Thalamic and basal forebrain contributions to auditory cortical reorganization produced by partial hearing loss

Funded Activity 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, 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.

Funded Activity Details

Start Date: 01-01-2001

End Date: 01-01-2003

Funding Scheme: NHMRC Project Grants

Funding Amount: $364,768.00

Funder: National Health and Medical Research Council

Research Topics

ANZSRC Field of Research (FoR)

Medical virology

ANZSRC Socio-Economic Objective (SEO)

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Other Keywords

Auditory cortex | Basal forebrain | Cochlear prosthesis | Hearing aid | Hearing loss | Neural plasticity | Partial deafness | Thalamus

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