Nerve pathways exist that carry information from the highest parts of the brain to the peripheral hearing organ, the inner ear. These descending control pathways have the potential to affect the hearing process in a number of ways; protecting from loud sounds, improving the detection of signals in noisy backgrounds, selecting stimuli of interest and regulating a variety of aspects of inner ear function. Abnormal function of these pathways can affect hearing sensitivity and may be important in ph ....Nerve pathways exist that carry information from the highest parts of the brain to the peripheral hearing organ, the inner ear. These descending control pathways have the potential to affect the hearing process in a number of ways; protecting from loud sounds, improving the detection of signals in noisy backgrounds, selecting stimuli of interest and regulating a variety of aspects of inner ear function. Abnormal function of these pathways can affect hearing sensitivity and may be important in phenomena such as tinnitus and other disorders of hearing. This project will investigate the subtle effects that selective activation of these pathways has on inner ear function and will attempt to unravel the different influences that subcomponents of the pathways have on the different aspects of hearing.Read moreRead less
Investigating The Potential Of Human Stem Cells To Repair The Degenerating Auditory Nerve After Deafness
Funder
National Health and Medical Research Council
Funding Amount
$310,787.00
Summary
One in four Australians is predicted to experience some form of hearing loss by 2050. Hearing loss is irreversible and the chief clinical treatment available for severe to profound hearing loss is a cochlear implant. However, cochlear implant efficacy is limited by the degeneration of the auditory nerve following hearing loss. Using stem cells, this project will develop techniques to restore function to the auditory nerve through replacement of the specialised cells that comprise it.
Cochlear Mechanisms Of Otoacoustic Emission Generation
Funder
National Health and Medical Research Council
Funding Amount
$311,989.00
Summary
Deafness, both congenital and acquired, is likely to be one of the major causes of disability in the Australian workforce, in young Australians, and in some categories of pre-term infants in the next decade or two. While not life-threatening, hearing impairment deprives individuals of one of their most basic social needs: the ability to communicate with others. Although little can be done to recover lost hearing, it is important to detect hearing loss as early as possible in order to reduce furt ....Deafness, both congenital and acquired, is likely to be one of the major causes of disability in the Australian workforce, in young Australians, and in some categories of pre-term infants in the next decade or two. While not life-threatening, hearing impairment deprives individuals of one of their most basic social needs: the ability to communicate with others. Although little can be done to recover lost hearing, it is important to detect hearing loss as early as possible in order to reduce further loss (by behaviour modification in the case of noise-exposed adults) and to provide hearing assistance in very young children so that they may be exposed to some degree of auditory experience at as early an age as possible. To this end, the phenomenon of otoacoustic emissions, or noises from the ear, now recognised for twenty years, is likely to become even more significant in the early years of the next millennium. Otoacoustic emissions were first demonstrated as very soft echoes re-emerging from the ear after a delay of ten milliseconds or so following a click stimulus. These echoes are sounds produced by the ear as it goes about its normal function and are lost if the hearing sensitivity of the individual is below normal. Several other forms of otoacoustic emissions have been discovered and rapidly applied to the testing of hearing so that today the technique of assessing hearing status in neonates and others unable to co-operate, as well as in diagnostic applications, is widespread. The application of the technique, however, has preceded a real understanding of what otoacoustic emissions are and how they are generated, and their widespread use at the moment is somewhat akin to a car repair industry which does not understand how an engine works. This proposal intends to investigate the basic mechanisms behind otoacoustic emissions in order to improve their efficiency and accuracy of clinical interpretation.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
Normal hearing relies on the generation and transmission of electrical signals in the hearing organ, the inner ear. These electrical signals are generated by the action of specialized molecular ion channels in the cellular membranes of the inner ear and this research aims to charcterize these ion channels and detail their role in the hearing process. The results will impact on our understanding of human hearing disorders such as tinnitus, auditory neuropathy and disturbances of loudness sensatio ....Normal hearing relies on the generation and transmission of electrical signals in the hearing organ, the inner ear. These electrical signals are generated by the action of specialized molecular ion channels in the cellular membranes of the inner ear and this research aims to charcterize these ion channels and detail their role in the hearing process. The results will impact on our understanding of human hearing disorders such as tinnitus, auditory neuropathy and disturbances of loudness sensation.Read moreRead less
Thalamic And Basal Forebrain Contributions To Auditory Cortical Reorganization Produced By Partial Hearing Loss
Funder
National Health and Medical Research Council
Funding Amount
$364,768.00
Summary
When part of the cochlea is damaged in adult animals, leading to a partial hearing loss, the auditory area of the cerebral cortex reorganizes itself, so that the area deprived of input by the peripheral lesion is not silent, but is occupied by expanded representations of adjacent frequencies. This reorganization has been observed in a number of species, including non-human primates, and it seems likely that it also occurs in humans with cochlear damage and hearing loss of this sort. If it does, ....When part of the cochlea is damaged in adult animals, leading to a partial hearing loss, the auditory area of the cerebral cortex reorganizes itself, so that the area deprived of input by the peripheral lesion is not silent, but is occupied by expanded representations of adjacent frequencies. This reorganization has been observed in a number of species, including non-human primates, and it seems likely that it also occurs in humans with cochlear damage and hearing loss of this sort. If it does, it would have important consequences for the way in which input from a hearing aid or cochlear prosthesis (bionic ear) is processed in the brain. This Project is designed to clarify the nature of the systems in the brain that contribute to this form of cortical plasticity, using an animal model. One aim is to determine whether the plasticity is intrinsic to the cortex or occurs in the pathways over which information is conveyed to the cortex. This will be assessed by determining whether such plasticity is also found in the auditory thalamus, the final subcortical auditory nucleus from which information is sent to the cortex. The second aim is to determine whether the occurrence of plasticity is controlled by modulatory influences from the basal part of the forebrain. Neurons in this area project to many parts of the cortex, and evidence from other sensory systems suggests that these projections exert a permissive function, allowing the cortex to reorganize when input is altered. This aim will be pursued by determining whether cortical reorganization occurs after hearing loss when this basal forebrain system is inactivated. The significance of these studies is that they will elucidate the way in which the brain reorganizes itself when it is confronted with altered input. This information is important for our understanding of normal auditory information processing mechanisms and of the way in which input from prosthetic devices is processed in the hearing-impaired.Read moreRead less
Improved Perception Of Temporal Information In Electrical Signals For Profoundly Deaf Users Of Cochlear Implants
Funder
National Health and Medical Research Council
Funding Amount
$170,440.00
Summary
The ultimate goal of this project is to improve the ability of cochlear implant users to understand speech. The way in which a speech signal varies in amplitude over time provides useful information to the listener about the content of the speech signal. Currently, the way that the acoustic signal amplitude is converted to electrical signal amplitude for cochlear implantees does not take into consideration the very significant loudness summation present in multiple-electrode electrical stimulati ....The ultimate goal of this project is to improve the ability of cochlear implant users to understand speech. The way in which a speech signal varies in amplitude over time provides useful information to the listener about the content of the speech signal. Currently, the way that the acoustic signal amplitude is converted to electrical signal amplitude for cochlear implantees does not take into consideration the very significant loudness summation present in multiple-electrode electrical stimulation. That is, when there are multiple sequential current pulses on different electrodes over a short time, the resultant loudness is greater than the loudness due to individual current pulses. The lack of consideration of loudness summation effects has led to the amplitude variations in the acoustic signal not being accurately represented in the loudness variation perceived by the cochlear implantee. This project aims to develop a practical way of more accurately representing speech signal amplitude fluctuations for cochlear implantees by studying the effects of loudness summation. A second aim of the project is to study the effects on perception of using differently-shaped current pulses from those currently used. There is evidence from physiology experiments that using different shapes might cause the electrical stimulation to activate a more narrowly-spaced set of auditory neurons for each electrode. The application of results of both these studies will lead directly to improved perception of speech and other sounds by cochlear implantees, thus improving their communication ability and quality of life.Read moreRead less