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
In the normal process of hearing, the brain actively selects sounds of interest from competing background sounds. This normal auditory function is indispensible for children and adults to cope in non-optimal listening environments, however the mechanisms by which such performance is achieved are poorly understood. This project will investigate the nerve circuits that enable this to occur and will also investigate how these circuits malfunction in various types of partial deafness. The results wi ....In the normal process of hearing, the brain actively selects sounds of interest from competing background sounds. This normal auditory function is indispensible for children and adults to cope in non-optimal listening environments, however the mechanisms by which such performance is achieved are poorly understood. This project will investigate the nerve circuits that enable this to occur and will also investigate how these circuits malfunction in various types of partial deafness. The results will improve our understanding of how we detect sounds and the impact of hearing pathologies on this process.Read moreRead less
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
Most adults will have already sustained damage to the tiny connections between hearing cells and nerve cells; a missing link in their auditory pathway. There is no way to repair the damage and our hearing will worsen over time. We now have compelling evidence that a growth factor therapy to the inner ear restores the connections. We will deliver world-first data to justify and set the parameters for a clinical trial for a therapy to treat hearing loss for the first time.
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