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
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
Both hearing and balance are vulnerable during ear surgery, and the loss of either carries a heavy personal, social and economic cost. We will develop new ways of protecting the ear during surgery, though the local delivery of medication to the inner ear. The protocol will be developed in the laboratory and tested in a clinical trial. This research will stand to benefit all people undergoing major operation on their ear, and especially cochlear implant candidates with residual hearing.
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
Cell-based Neurotrophin Delivery With Cochlear Implantation For Long-term Rescue Of Auditory Neurones Following Deafness
Funder
National Health and Medical Research Council
Funding Amount
$437,212.00
Summary
This project aims to develop safe and effective techniques for long-term delivery of drugs to the ear by genetically modifying cells so they release the theraputic agents over extended periods of time, and then to use encapsulation techniques to safely deliver these cells to the inner ear in combination with a cochlear implant.
Evaluating Perceptual Benefits Of Bilateral Cochlear Implants For Young Children And Infants
Funder
National Health and Medical Research Council
Funding Amount
$452,843.00
Summary
The cochlear implant (bionic ear) has revolutionised communication for children with profound hearing loss. Nevertheless, children with the standard single implant still face huge challenges in educational and social settings. Difficulties include understanding speech that is soft, or speech in noisy environments, such as the classroom. Also, with one implant, children cannot locate the source of sound, such as the speaker in a group conversation, team-mates during sport, or an oncoming car. Res ....The cochlear implant (bionic ear) has revolutionised communication for children with profound hearing loss. Nevertheless, children with the standard single implant still face huge challenges in educational and social settings. Difficulties include understanding speech that is soft, or speech in noisy environments, such as the classroom. Also, with one implant, children cannot locate the source of sound, such as the speaker in a group conversation, team-mates during sport, or an oncoming car. Research with other normal hearing and hearing impaired groups suggests that two (bilateral) implants may possibly improve performance in these conditions. Although hundreds of children worldwide have received bilateral implants, very limited evidence is available to indicate whether two implants are significantly better than one, especially for young children. The main aim of the research is to evaluate the improvement in listening performance when young children and infants use two implants as compared with one. An additional aim is to gain clinical knowledge of bilateral implant use in order to develop selection criteria and management protocols for young bilateral candidates in the future. Results of this research will determine if bilateral implants should become a standard option for young children at the RVEEH-University of Melbourne Implant Clinic. The results will be published and presented internationally to influence clinical practice worldwide. All children using a cochlear implant, or in need of one in the future, will benefit as the study outcomes will indicate the best choice of hearing devices for individual children, and help to determine best-practice management if bilateral implants become an option for all children.Read moreRead less
Improving Speech Perception Outcomes In Deaf Adults And Children Using Cochlear Implants
Funder
National Health and Medical Research Council
Funding Amount
$160,604.00
Summary
This project aims to further improve on speech understanding by deaf adults and children using the cochlear implant. In particular, we aim to individually modify the speech coding scheme on the basis of the basic hearing skills of the subject. In this manner, more speech information should be available and the users will likely gain more benefit from their cochlear implants. The speech processing strategy of the multiple-electrode cochlear implant, manufactured by the Australian biomedical compa ....This project aims to further improve on speech understanding by deaf adults and children using the cochlear implant. In particular, we aim to individually modify the speech coding scheme on the basis of the basic hearing skills of the subject. In this manner, more speech information should be available and the users will likely gain more benefit from their cochlear implants. The speech processing strategy of the multiple-electrode cochlear implant, manufactured by the Australian biomedical company Cochlear Limited, codes acoustic frequency information on electrodes which are located in the cochlea. The assignment of frequencies to electrodes is consistent with the ordering of pitch in the cochlea. For optimum performance, all electrodes would need to be perceptually distinct from each other. Recent research with adults and children has shown that this is not the case for a number of subjects as adjacent electrodes sound the same. Thus important speech information may not be heard by these subjects. In this project, we will determine how well adults and children are able to hear differences between the electrodes, and then provide speech processing schemes which exclude those electrodes which sound the same as others in close proximity. The project will compare these modified strategies with the standard strategy currently used by the subjects over time, so that any differences in the way adults and children are able to improve on speech understanding will be determined. As far as can be determined, this project will be the first investigation to improve on speech understanding in children using the cochlear implant.Read moreRead less