Intrinsic Hearing Protection Mechanisms: A Pathway To Prevention Of Noise-induced Hearing Loss
Funder
National Health and Medical Research Council
Funding Amount
$625,900.00
Summary
Noise-induced hearing loss (NIHL) is a significant contributor to the total burden of disease. We recently determined that when the ear is exposed to sustained noise, the cochlea is protected from damage by activation of a specific (P2X2) receptor, evident as reversible hearing adaptation. This study will determine the downstream signalling from this receptor. This will support assessment of vulnerability to NIHL and contribute to development of hearing therapeutics.
Cochlear Type II Neurons In Contralateral Suppression
Funder
National Health and Medical Research Council
Funding Amount
$459,434.00
Summary
Sound in one ear affects hearing in the other ear. This contralateral suppression is important for hearing attention and protection from noise damage. We will test the hypothesis that cochlear type II sensory neurons provide the sensory input for this process using models where neuronal development is altered, or the neurons are removed. The study addresses hearing disability in society, facilitating cochlear prosthesis development and the understanding of hearing loss.
Early Indicators Of Noise Injury: Are Decreased Auditory Processing Skills Evident In Noise-exposed Adults Prior To Diagnosis Of Hearing Loss?
Funder
National Health and Medical Research Council
Funding Amount
$367,605.00
Summary
Recent research indicates that noise-exposed individuals with similar hearing thresholds to non-noise exposed counterparts are more likely to have diminished temporal and spectral auditory processing abilities. This research aims to determine the relationship between noise exposure levels and auditory processing difficulties; the influence of musical training in ameliorating these difficulties; and a neurological model of causation, operation and possible remediation of these difficulties.
Neurosteroid Modulation Of GABA-inhibition In Vivo: Central Auditory Pathway Models
Funder
National Health and Medical Research Council
Funding Amount
$331,650.00
Summary
All neurons at higher levels of the central nervous system signal in response to the outcome of various excitatory and inhibitory inputs (synapses) from other neurons. Most of the fast-acting inhibition is mediated by chloride ion influx through a channel which is gated by the neurotransmitter GABA. Termed the GABAa-receptor, this channel is known to be modulated by a wide range of pharmacological agents (e.g. valium; ethanol, many anaesthetics) which may enhance or suppress its efficacy. There ....All neurons at higher levels of the central nervous system signal in response to the outcome of various excitatory and inhibitory inputs (synapses) from other neurons. Most of the fast-acting inhibition is mediated by chloride ion influx through a channel which is gated by the neurotransmitter GABA. Termed the GABAa-receptor, this channel is known to be modulated by a wide range of pharmacological agents (e.g. valium; ethanol, many anaesthetics) which may enhance or suppress its efficacy. There are also good reasons for concluding that there is a capacity for modulation by endogenous substances. Brain synthesized steroids (neurosteroids) are known to have a potent enhancement effect upon the efficacy of GABAa-receptors, and have been implicated in a number of clinical situations, including menstrual cycle related depression. Work of others has shown that rapid synthesis of neurosteroids acts to increase inhibition in response to anxiety-inducing stimuli. Our recent work has shown that neurosteroids mediate an induced increase in inhibition in the auditory midbrain area. A surprising aspect of that study was that neurosteroids also appear to mediate ongoing levels of inhibition. This now allows us to use the many inhibitory interactions in the auditory pathway as potential models for studying the role of neurosteroid modulation of GABA inhibition in normal brain function. This is important because a number of medical treaments have the side effect of changing the synthesis of neurosteroids. We will also use an auditory system model of neurotrauma to examine the role of neurosteroids in increasing inhibition (to counter a potentially lethal increase in excitability). The work will involve electophysiological functional measurements and the development of highly sensitivity analytical protocols using an electrospray mass spectrometer for direct measurement of neurosteroids in submicrogram samples of brain tissue.Read moreRead less
Temporal Processing In The Superior Olivary Complex: Impact Of Deafness And Peripheral Electrical Stimulation Strategies
Funder
National Health and Medical Research Council
Funding Amount
$225,500.00
Summary
The brain can use timing or temporal information to extract the frequency and location of sound. Timing information is coded by the pattern of responses of brain cells that match the period of the sound wave. These responses can be measured as small voltage spikes or action potentials. Integration of these responses from one brain-processing site to another relies on precise (temporally matched) firing among a population of cells that are activated in response to sound. Sound localisation relies ....The brain can use timing or temporal information to extract the frequency and location of sound. Timing information is coded by the pattern of responses of brain cells that match the period of the sound wave. These responses can be measured as small voltage spikes or action potentials. Integration of these responses from one brain-processing site to another relies on precise (temporally matched) firing among a population of cells that are activated in response to sound. Sound localisation relies on this temporal integration from information coming from both ears. Specifically, the integration of this information relies on the balance of incoming inputs from both ears, which maintains an appropriate time window depending on the location of sound in space. Recent evidence suggests that in deafness this process of integration is disrupted which may be possibly due to an inability to regulate the coherent activation of cells. This has implications for cochlear implant users whose ability to process temporal information is compromised by a loss of temporal coding ability resulting from prior deafness. In this project we will measure voltage changes occurring inside cells of the superior olivary complex, which contains a group of structures that integrate input from both ears. We will examine the ability of these cells to process temporal information in normal and deafened conditions. This study will lead not only to an understanding of basic mechanisms for auditory coding but also to improved electrical stimulation strategies for patients with cochlear implants.Read moreRead less
Effects Of Increased Endolymph Volume On Cochlear And Vestibular Function And Morphology Of Inner Ear Tissues
Funder
National Health and Medical Research Council
Funding Amount
$313,391.00
Summary
Our recent research suggests that the vertigo attacks associated with enlarged fluid volumes in the inner ear, in diseases such as Ménière's Disease, maybe triggered when the fluid pressure forces open tissue valves located in the fluid-ducts connecting the hearing and balance organs. This project aims to identify the functional role of these valves, and to develop an animal model of abrupt changes in vestibular activity due to hydrops, to allow future treatments to be developed.
Auditory Processing Deficits In Specific Language Impairment And Specific Reading Disability:Their Effects And Treatment
Funder
National Health and Medical Research Council
Funding Amount
$314,250.00
Summary
One possible cause of specific language impairment (SLI) and specific reading disability (SRD; commonly known as dyslexia) is an inability to discriminate between sounds. Such an impairment could affect the ability to discriminate between simple speech sounds (phonemes) which are the basic building blocks for developing spoken language and reading skills. How many children with SLI or SRD have poor sound discrimination? What pattern of spoken language and reading impairments do these children ha ....One possible cause of specific language impairment (SLI) and specific reading disability (SRD; commonly known as dyslexia) is an inability to discriminate between sounds. Such an impairment could affect the ability to discriminate between simple speech sounds (phonemes) which are the basic building blocks for developing spoken language and reading skills. How many children with SLI or SRD have poor sound discrimination? What pattern of spoken language and reading impairments do these children have as a result of this impairment? Can poor sound discrimination be fixed? If it can, does it improve spoken language and reading impairments? And if it does, does it have an immediate effect or does it take some time to make a difference? These are some of the questions that will be addressed by this research. The answers will help us develop a training program that focuses specifically on improving the sound discrimination abilities of children who really need it. This will be a more efficient and inexpensive (if not free) than the Fast ForWord program that trains multiple non-verbal and verbal processing abilities regardless of whether a child has an impairment in all (or any) of these abilities and is therefore time consuming (approximately 80 hours) and expensive (approximately $AUD2000). The data will also help up better identify the spoken and written language profiles that characterise children who have sound discrimination deficits so we can better predict whether they would benefit from training programs such as Fast ForWord. And the data will tell use whether impaired sound discrimination can be used to predict whether infants might be at risk for later spoken language and reading problems.Read moreRead less
Organization And Function Of Primate Auditory Cortex
Funder
National Health and Medical Research Council
Funding Amount
$271,671.00
Summary
The conscious perception of speech and other sounds depends on processing within a brain region known as the auditory cortex. Compared to other brain areas, relatively little is known about the organization and function of this structure. Recent studies have proposed that the auditory cortex may be anatomically subdivided into functional modules, each of which is specialized for processing different types of information. However, the evidence for multiple processing streams is fragmentary, and n ....The conscious perception of speech and other sounds depends on processing within a brain region known as the auditory cortex. Compared to other brain areas, relatively little is known about the organization and function of this structure. Recent studies have proposed that the auditory cortex may be anatomically subdivided into functional modules, each of which is specialized for processing different types of information. However, the evidence for multiple processing streams is fragmentary, and not entirely consistent. The proposed experiments will combine anatomical and physiological approaches to evaluate the functional organization of auditory cortex in the primate brain. We will map the electrical responses of single brain cells to various complex sounds across the brain surface, and inject dyes to label pathways linking brain areas to one another. The data will allow us to determine whether specific subdivisions of the auditory cortex are specialized for processing different types of infomation, and whether specific subdivisions are linked together to form processing streams specialized for sound recognition and space perception. The results will advance our understanding of the neuronal processing involved in the perception of sound, with possible implications for speech perception. This will help to understand the consequences of brain damage, and may inform the development of hearing aids and artificial voice recognition systems. In addition, this study will help to develop a primate model for studying brain mechanisms of sound recognition that should be useful in research on cochlear implants.Read moreRead less