A primary cause of deafness is damage of receptor cells in the inner ear. Clinically, it has been demonstrated that effective functionality can be provided by electrical stimulation of the auditory nerve, thus bypassing damaged receptor cells. However, subsequent to sensory cell loss there is a secondary degeneration of the afferent nerve fibers, resulting in reduced effectiveness of such cochlear prostheses. The effects of neurotrophic factors were tested in a guinea pig cochlear prosthesis model. After chemical deafening to mimic the clinical situation, the neurotrophic factors brain-derived neurotrophic factor and an analogue of ciliary neurotrophic factor were infused directly into the cochlea of the inner ear for 26 days by using an osmotic pump system. An electrode introduced into the cochlea was used to elicit auditory responses just as in patients implanted with cochlear prostheses. Intervention with brainderived neurotrophic factor and the ciliary neurotrophic factor analogue not only increased the survival of auditory spiral ganglion neurons, but significantly enhanced the functional responsiveness of the auditory system as measured by using electrically evoked auditory brainstem responses. This demonstration that neurotrophin intervention enhances threshold sensitivity within the auditory system will have great clinical importance for the treatment of deaf patients with cochlear prostheses. The findings have direct implications for the enhancement of responsiveness in deafferented peripheral nerves. Hearing impairment is the most frequent disability of people in industrialized countries, affecting more than one in seven individuals. Most hearing loss is caused by destruction of the sensory cells within the cochlea of the inner ear. In mammals, the auditory cells do not regenerate, nor are there currently effective interventions for their repair. Moreover, in the auditory system, as in other afferent systems, degeneration of the auditory nerve occurs secondary to the loss of the inner ear sensory cells (hair cells), thus aggravating the functional impairment. In the severely and profoundly deaf, the cochlear implant (prosthesis) has been shown to provide an effective habilitative intervention. The cochlear prosthesis consists of one or more electrodes inserted into the fluid space of the inner ear. The implant operates by directly electrically stimulating the auditory nerve, bypassing damaged or missing sensory receptor cells. This device now provides significant speech understanding, with a score for everyday sentence understanding of about 80% without lip reading in the majority of patients implanted (so far more than 40,000 worldwide) (1-3). However, the cochlear prosthesis depends on remaining excitable auditory nerve fibers, and their loss severely compromises the effectiveness of the implant and the hearing benefits it provides. Studies show a clear relationship between the total number of viable auditory neurons available for stimulation and the performance of subjects receiving cochlear implant...

We have investigated band discontinuities and chemical structures of Al2O3 gate insulator films on n-type GaN semiconductor by photoemission and x-ray absorption spectroscopy. It is found that the solid phase epitaxy at the GaN crystal during annealing procedures at 800 °C leads to phase transformation of Al2O3 films from amorphous to crystalline. Changes in crystallographic structures closely correlate with the significant increase in conduction band discontinuity at the Al2O3/GaN interface, which suggests that epitaxial Al2O3 films on GaN semiconductor, free from grain boundaries of Al2O3 polycrystalline, hold the potential for high insulation performance.

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The surgical results of ossicular chain reconstruction using a hydroxyapatite prosthesis were evaluated in 106 ears of 101 patients who were followed up for > 5 years. Successful reconstruction was defined as: (1) postoperative air-bone gap of

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