-populations. No A1555G mutation was detected in sporadic and controls cases. However, we detected in twenty normal hearing controls a novel polymorphism A1557C, which was not found in patient samples. We further evidenced the presence of the A1438G mitochondrial polymorphism in four patients with sensorineural hearing loss and in five controls. Conclusion Our results show that the occurrence of the A1555G mutation in hearing impaired patient's accounts for 3.6% in a Moroccan patients and those novel mtDNA polymorphisms might contribute to a novel sub-haplogroup specific of the Magrheb.

Risk factors for sensorineural hearing loss in NICU infants compared to normal hearing NICU controls

Objectives To evaluate independent etiologic factors associated with sensorineural hearing loss in infants who have been admitted to the neonatal intensive care unit compared to normal hearing controls. Method Between 2004 and 2009, 3366 infants were admitted to the neonatal intensive care unit of Sophia Children's Hospital, of which 3316 were screened with AABR. A total of 103 infants were referred for auditory brainstem response analysis after failure on neonatal hearing screening. We included all infants diagnosed with sensorineural hearing loss. Each patient was matched with two normal hearing controls from the neonatal intensive care unit of the same gender and postconceptional age. The following risk factors were studied: birth weight, dysmorphic features, APGAR scores (at 1, 5 and 10 min), respiratory distress (IRDS), CMV infection, sepsis, meningitis, cerebral bleeding, cerebral infarction, hyperbilirubinemia requiring phototherapy, peak total bilirubin level, furosemide, dexamethason, vancomycin, gentamycin and tobramycin administration. Results Fifty-eight infants were diagnosed with sensorineural hearing loss: 26 girls and 32 boys. The incidence of dysmorphic features ( P = 0.000), low APGAR score (1 min) ( P = 0.01), sepsis ( P = 0.003), meningitis ( P = 0.013), cerebral bleeding ( P = 0.016) and cerebral infarction ( P = 0.000) were significantly increased in infants with sensorineural hearing loss compared to normal hearing controls ( n = 116). Conclusion Dysmorphic features, low APGAR scores at 1 min, sepsis, meningitis, cerebral bleeding and cerebral infarction are associated with sensorineural hearing loss independent of neonatal intensive care unit admittance.

3D mapping of brain differences in native signing congenitally and prelingually deaf subjects.

In the prelingual and congenital deaf, functional reorganization is known to occur throughout brain regions normally associated with hearing. However, the anatomical correlates of these changes are not yet well understood. Here, we perform the first tensor-based morphometric analysis of voxel-wise volumetric differences in native signing prelingual and congenitally deaf subjects when compared with hearing controls. We obtained T1-weighted scans for 14 native signing prelingual and congenitally deaf subjects and 16 age- and gender-matched controls. We used linear and fluid registration to align each image to a common template. Using the voxel-wise determinant of the Jacobian of the fluid deformation, significant volume increases, of up to 20%, were found in frontal lobe white matter regions including Broca's area, and adjacent regions involved in motor control and language production. A similar analysis was performed on hand-traced corpora callosa. A strong trend for group differences was found in the area of the splenium considered to carry fibers connecting the temporal (and occipital) lobes. These anatomical differences may reflect experience-mediated developmental differences in myelination and cortical maturation associated with prolonged monomodal sensory deprivation.

Altered spatial distribution of visual attention in near and far space after early deafness

Early deafness results in a redistribution of more attentional resources to the visual periphery in near space, specifically under conditions of selective attention, probably to compensate for the loss of auditory alertness to potentially dangerous stimuli from outside the current attentional focus. It remains poorly understood, however, whether spatial distribution of attention in far space is altered by early deafness as well. In the present study, we investigated whether and how early deafness alters the distribution of visuospatial attention in far space, compared to hearing controls. We asked deaf individuals and hearing controls to perform a flanker task with either peripheral or central distractors, either in near or far space. Sizes of compatibility effect were used to assess the amount of attentional resources received by the peripheral and central distractors. In near space, peripheral distractors induced significantly larger compatibility effect in deaf individuals than in hearing controls while central distractors induced significantly larger compatibility effect in hearing controls than in deaf individuals. On the other hand in far space, although peripheral distractors induced equivalent sizes of compatibility effect in the deaf and hearing groups, central distractors caused significant compatibility effect only in deaf individuals, but not in hearing controls. Our results suggest that early deafness results in a redistribution of visuospatial attention not only in near space but also in far space, with enhanced peripheral attention in near space and enhanced central attention in far space.

Neural correlates of human somatosensory integration in tinnitus

Possible neural correlates of somatosensory modulation of tinnitus were assessed. Functional magnetic resonance imaging (fMRI) was used to investigate differences in neural activity between subjects that can modulate their tinnitus by jaw protrusion and normal hearing controls. We measured responses to bilateral sound and responses to jaw protrusion. Additionally we studied multimodal integration of somatosensory jaw protrusion and sound. The auditory system responded to both sound and jaw protrusion. Jaw responses were enhanced in the cochlear nucleus (CN) and the inferior colliculus (IC) in tinnitus patients. The responses of the auditory brain areas to jaw protrusion presumable account for the modulation of tinnitus as described by the patients. The somatosensory system responded to jaw protrusion and not to sound. These responses occurred both in subjects with tinnitus and controls. Unexpectedly, the cerebellum responded to sound in normal hearing subjects, but not in tinnitus patients. Together, these results provide a neurophysiological basis for the effect of jaw protrusion on tinnitus.

GJB2 Mutations in Mongolia: Complex Alleles, Low Frequency, and Reduced Fitness of the Deaf

We screened the GJB2 gene for mutations in 534 (108 multiplex and 426 simplex) probands with non-syndromic sensorineural deafness, who were ascertained through the only residential school for the deaf in Mongolia, and in 217 hearing controls. Twenty different alleles, including four novel changes, were identified. Biallelic GJB2 mutations were found in 4.5% of the deaf probands (8.3% in multiplex, 3.5% in simplex). The most common mutations were c.IVS1 + 1G > A (c.-3201G > A) and c.235delC with allele frequencies of 3.5% and 1.5%, respectively. The c.IVS1 + 1G > A mutation appears to have diverse origins based on associated multiple haplotypes. The p.V27I and p.E114G variants were frequently detected in both deaf probands and hearing controls. The p.E114G variant was always in cis with the p.V27I variant. Although in vitro experiments using Xenopus oocytes have suggested that p.[V27I;E114G] disturbs the gap junction function of Cx26, the equal distribution of this complex allele in both deaf probands and hearing controls makes it a less likely cause of profound congenital deafness. We found a lower frequency of assortative mating (37.5%) and decreased genetic fitness (62%) of the deaf in Mongolia as compared to the western populations, which provides an explanation for lower frequency of GJB2 deafness in Mongolia.

Neuroanatomic Differences in Children With Unilateral Sensorineural Hearing Loss Detected Using Functional Magnetic Resonance Imaging

Functional magnetic resonance imaging (fMRI) provides information about neuronal excitation by measuring changes in cerebral hemodynamics. This study used fMRI to compare neuroanatomic activation patterns in children with unilateral sensorineural hearing loss (USNHL) with the neuroanatomic activation patterns in normally hearing individuals. Patients were presented with narrowband noise and speech-in-noise tasks while undergoing fMRI of the brain. In the narrowband noise task, 5 chirps at center frequencies of 250 Hz, 500 Hz, 1 kHz, 2 kHz, and 4 kHz were presented monaurally for 1 second in a randomized order to children in both groups. In the speech-in-noise task, Bamford-Kowal-Bench (BKB) sentences were presented over 4-talker babble to both ears, and scans were acquired after each stimulus. We compared fMRI data across groups using independent component analysis and Bayesian (hierarchical) linear models. Tertiary referral center. Twelve children with USNHL and 23 normally hearing controls. Perform fMRI while subject listens to narrowband and speech-in-noise tasks. Neuroanatomic differences in fMRI. In the narrowband noise task, children with USNHL had less activation of auditory areas and failed to activate auditory association areas and attention networks compared with normally hearing controls. In the speech-in-noise task, children with USNHL activated only secondary auditory processing areas in the left hemisphere, while controls activated these areas bilaterally. Children with right-sided USNHL failed to activate attention areas that were activated in controls and in children with left-sided USNHL. Only children with left-sided USNHL activated bilateral visual association areas. Results show significant differences in the cortical processing of sound between children with severe to profound USNHL and normally hearing children. These differences may account for the functional auditory problems that children with USNHL experience.