The contribution of inferior colliculus activity to the auditory brainstem response (ABR) in mice.

In mice, the auditory brainstem response (ABR) is frequently used to assess hearing status in transgenic hearing models. The diagnostic value of the ABR depends on knowledge about the anatomical sources of its characteristic waves. Here, we studied the contribution of the inferior colliculus (IC) to the click-evoked scalp ABR in mice.

Higher-order auditory areas in congenital deafness: Top-down interactions and corticocortical decoupling.

The theory of predictive coding assumes that higher-order representations influence lower-order representations by generating predictions about sensory input. In congenital deafness, one identified dysfunction is a reduced activation of deep layers in the auditory cortex. Since these layers play a central role for processing top-down influences, congenital deafness might interfere with the integration of top-down and bottom-up information flow.

Differential Intracochlear Sound Pressure Measurements in Human Temporal Bones with an Off-the-Shelf Sensor.

The standard method to determine the output level of acoustic and mechanical stimulation to the inner ear is measurement of vibration response of the stapes in human cadaveric temporal bones (TBs) by laser Doppler vibrometry. However, this method is reliable only if the intact ossicular chain is stimulated. For other stimulation modes an alternative method is needed.

Female cats, but not males, adjust responsiveness to arousal in the voice of kittens.

Background: The infant cry is the most important communicative tool to elicit adaptive parental behaviour. Sex-specific adaptation, linked to parental investment, may have evolutionary shaped the responsiveness to changes in the voice of the infant cries. The emotional content of infant cries may trigger distinctive responsiveness either based on their general arousing properties, being part of a general affect encoding rule, or based on affective perception, linked to parental investment, differing between species.

Optoacoustic effect is responsible for laser-induced cochlear responses.

Optical stimulation of the cochlea with laser light has been suggested as an alternative to conventional treatment of sensorineural hearing loss with cochlear implants. The underlying mechanisms are controversially discussed: The stimulation can either be based on a direct excitation of neurons, or it is a result of an optoacoustic pressure wave acting on the basilar membrane. Animal studies comparing the intra-cochlear optical stimulation of hearing and deafened guinea pigs have indicated that the stimulation requires intact hair cells.

Cross-Modal Plasticity in Higher-Order Auditory Cortex of Congenitally Deaf Cats Does Not Limit Auditory Responsiveness to Cochlear Implants.

Unlabelled: Congenital sensory deprivation can lead to reorganization of the deprived cortical regions by another sensory system. Such cross-modal reorganization may either compete with or complement the "original" inputs to the deprived area after sensory restoration and can thus be either adverse or beneficial for sensory restoration. In congenital deafness, a previous inactivation study documented that supranormal visual behavior was mediated by higher-order auditory fields in congenitally deaf cats (CDCs).

The Effect of Simulated Mastoid Obliteration on the Mechanical Output of Electromagnetic Transducers.

Background: The electromagnetic transducers of implantable middle ear hearing devices or direct acoustic cochlear implants (DACIs) are intended for implantation in an air-filled middle ear cavity. When implanted in an obliterated radical mastoid cavity, they would be surrounded by fatty tissue of unknown elastic properties, potentially attenuating the mechanical output. Here, the elastic properties of this tissue were determined experimentally and the vibrational output of commonly used electromagnetic transducers in an obliterated radical mastoid cavity was investigated in vitro using a newly developed method.

Establishment of a long-term spiral ganglion neuron culture with reduced glial cell number: Effects of AraC on cell composition and neurons.

Background: Sensorineural deafness is mainly caused by damage to hair cells and degeneration of the spiral ganglion neurons (SGN). Cochlear implants can functionally replace lost hair cells and stimulate the SGN electrically. The benefit from cochlear implantation depends on the number and excitability of these neurons.

ATP-sensitive K(+) channels (Kir6.1/SUR1) regulate gap junctional coupling in cochlear-supporting cells.

Using the double whole-cell patch-clamp technique, we found that the absence of intracellular ATP led to gap junction uncoupling in cochlear-supporting Hensen cells. The uncoupling was observed as a progressive reduction of the gap junctional electrical conductance from a starting value of approximately 40 nS to less than 0.04 nS within 10-20 min.

Neurocognitive factors in sensory restoration of early deafness: a connectome model.

Progress in biomedical technology (cochlear, vestibular, and retinal implants) has led to remarkable success in neurosensory restoration, particularly in the auditory system. However, outcomes vary considerably, even after accounting for comorbidity-for example, after cochlear implantation, some deaf children develop spoken language skills approaching those of their hearing peers, whereas other children fail to do so. Here, we review evidence that auditory deprivation has widespread effects on brain development, affecting the capacity to process information beyond the auditory system.

Monaural Congenital Deafness Affects Aural Dominance and Degrades Binaural Processing.

Cortical development extensively depends on sensory experience. Effects of congenital monaural and binaural deafness on cortical aural dominance and representation of binaural cues were investigated in the present study. We used an animal model that precisely mimics the clinical scenario of unilateral cochlear implantation in an individual with single-sided congenital deafness.

A 3D-printed functioning anatomical human middle ear model.

The middle ear is a sophisticated and complex structure with a variety of functions, yet a delicate organ prone to injuries due to various reasons. Both, understanding and reconstructing its functions has always been an important topic for researchers from medical and technical background. Currently, human temporal bones are generally used as model for tests, experiments and validation of the numerical results.

Cochlear Implant Stimulation of a Hearing Ear Generates Separate Electrophonic and Electroneural Responses.

Unlabelled: Electroacoustic stimulation in subjects with residual hearing is becoming more widely used in clinical practice. However, little is known about the properties of electrically induced responses in the hearing cochlea. In the present study, normal-hearing guinea pig cochleae underwent cochlear implantation through a cochleostomy without significant loss of hearing.

Outer ear canal sound pressure and bone vibration measurement in SSD and CHL patients using a transcutaneous bone conduction instrument.

The intraoperative and postoperative objective functional assessment of transcutaneous bone conduction implants is still a challenge. Here we compared intraoperative Laser-Doppler-vibrometry (LDV, Polytec Inc.) to measure vibration of the bone close to the implant to Outer Ear Canal Sound Pressure Level (OEC-SPL) measurements.

Somatic memory and gain increase as preconditions for tinnitus: Insights from congenital deafness.

Tinnitus is the conscious perception of sound heard in the absence of physical sound sources internal or external to the body. The characterization of tinnitus by its spectrum reflects the missing frequencies originally represented in the hearing loss, i.e.

Detection of antibodies against Theiler's murine encephalomyelitis virus GDVII strain in experimental guinea pigs.

A disease affecting guinea pigs called 'guinea pig lameness' characterized by clinical signs of depression, lameness of limbs, flaccid paralysis, weight loss and death within a few weeks was first described by Römer in 1911. After a research group in our facility kept laboratory guinea pigs from two different origins together in one room, lameness was observed in two animals. Further investigations revealed a serological immune response against Theiler's murine encephalomyelitis virus (TMEV; GDVII strain) in these animals.

Electro-Mechanical Stimulation of the Cochlea by Vibrating Cochlear Implant Electrodes.

Introduction: Electro-acoustic stimulation (EAS) of the cochlea uses the preserved residual low-frequency hearing for acoustic stimulation in combination with electrical stimulation. The acoustic low-frequency component is amplified and high-frequency hearing is enhanced by a cochlear implant (CI). In this work, the feasibility of EAS by the floating mass transducers (FMTs) firmly attached to the implanted electrode was investigated and the achieved stapes displacement was compared with sound stimulation.

Neuronal Survival, Morphology and Outgrowth of Spiral Ganglion Neurons Using a Defined Growth Factor Combination.

Objectives: The functionality of cochlear implants (CI) depends, among others, on the number and excitability of surviving spiral ganglion neurons (SGN). The spatial separation between the SGN, located in the bony axis of the inner ear, and the CI, which is inserted in the scala tympani, results in suboptimal performance of CI patients and may be decreased by attracting the SGN neurites towards the electrode contacts. Neurotrophic factors (NTFs) can support neuronal survival and neurite outgrowth.

Asymmetric Hearing During Development: The Aural Preference Syndrome and Treatment Options.

Deafness affects ∼2 in 1000 children and is one of the most common congenital impairments. Permanent hearing loss can be treated by fitting hearing aids. More severe to profound deafness is an indication for cochlear implantation.

Strengthening of hearing ear representation reduces binaural sensitivity in early single-sided deafness.

Single-sided deafness initiates extensive adaptations in the central auditory system, with the consequence that a stronger and a weaker ear representation develops in the auditory brain. Animal studies demonstrated that the effects are substantially stronger if the condition starts early in development. Sequential binaural cochlear implantations with longer interimplant delays demonstrate that the speech comprehension at the weaker ear is substantially compromised.

The Codacs™ direct acoustic cochlear implant actuator: exploring alternative stimulation sites and their stimulation efficiency.

This work assesses the efficiency of the Codacs system actuator (Cochlear Ltd., Sydney Australia) in different inner ear stimulation modalities. Originally the actuator was intended for direct perilymph stimulation after stapedotomy using a piston prosthesis.

Auditory feedback modulates development of kitten vocalizations.

Effects of hearing loss on vocal behavior are species-specific. To study the impact of auditory feedback on feline vocal behavior, vocalizations of normal-hearing, hearing-impaired (white) and congenitally deaf (white) cats were analyzed at around weaning age. Eleven animals were placed in a soundproof booth for 30 min at different ages, from the first to the beginning of the fourth postnatal month, every 2 weeks of life.

Electric-acoustic interactions in the hearing cochlea: single fiber recordings.

The present study investigates interactions of simultaneous electric and acoustic stimulation in single auditory nerve fibers in normal hearing cats. First, the auditory nerve was accessed with a microelectrode and response areas of single nerve fibers were determined for acoustic stimulation. Second, response thresholds to extracochlear sinusoidal electric stimulation using ball electrodes positioned at the round window were measured.

In vitro and in vivo evaluation of a hydrogel reservoir as a continuous drug delivery system for inner ear treatment.

Fibrous tissue growth and loss of residual hearing after cochlear implantation can be reduced by application of the glucocorticoid dexamethasone-21-phosphate-disodium-salt (DEX). To date, sustained delivery of this agent to the cochlea using a number of pharmaceutical technologies has not been entirely successful. In this study we examine a novel way of continuous local drug application into the inner ear using a refillable hydrogel functionalized silicone reservoir.

Variations in microanatomy of the human cochlea.

The human cochlea shows considerable interindividual variability in size and morphology. In order to develop atraumatic cochlear implant (CI) electrodes, high-precision details of the variability of human anatomy are required. Sixteen human temporal bones were cut around the cochlea in blocks of approximately 3.