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New technology will improve neuron activation induced by cochlear implants

Date:
July 17, 2013
Source:
Neural Regeneration Research
Summary:
Cochlear implants, electrical prosthetic devices that stimulate inner ear neurons of individuals who have lost their cochlear sensory cells, restore usable hearing to deaf patients.
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These are confocal images of spiral ganglion neurites co-cultured with neurotrophin-producing fibroblasts. As above, neurites were immunostained for neurofilament 200 (Texas Red) and FITC phalloidin was used to visualize actin in non-neuronal cells (green) under co-culture condition, spiral ganglion neurites appeared thicker in the presence of neurotrophin-producing fibroblasts. NT-3: Neurotrophin-3; BDNF: brain-derived neurotrophic factor.
Credit: Neural Regeneration Research

Cochlear implants, electrical prosthetic devices that stimulate inner ear neurons of individuals who have lost their cochlear sensory cells, restore usable hearing to deaf patients. Cochlear implant electrodes are placed in the fluid-filled scala tympani of the cochlea, at a significant distance from the spiral ganglion and even from the spiral ganglion dendrites.

Stimulation via a cochlear implant electrode pair is therefore likely to activate large numbers of neurons concurrently. This may decrease the resolution and dynamic range of information transmitted in patients with cochlear implants. The low precision of electrical neural activation, compared to the precise activation that occurs in the normal cochlea, may explain why increasing the number of electrodes on a cochlear implant beyond 8–10 does not improve functionality.

However, if cochlear neurons could be induced to extend neurites toward a cochlear implant, it might be possible to stimulate more discrete subpopulations, and to increase the resolution of the device. Prof. Allen F. Ryan and colleagues from University of California exposed spiral ganglion explants from neonatal rats to soluble neurotrophins, cells transfected to secrete neurotrophins, and/or collagen gels.

Researchers found that cochlear neurites grew readily on collagen surfaces and in three-dimensional collagen gels. Co-culture with cells producing neurotrophin-3 resulted in increased numbers of neurites, and neurites that were longer than when explants were cultured with control fibroblasts stably transfected with green fluorescent protein.

It is suggested that extracellular matrix molecule gels and cells transfected to produce neurotrophins offer an opportunity to attract spiral ganglion neurites toward a cochlear implant.


Story Source:

The above post is reprinted from materials provided by Neural Regeneration Research. Note: Materials may be edited for content and length.


Journal Reference:

  1. Xie J, Pak K, Evans A, Kamgar-Parsi A, Fausti S, Mullen L, Ryan AF. Neurotrophins differentially stimulate the growth of cochlear neurites on collagen surfaces and in gels. Neural Regen Res., 2013;8(17):1541-1550 DOI: 10.3969/j.issn.1673-5374.2013.17.001

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Neural Regeneration Research. "New technology will improve neuron activation induced by cochlear implants." ScienceDaily. ScienceDaily, 17 July 2013. <www.sciencedaily.com/releases/2013/07/130717095526.htm>.
Neural Regeneration Research. (2013, July 17). New technology will improve neuron activation induced by cochlear implants. ScienceDaily. Retrieved September 4, 2015 from www.sciencedaily.com/releases/2013/07/130717095526.htm
Neural Regeneration Research. "New technology will improve neuron activation induced by cochlear implants." ScienceDaily. www.sciencedaily.com/releases/2013/07/130717095526.htm (accessed September 4, 2015).

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