Association of the FBXO11 gene with chronic otitis media with effusion and recurrent otitis media: the Minnesota COME/ROM Family Study

OBJECTIVE: The FBXO11 gene is the human homologue of the gene mutated in the novel deaf mouse mutant jeff (Jf), a single gene model of otitis media. We have evaluated single nucleotide polymorphisms (SNPs) in the FBXO11 gene for association with chronic otitis media with effusion/recurrent otitis media (COME/ROM). DESIGN: A total of 13 SNPs were genotyped across the 98.7 kilobases of genomic DNA encompassing FBXO11. Data were analyzed for single SNP association using generalized estimating equations, and haplotypes were evaluated using Pedigree Disequilibrium Test methods. PATIENTS: The Minnesota COME/ROM Family Study, a group of 142 families (619 subjects) with multiple affected individuals with COME/ROM. MAIN OUTCOME MEASURES: Genetic association of COME/ROM with polymorphisms in FBXO11. RESULTS: The FBXO11 SNPs are contained in a single linkage disequilibrium haplotype block. Ten of the 13 SNPs were sufficiently polymorphic in the sample to permit analysis. In univariate genetic analysis, 1 reference SNP (hereinafter rs) (rs2134056) showed nominal evidence of association to COME/ROM (P = .02), and 2 SNPs approached significance (rs2020911, P = .06; rs3136367, P = .09). In multivariable analyses, including known risk factors for COME/ROM (sex, exposure to smoking, attending day care centers, no prior breastfeeding, and having allergies), the evidence of independent association was reduced for each SNP (eg, rs2134056, from P = .02 to P = .08). In subsequent analyses using the Pedigree Disequilibrium Test, the association of FBXO11 SNP rs2134056 (P = .06) with COME/ROM was confirmed. Incorporating multiple SNPs in 2- and 3-locus SNP haplotypes, those haplotypes containing rs2134056 also exhibited evidence of association of FBXO11 and COME/ROM (P values ranging from .03 to .10). CONCLUSION: We have observed evidence consistent with an association between polymorphisms in FBXO11, the human homologue of the Jeff mouse model gene, and COME/ROM.     

Enhanced Vestibulo-ocular Reflex to Electrical Vestibular Stimulation in Meniere’s Disease

Meniere’s disease is characterized by sporadic episodes of vertigo, nystagmus, fluctuating sensorineural hearing loss, tinnitus and aural pressure. Since Meniere’s disease can affect different regions of the vestibular labyrinth, we investigated if electrical vestibular stimulation (EVS) which excites the entire vestibular labyrinth may be useful to reveal patchy endorgan pathology. We recorded three-dimensional electrically evoked vestibulo-ocular reflex (eVOR) to transient EVS using bilateral, bipolar 100-ms current steps at intensities of 0.9, 2.5, 5.0, 7.5 and 10.0 mA with dual-search coils in 12 unilateral Meniere’s patients. Their results were compared to 17 normal subjects. Normal eVOR had tonic and phasic spatiotemporal properties best described by the torsional component, which was four times larger than horizontal and vertical components. At EVS onset and offset of 8.9 ms latency, there were phasic eVOR initiation (M = 1,267 °/s²) and cessation (M = −1,675 °/s²) acceleration pulses, whereas during the constant portion of the EVS, there was a maintained tonic eVOR (M = 9.1 °/s) at 10 mA. However in Meniere’s disease, whilst latency of EVS onset and offset was normal at 9.0 ms, phasic eVOR initiation (M = 1,720 °/s²) and cessation (M = −2,523 °/s²) were enlarged at 10 mA. The initiation profile was a bimodal response, whilst the cessation profile frequently did not return to baseline. The tonic eVOR (M = 20.5 °/s) exhibited a ramped enhancement of about twice normal at 10 mA. Tonic eVOR enhancement was present for EVS >0.9 mA and disproportionately enhanced the torsional, vertical and horizontal components. These eVOR abnormalities may be a diagnostic indicator of Meniere’s disease and may explain the vertigo attacks in the presence of declining mechanically evoked vestibular responses.     

Chemical composition of Galla chinensis extract and the effect of its main component(s) on the prevention of enamel demineralization in vitro

To determine the chemical composition of Galla chinensis extract(GCE) by several analysis techniques and to compare the efficacy of GCE and its main component(s) in inhibition of enamel demineralization,for the development of future anticaries agents,main organic composition of GCE was qualitatively determined by liquid chromatography-time of flight-mass spectrometry(LC-TOF-MS) and quantified by high-performance liquid chromatography-diode array detector(HPLC-DAD).Inorganic ions were tested by inductively coupled plasma-atomic emission spectroscopy and F was especially measured by ion chromatography.Then,bovine enamel blocks were randomly divided into four treatment groups and were subjected to a pH-cycling regime for 12 times.Each cycle included 5-min applications with one of four treatments:4 g?L 21 GCE solution,4 g?L 21 gallic acid(GA) solution,1 g?L 21 NaF solution(positive control),deionized water(DDW,negative control),and then 60-min application in pH 5.0 acidic buffer and 5-min application in neutral buffer.Acidic buffers were retained for calcium analysis.The main organic composition of GCE were GA and its isomer,and,to a lesser extent,small molecule gallotannins.The content of GA in GCE was 71.3%60.2%(w/w).Inorganic ions were present in various amounts,of which Ca was(13662.82) mg?g 21,and Zn was(6.860.1) mg?g 21.No F was detected in GCE.In pH cycling,GA showed an effect similar to GCE in inhibiting enamel demineralization(P.0.05).GA was found to be the main effective,demineralization inhibiting component of GCE and could be a promising agent for the development of anticaries agents.     

Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients

This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients （TECs）, when zirconia ceramics were coloured at green stage. Zirconia blocks （N=240; 6 mm x 7 mm x 7 mm） were manufactured from two materials namely, ICE Zirconia （Group 1） and Prettau Zirconia （Group 2）. In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid （shade A2）, Three different veneering ceramics with different TEC （ICE Ceramic, GC Initial Zr and IPS e.max Ceram） were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys （Esteticor Plus） veneered with ceramic （VM 13） （n= 16） acted as the control group. Core-veneer interface of the specimens were subjected to shear force in the Universal Testing Machine （0.5 mm-min-1）. Neither the zirconia core material （P=0.318） nor colouring （P=0.188） significantly affected the results （three-way analysis of variance, Tukey＇s test）. But the results were significantly affected by the veneering ceramic （P=0.000）. Control group exhibited significantly higher mean bond strength values （45.7__.8） MPa than all other tested groups （（27.1__.4.1）-（39.7__.4.7） and （27.4__.5.6）-（35.9___4.7） MPa with and without colouring, respectively） （P~0.001）. While in zirconia-veneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering ~ 1/3 of the substrate surface, in the metal-ceramic group, veneering ceramic was left adhered 1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core-veneer adhesion. Metal-ceramic adhesion was more reliable than all zirconia-veneer ceramics tested.     

Evaluation of the Interleukin-1 Receptor Antagonist and Immunoregulatory Interleukin-10 in the Middle Ear in Chronic Otitis Media With Effusion in Children With and Without Atopy

ObjectivesThe role of pro-inflammatory cytokines in the course of chronic otitis media with effusion (COME) has been documented. However, there are fewer studies on the action of anti-inflammatory cytokines in the middle ear. We sought determine whether there is an association between COME and anti-inflammatory cytokines and whether there are any differences in the cytokine profile in COME children with and without atopy.MethodsEighty-four children were divided into 3 groups: 32 nonatopic children with COME (group NA), 31 atopic children with COME (group A), and 21 children without COME and without atopy (control group C). Specimens from the middle ear were collected and evaluated by enzyme-linked immunosorbent assay for the cytokines interleukin-1 receptor antagonist (IL-1Ra) and immunoregulatory IL-10.ResultsSignificantly higher IL-10 concentrations were found in both nonatopic and atopic children with COME compared to controls. No significant differences in IL-1Ra levels were found between atopic and nonatopic children with COME and the control group.ConclusionWe found no differences in the levels of IL-1Ra in atopic and nonatopic children with COME compared to controls. However, we found elevated IL-10 levels in the middle ear effusions from children with COME, with or without atopy. These elevated immunoregulatory cytokine levels suggest a role for new immunomodulatory treatments to prevent disease progression in COME, regardless of atopy.     

Influence of acrylamide monomer addition to the acrylic denture-base resins on mechanical and physical properties

The aim of the study was to evaluate the effect of adding acrylamide monomer （AAm） on the characterization, flexural strength, flexural modulus and thermal degradation temperature of poly（methyl methacrylate） （PMMA） denture-base resins. Specimens （n= 10） were fabricated from a conventional heat-activated QC-20 （Qc-） and a microwave heat-activated Acron MC （Ac-） PMMA resins. Powder/ liquid ratio followed the manufacturer＇s instructions for the control groups （Qc-c and Ac-c） and for the copolymer groups, the resins were prepared with 5% （-5）, 10% （- 10）, 15% （- 15） and 20% （-20） acrylamide contents, according to the molecular weight ratio, respectively. The flexural strength and flexural modulus were measured by a three-point bending test. The data obtained were statistically analyzed by Kruskal-Wallis test （a=O.05） to determine significant differences between the groups, The chemical structures of the resins were characterized by the nuclear magnetic resonance spectroscopy. Thermal stabilities were determined by thermogravimetric analysis （TGA） with a heating rate of 10 ~C.min-1 from 35 ~C to 600 ~C. Control groups from both acrylic resins showed the lowest flexural strength values. Qc-15 showed significant increase in the flexural strength when compared to Qc-c （P〈O.01）. Ac-10 and Ac-15 showed significance when compared to Ac-c （P〈O.01）. Acrylamide incorporation increased the elastic modulus in Qc-10, Qc-15 and Qc-20 when compared to Qc-c （P〈0.01）. Also significant increase was observed in Ac-10, Ac-15 and Ac-20 copolymer groups when compared to Ac-c （P〈0.01）. According to the 1H-nuclear magnetic resonance （NMR） results, acrylamide copolymerization was confirmed in the experimental groups. TGA results showed that the thermal stability of PMMA is increased by the insertion of AAm.     

Association of the oncostatin m receptor gene polymorphisms with papillary thyroid cancer in the korean population

Objectives

To investigate the association between papillary thyroid cancer (PTC) and single nucleotide polymorphisms (SNPs) of oncostatin M receptor (OSMR) in the Korean population.

Methods

Retrospective case-control study was done. Eighty-five patients with PTC and 287 controls were studied. One missense SNP (rs2278329, Asp553Asn) and one promoter SNP (rs2292016, -100 G/T) of the OSMR gene were genotyped by direct sequencing. Genetic data were analyzed using the SNPStats, Helixtree, and SNPAnalyzer Pro. PTC patients were dichotomized and compared with respect to the clinicopathologic characteristics.

Results

There was no association between genotypes and allele frequencies of OSMR SNPs (rs2278329 and rs2292016) and PTC susceptibility. SNP rs2278329 was significantly associated with tumor size (dominant model; P=0.028; odds ratio [OR], 2.71; 95% confidence interval [CI], 1.12 to 6.57). The A allele was higher in sizes large than 1 cm (32.5% vs. 16.7%; P=0.018; OR, 2.41; 95% CI, 1.17 to 4.98). Regarding the number of tumors, we found no significant association with genotype, however, the A allele was higher in patients with multifocaltiy (33.3% vs. 19.1%; P=0.040; OR, 2.12; 95% CI, 1.03 to 4.34).

Conclusion

The results suggest that OSMR polymorphism rs2278329 is associated with clinicopathologic characteristics of the tumor growth and multifocality development.     

Sensory innervation around immediately vs. delayed loaded implants:a pilot study

Although neurophysiological and psychophysical proof of osseoperception is accumulating, histomorphometric evidence for the neural mechanisms of functional compensation following immediate and delayed ...     

Hyperpolarization-Activated Current (I h) in Vestibular Calyx Terminals: Characterization and Role in Shaping Postsynaptic Events

Calyx afferent terminals engulf the basolateral region of type I vestibular hair cells, and synaptic transmission across the vestibular type I hair cell/calyx is not well understood. Calyces express several ionic conductances, which may shape postsynaptic potentials. These include previously described tetrodotoxin-sensitive inward Na⁺ currents, voltage-dependent outward K⁺ currents and a K(Ca) current. Here, we characterize an inwardly rectifying conductance in gerbil semicircular canal calyx terminals (postnatal days 3–45), sensitive to voltage and to cyclic nucleotides. Using whole-cell patch clamp, we recorded from isolated calyx terminals still attached to their type I hair cells. A slowly activating, noninactivating current (I_h) was seen with hyperpolarizing voltage steps negative to the resting potential. External Cs⁺ (1–5 mM) and ZD7288 (100 μM) blocked the inward current by 97 and 83 %, respectively, confirming that I_h was carried by hyperpolarization-activated, cyclic nucleotide gated channels. Mean half-activation voltage of I_h was −123 mV, which shifted to −114 mV in the presence of cAMP. Activation of I_h was well described with a third order exponential fit to the current (mean time constant of activation, τ, was 190 ms at −139 mV). Activation speeded up significantly (τ = 136 and 127 ms, respectively) when intracellular cAMP and cGMP were present, suggesting that in vivo I_h could be subject to efferent modulation via cyclic nucleotide-dependent mechanisms. In current clamp, hyperpolarizing current steps produced a time-dependent depolarizing sag followed by either a rebound afterdepolarization or an action potential. Spontaneous excitatory postsynaptic potentials (EPSPs) became larger and wider when I_h was blocked with ZD7288. In a three-dimensional mathematical model of the calyx terminal based on Hodgkin–Huxley type ionic conductances, removal of I_h similarly increased the EPSP, whereas cAMP slightly decreased simulated EPSP size and width.     

Growth inhibitory response and ultrastructural modification of oral-associated candidal reference strains （ATCC） by Piper betle L. extract

Candida species have been associated with the emergence of strains resistant to selected antifungal agents. Plant products have been used traditionally as alternative medicine to ease mucosal fungal infections. This study aimed to investigate the effects of Piper betle extract on the growth profile and the ultrastructure of commonly isolated oral candidal cells. The major component of Po betle was identified using liquid chromatography-mass spectrophotometry （LC-MS/MS）. Seven ATCC control strains of Candida species were cultured in yeast peptone dextrose broth under four different growth environments： （i） in the absence of P. betle extract; and in the presence of P. beUeextract at respective concentrations of （ii） 1 mg.mL-1; （iii） 3 mg.mL-1; and （iv） 6 mg.mL- 1 The growth inhibitory responses of the candidal cells were determined based on changes in the specific growth rates （μ）. Scanning electron microscopy （SEM） was used to observe any ultrastructural alterations in the candida colonies. LC-MS/MS was performed to validate the presence of bioactive compounds in the extract. Following treatment, it was observed that the p-values of the treated cells were significantly different than those of the untreated cells （P〈0.05）, indicating the fungistatic properties of the P. beUe extract. The candidal population was also reduced from an average of 13.44× 10^6 to 1.78×10^6 viable cell counts （CFU）.mL-1, SEM examination exhibited physical damage and considerable morphological alterations of the treated cells. The compound profile from LC-MS/MS indicated the presence of hydroxybenzoic acid, chavibetol and hydroxychavicol in P. betle extract. The effects of P. betle on candida cells could potentiate its antifungal activity.     

Effect of Nebulized Bovine Surfactant for Experimental Otitis Media with Effusion

Objectives

In this study, we evaluated the efficacy of nebulized bovine pulmonary surfactant on experimentally induced otitis media with effusion (OME) in guinea pigs.

Methods

Twenty guinea pigs were divided into three groups. Four untreated animals served as normal controls. Experimental OME was established in both ears of the remaining 16 animals by a transbullar injection of 10 µL of Pseudomonas aeruginosa lipopolysaccharide in saline. Thereafter, the guinea pigs received nebulized phosphate buffered saline (n=8) or nebulized bovine pulmonary surfactant (n=8). Nebulization was given daily for 7 days. On day 8, all the animals'' passive opening pressure (POP) of the Eustachian tube was measured and histopathological observations of the bulla were made by light microscopy.

Results

Nebulized bovine pulmonary surfactant significantly reduced the POP compared to that of saline nebulization. The bovine pulmonary surfactant improved the tubal patency and produced less histopathologcally-evident edematous bullar mucosa.

Conclusion

Nebulization of bovine pulmonary surfactant plays an important role in treating otitis media with effusion in guinea pigs. Our results suggest that the chosen nebulized bovine pulmonary surfactant can be of good clinical benefit for treating OME in the future.     

Microbiology of the middle ear fluid in Costa Rican children between 2002 and 2007

Background

Because the microbiology and susceptibility patterns of middle ear fluid pathogens in children with otitis media change over time, an active surveillance is recommended to establish appropriate therapeutic guidelines.

Objective

To analyze the microbiology and susceptibility pattern of middle ear pathogens obtained from Costa Rican children with acute otitis media (AOM), recurrent otitis media (ROM) and therapeutic failure otitis media (OMTF) between 2002 and 2007.

Patients and methods

1108 children aged 2-92 months who participated in various otitis media clinical trials between the years 2002 and 2007.

Results

Among the study population, 880 were children with AOM (61% <24 months of age), 138 were children with ROM (54% <24 months of age) and 90 were children with OMTF (67% <24 months of age). Bilateral otitis media was more frequent in children with OMTF (44%) than in children with AOM (37%) (P = 0.19) and ROM (27%) (P = 0.009). Presence of siblings <8 years of age was more frequently observed in children with OMTF (73%) than in children with ROM (65%) (P = 0.0001) and AOM (47%) (P = 0.000002). Overall Streptococcus pneumoniae (44%) was the most common pathogen isolated followed by Haemophilus influenzae (37%), Moraxella catarrhalis (11%) and Streptococcus pyogenes (4%). S. pneumoniae was the most common pathogen in AOM (44%) and ROM (47%), however, H. influenzae was the most common pathogen in OMTF (40%). Among all H. influenzae, an increase in the number of β-lactamase producing strains was observed from 5.2% in 2001 to 14% (P = 0.04) in 2007 and this was associated with an increase in the use of amoxicillin. An increase in the number of M. catarrhalis was also observed, from 3% (9/350) in 2001 to 11% (71/628) (P = 0.000003) in 2007. During the study period the incidence of penicillin non-susceptible S. pneumoniae was 42/211 (20%) in children with AOM; 5/35 (17%) in children with ROM and 5/17 (42%) in children with OMTF. M. catarrhalis cases increased from 8% in 2004 to 17% in 2007 (P = 0.0005) and S. pyogenes decreased from 7% in 2002-2004 to 1% in 2005-2007 (P = 0.001).

Conclusions

In Costa Rica, S. pneumoniae remains the most common pathogen in children with AOM and ROM whereas non-typable H. influenzae remains the most common pathogen in children with OMTF. A significant increase in the number of β-lactamase positive H. influenzae and M. catarrhalis has been observed in recent years.     

Endoscopic Adenoidectomy in Children With Otitis Media With Effusion and Mild Hearing Loss

ObjectivesSurgical management of children with chronic otitis media with effusion (OME) includes tympanostomy tube insertion or adenoidectomy, alone or with myringotomy and tube insertion. The aim of this study was to compare the effectiveness of transoral microdebrider endoscopic-assisted adenoidectomy (TOMEA) and traditional adenoidectomy in the management of children with mild hearing loss due to OME and chronic adenoiditis.MethodsThis prospective, double-blind and controlled study involved 120 consecutive patients aged 4–12 years, who were randomised 1:1 to undergo TOMEA or traditional adenoidectomy under general anesthesia. All the patients underwent a complete otolaryngological examination, including nasopharyngeal fibre endoscopy (NFE), pneumatic otoscopy, otomicroscopy, tympanometry and supraliminar tonal audiometry, upon enrolment, and three and nine months postoperatively.ResultsThere were no statistically significant differences in age or gender distribution between the TOMEA group (mean age, 4.9±1.1 years; 53.3% males) and the traditional adenoidectomy group (mean age, 5.3±0.9 years; 56.7% males). Both procedures led to a significant improvement in choanal patency (P<0.01) and all of the otological and audiological parameters (P<0.01) 3 and 9 months postoperatively, although postoperative NFE showed that the mean percentage of residual choanal obstruction was significantly less in the TOMEA group (P=0.02). There was no significant between-group difference in the percentage of children with tympanic membrane changes, but the postoperative prevalence of children with a type B tympanogram was significantly lower in the TOMEA group after 3 (15.0% vs. 31.7%, P=0.05) and 9 months (18.3% vs. 38.3%, P=0.02), as was the percentage of children with mild conductive hearing loss (3.3% vs. 23.3%, P<0.01; and 8.3% vs. 28.3%, P<0.01).ConclusionAlthough both TOMEA and traditional adenoidectomy are effective in treating children with mild hearing loss due to adenoidal hypertrophy and OME, the former achieves the greater reduction in residual adenoidal hypertrophy and better audiological outcomes.     

Effect of Galla chinensis on the remineralization of two bovine root lesions morphous in vitro

The present study aims to evaluate the effect of Galla chinensis compounds on the remineralization of two artificial root lesions morphous in vitro.Sixty bovine dentine blocks were divided into two groups and individually treated with two levels of demineralization solutions to form erosive and subsurface artificial carious lesions in vitro.Each group was then divided into three subgroups,each of which were treated with a remineralization solution(positive control),deionized water(negative control),or 4 000 mg?L 21 aqueous solutions of Galla chinensis extract.The dentine blocks were then subjected to a pH-cycling regime for 7 days.During the first 4 days,the daily cycle included 21-h deal and 3-h demineralization applications.The dentine blocks were dealt with the entire day during the remaining 3 days.Two specimens from each of the treatment groups were selected and observed under a polarized light microscope.Data collected using a laser scanning confocal microscope were computerized and analyzed.Galla chinensis extract clearly enhanced the remineralization of both erosive lesion and subsurface lesion patterns in the specimens(P,0.05).The level of remineralization of the erosive lesion by Galla chinensis extract was lower than that of the subsurface lesion(P,0.05).In addition,the remineralization of the subsurface lesion by Galla chinensis extract was higher than that of the remineralization solution(P,0.05).No significant difference between the remineralization of erosive lesions by Galla chinensis extract and the remineralization solution was observed(P.0.05).So Galla chinensis extract has the potential to improve the remineralization of artificial root lesions under dynamic pH-cyclic conditions,indicating its potential use as a natural remineralization medicine.     

Unilateral Adaptation of the Human Angular Vestibulo-Ocular Reflex

A recent study showed that the angular vestibulo-ocular reflex (VOR) can be better adaptively increased using an incremental retinal image velocity error signal compared with a conventional constant large velocity-gain demand (×2). This finding has important implications for vestibular rehabilitation that seeks to improve the VOR response after injury. However, a large portion of vestibular patients have unilateral vestibular hypofunction, and training that raises their VOR response during rotations to both the ipsilesional and contralesional side is not usually ideal. We sought to determine if the vestibular response to one side could selectively be increased without affecting the contralateral response. We tested nine subjects with normal vestibular function. Using the scleral search coil and head impulse techniques, we measured the active and passive VOR gain (eye velocity / head velocity) before and after unilateral incremental VOR adaptation training, consisting of self-generated (active) head impulses, which lasted ∼15 min. The head impulses consisted of rapid, horizontal head rotations with peak-amplitude 15 ^o, peak-velocity 150 ^o/s and peak-acceleration 3,000 ^o/s². The VOR gain towards the adapting side increased after training from 0.92 ± 0.18 to 1.11 ± 0.22 (+22.7 ± 20.2 %) during active head impulses and from 0.91 ± 0.15 to 1.01 ± 0.17 (+11.3 ± 7.5 %) during passive head impulses. During active impulses, the VOR gain towards the non-adapting side also increased by ∼8 %, though this increase was ∼70 % less than to the adapting side. A similar increase did not occur during passive impulses. This study shows that unilateral vestibular adaptation is possible in humans with a normal VOR; unilateral incremental VOR adaptation may have a role in vestibular rehabilitation. The increase in passive VOR gain after active head impulse adaptation suggests that the training effect is robust.     

Current Steering with Partial Tripolar Stimulation Mode in Cochlear Implants

The large spread of excitation is a major cause of poor spectral resolution for cochlear implant (CI) users. Partial tripolar (pTP) mode has been proposed to reduce current spread by returning an equally distributed fraction (0.5 × σ) of current to two flanking electrodes and the rest to an extra-cochlear ground. This study tested the efficacy of incorporating current steering into pTP mode to add spectral channels. Different proportions of current [α × σ and (1 − α) × σ] were returned to the basal and apical flanking electrodes respectively to shape the electric field. Loudness and pitch perception with α from 0 to 1 in steps of 0.1 was simulated with a computational model of CI stimulation and tested on the apical, middle, and basal electrodes of six CI subjects. The highest σ allowing for full loudness growth within the implant compliance limit was chosen for each main electrode. Pitch ranking was measured between pairs of loudness-balanced steered pTP stimuli with an α interval of 0.1 at the most comfortable level. Results demonstrated that steered pTP stimuli with α around 0.5 required more current to achieve equal loudness than those with α around 0 or 1, maybe due to more focused excitation patterns. Subjects usually perceived decreasing pitches as α increased from 0 to 1, somewhat consistent with the apical shift of the center of gravity of excitation pattern in the model. Pitch discrimination was not better with α around 0.5 than with α around 0 or 1, except for some subjects and electrodes. For three subjects with better pitch discrimination, about half of the pitch ranges of two adjacent main electrodes overlapped with each other in steered pTP mode. These results suggest that current steering with focused pTP mode may improve spectral resolution and pitch perception with CIs.     

Rapid Increase in Neural Conduction Time in the Adult Human Auditory Brainstem Following Sudden Unilateral Deafness

Individuals with sudden unilateral deafness offer a unique opportunity to study plasticity of the binaural auditory system in adult humans. Stimulation of the intact ear results in increased activity in the auditory cortex. However, there are no reports of changes at sub-cortical levels in humans. Therefore, the aim of the present study was to investigate changes in sub-cortical activity immediately before and after the onset of surgically induced unilateral deafness in adult humans. Click-evoked auditory brainstem responses (ABRs) to stimulation of the healthy ear were recorded from ten adults during the course of translabyrinthine surgery for the removal of a unilateral acoustic neuroma. This surgical technique always results in abrupt deafferentation of the affected ear. The results revealed a rapid (within minutes) reduction in latency of wave V (mean pre = 6.55 ms; mean post = 6.15 ms; p < 0.001). A latency reduction was also observed for wave III (mean pre = 4.40 ms; mean post = 4.13 ms; p < 0.001). These reductions in response latency are consistent with functional changes including disinhibition or/and more rapid intra-cellular signalling affecting binaurally sensitive neurons in the central auditory system. The results are highly relevant for improved understanding of putative physiological mechanisms underlying perceptual disorders such as tinnitus and hyperacusis.     

Experimental Measurement of Utricle System Dynamic Response to Inertial Stimulus

The membranous utricle sac of the red-eared turtle was mounted in a piezoelectric actuated platform mounted on the stage of a light microscope. The piezoelectric actuator oscillated the base of the neuroepithelium along a linear axis. Displacements were in the plane of the utricle and consisted of a linear sinusoidal-sweep signal starting at 0 and increasing to 500 Hz over 5 s. This inertial stimulus caused measurable shear displacement of the otoconial layer’s dorsal surface, resulting in shear deformation of the gelatinous and column filament layers. Displacements of the otoconial layer and a reference point on the neuroepithelium were filmed at 2,000 frames/s with a high-speed video camera during oscillations. Image registration was performed on the video to track displacements with a resolution better than 15 nm. The displacement waveforms were then matched to a linear second-order model of the dynamic system. The model match identified two system mechanical parameters—the natural circular frequency ω_n and the damping ratio ζ—that characterized the utricle dynamic response. The median values found for the medial-lateral axis on 20 utricles with 95 % confidence intervals in parenthesis were as follows: ω_n = 374 (353, 396) Hz and ζ = 0.50 (0.47, 0.53). The anterior-posterior axis values were not significantly different: ω_n = 409 (390, 430) Hz and ζ = 0.53 (0.48, 0.57). The results have two relevant and significant dynamic system findings: (1) a higher than expected natural frequency and (2) significant under damping. Previous to this study, utricular systems were treated as overdamped and with natural frequencies much lower that measured here. Both of these system performance findings result in excellent utricle time response to acceleration stimuli and a broad frequency bandwidth up to 100 Hz. This study is the first to establish the upper end of this mechanical system frequency response of the utricle in any animal.