Otolaryngology - Research Publications
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ItemNo Preview AvailablePersonal reflections on the multichannel cochlear implant and a view of the future(JOURNAL REHAB RES & DEV, 2008)The multichannel cochlear implant is the first neural prosthesis to effectively and safely bring electronic technology into a direct physiological relation with the central nervous system and human consciousness. It is also the first cochlear implant to give speech understanding to tens of thousands of persons with profound deafness and spoken language to children born deaf in more than 80 countries. In so doing, it is the first major advance in research and technology to help deaf children communicate since Sign Language of the Deaf was developed at the Paris deaf school (L'Institut National de Jeunes Sourds de Paris) >200 years ago. Furthermore, biomedical research has been fundamental for ensuring that the multielectrode implant is safe as well as effective. More recent research has also shown that bilateral implants confer the benefits of binaural hearing. Future research using nanotechnology should see high-fidelity sound received, which would help deaf persons communicate in noise and enjoy music. Research should also lead to implants in ears with useful hearing.
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ItemPromoting neurite outgrowth from spiral ganglion neuron explants using polypyrrole/BDNF-coated electrodes(WILEY, 2009-10)Release of neurotrophin-3 (NT3) and brain-derived neurotrophic factor (BDNF) from hair cells in the cochlea is essential for the survival of spiral ganglion neurons (SGNs). Loss of hair cells associated with a sensorineural hearing loss therefore results in degeneration of SGNs, potentially reducing the performance of a cochlear implant. Exogenous replacement of either or both neurotrophins protects SGNs from degeneration after deafness. We previously incorporated NT3 into the conducting polymer polypyrrole (Ppy) synthesized with para-toluene sulfonate (pTS) to investigate whether Ppy/pTS/NT3-coated cochlear implant electrodes could provide both neurotrophic support and electrical stimulation for SGNs. Enhanced and controlled release of NT3 was achieved when Ppy/pTS/NT3-coated electrodes were subjected to electrical stimulation. Here we describe the release dynamics and biological properties of Ppy/pTS with incorporated BDNF. Release studies demonstrated slow passive diffusion of BDNF from Ppy/pTS/BDNF, with electrical stimulation significantly enhancing BDNF release over 7 days. A 3-day SGN explant assay found that neurite outgrowth from explants was 12.3-fold greater when polymers contained BDNF (p < 0.001), although electrical stimulation did not increase neurite outgrowth further. The versatility of Ppy to store and release neurotrophins, conduct electrical charge, and act as a substrate for nerve-electrode interactions is discussed for specialized applications such as cochlear implants.
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ItemNo Preview AvailableFast inhibition alters first spike timing in auditory brainstem neurons(AMER PHYSIOLOGICAL SOC, 2004-10)Within the first processing site of the central auditory pathway, inhibitory neurons (D stellate cells) broadly tuned to tonal frequency project on narrowly tuned, excitatory output neurons (T stellate cells). The latter is thought to provide a topographic representation of sound spectrum, whereas the former is thought to provide lateral inhibition that improves spectral contrast, particularly in noise. In response to pure tones, the overall discharge rate in T stellate cells is unlikely to be suppressed dramatically by D stellate cells because they respond primarily to stimulus onset and provide fast, short-duration inhibition. In vivo intracellular recordings from the ventral cochlear nucleus (VCN) showed that, when tones were presented above or below the characteristic frequency (CF) of a T stellate neuron, they were inhibited during depolarization. This resulted in a delay in the initial action potential produced by T stellate cells. This ability of fast inhibition to alter the first spike timing of a T stellate neuron was confirmed by electrically activating the D stellate cell pathway that arises in the contralateral cochlear nucleus. Delay was also induced when two tones were presented: one at CF and one outside the frequency response area of the T stellate neuron. These findings suggest that the traditional view of lateral inhibition within the VCN should incorporate delay as one of its principle outcomes.
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ItemResearch directions for future generations of cochlear implants.(Maney Publishing, 2004-09)Physiological and psychophysical research indicates that improved hearing in noise and music appreciation are likely with cochlear implants, with better reproduction of the fine temporospatial patterns of neural response in the auditory pathways due to phase differences in neuron firing patterns as the result of the basilar membrane travelling wave. An initial speech-processing strategy, to in part reproduce this information, is showing better frequency discrimination and musical perception. However, more exact reproduction is likely with a new generation electrode array which could involve the use of neurotrophins and inherently conducting polymers. The siting and design of this, as well as safety, needs further investigation before it is implemented.
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ItemElectrode-Cellular Interface(AMER ASSOC ADVANCEMENT SCIENCE, 2009-04-10)Electrode materials that facilitate interaction with living cells are crucial for the development of next-generation bionic devices.
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ItemLearning to understand speech with the cochlear implant(MIT Press, 2002)