Medicine, Dentistry and Health SciencesDepartment of Otolaryngology

Auditory Nervous System Function after Treatment with Trophic Agents

Principal investigator

Dr David Sly

Background

The success of the cochlear implant is dependent upon the integrity and function of the auditory nerve. In a healthy ear, the auditory nerve is normally maintained by the release of nerve growth factors from hair cells, but when these are lost in deafness, there is severe degradation of the auditory nerve with time. However, the application of nerve growth factors to the deafened cochlea arrests hearing nerve degeneration and is potentially of major importance to cochlear implantation.

This project examines how biological interventions with nerve growth factors can affect the structure of the auditory nerve and its response to cochlear implant stimulation. We are particularly interested in deciphering how longer periods of deafness and of neurotrophin treatment and how varying dosages of neurotrophins affect these outcomes so they may be understood prior to clinical application of nerve growth factors.

Figure: Illustration shows the degeneration in the auditory nerve that occurs following the loss of the cochlear hair cells. Our studies aim to halt this structural and functional damage with the application of neurotrophins to the nerves.

Research aims

The specific aims of this project are to determine:

  • If trophic stimulation produces deleterious or beneficial effects upon neural structure and function throughout the auditory nervous system
  • How neurotrophin treatment in normal hearing animals affects the hearing
  • How the duration of deafness (up to 15 weeks) prior to trophic treatment affects auditory function
  • How the duration of neurotrophin treatment (up to 12 weeks) after deafness affects auditory function
  • How the neurotrophin dose effects of auditory nerve function
  • How neurotrophins affect the molecular structure of the auditory nerve

Figure: Shows the distribution of a potassium ion channel in the neurons within the cochlea. These ion channels are altered after deafness which in turn may alter neural function. Our research will determine if neurotrophins can halt these changes.

Techniques

  • Cochlear implant surgery
  • Single neuron electrophysiology
  • Cochlear and auditory brain histology
  • Fluorescent and light digital microscopy

Staff

Collaborators

Students

  • Ms Amy Hampson (Honours)
  • Mr Matthew Ng (AMS)
  • Ms Jingnan Zhang (AMS)
  • Tass Kourkoulis (Master of Audiology)
  • Stanley Xie (Master of Audiology)
  • Alexander Benski (Master of Audiology)

Support Staff

  • Mr Rodney Millard (Engineering)
  • Mr Frank Nielsen (Engineering)
  • Ms Elisa Borg (Husbandary)
  • Ms Helen Feng (Electrode Manufacture)
  • Ms Maria Clarke (Histology)
  • Ms Prue Nielsen (Histology)

Funding

  • National Health and Medical Research Council
  • The Royal Victorian Eye and Ear Hospital

Recent Publications

  • Campbell, L.J., Sly, D.J., O'Leary, S.J. Prediction and Control of the Stochastic Neuronal Response to Pulsatile Electrical Stimulation. Submitted Eur J Neurosci, Dec 2008.
  • Sly DJ, Heffer LF, White MW, Shepherd RK, Birch MG, Minter RL, Nelson NE, Wise AK, O'Leary SJ. Deafness alters auditory nerve fibre responses to cochlear implant stimulation. Eur J Neurosci. 2007 Jul;26(2):510-22. Access Full Article

 

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