Study of time-sequential signal processing of auditory nerves using a cochlear implant

本研究的目的是探讨耳蜗电刺激能分辨出多大程度的时间序列信号，以及电刺激结果能产生什么样的生理和心理效应。时间序列电刺激耳蜗获得的时间分辨率优于听觉刺激，将频谱模式转换为时间序列信号的语音处理方法可以有效地将语音信息传递给听觉神经。根据阈下电刺激耳蜗抑制耳鸣的结果，设计了一种植入式耳鸣抑制器，并应用于3例耳鸣患者。以下是对研究结果的总结。(1)时间顺序电刺激听力受损者耳蜗和正常人耳蜗的时间分辨率约为150 μ s；在没有训练的情况下，患者对转换为时间序列刺激的5个元音的识别正确率为60%。(2)从300多名耳鸣患者的耳鸣抑制试验结果来看，30%的患者耳鸣消失，63%的患者耳鸣减少。(3)从SOUID、EEG和血流量的测量结果来看，自主神经系统副交感神经占优，脑干和边缘系统活跃。虽然本研究的目的是探讨听觉神经系统的信号处理机制，但主要结果来自耳鸣抑制试验。然而，期望通过长期使用植入式耳鸣抑制器来阐明部分信号处理机制。随着植入技术的建立和设备生物相容性的验证，将继续研究寻找语音信号的最佳信号转换方法。

The purpose of the research is to investigate what degree of tiem-sequential signals can be discriminated by cochlear electrical stimulation and what kind of physiological and psychological feefcts by the electrimental results, time resolution obtained by the time-sequential electrical stimulation to the cochlea was found to be superior to that by auditory stimulation and a speech processing method that spectral patterns are converted into time-sequential signals was found to be effective for transmitting the speech information to the auditory nerves. Furthermore, from the result that tnnitus was suppressed by subthreshold electrical stimulation to the cochlea, an implantable tinnitus suppresser was designed and adopted to three patients with tinnitus. The following is summary of research results.(1)Time resolution was found to be about 150 us from the test of time-sequential electrical stimulation to the cochlea of the hearing impaired and one of pa ; tients could discriminate 5 vowels converted into time-sequential stimuli at 60% correct rate without training.(2)From the results of tinnitus suppression tests by more than 300 persons with tinnitus, it was found that tinnitus disappeared at 30 % of patients and tinnitus reduced at 63%.(3)From the measurements of SOUID, EEG and blood flow, it was assumed that parasympathetic nerves of autonomic nervous system became superior, and the brainstem and the limbic system became active. Although the purpose of the research was to investigate the signal processing mechanism of auditory nervous system, main results were obtained from tinnitus suppression tests. However, it is expected that a part of signal processing mechanisms will be clarfied by the long term use of implantable tinnitus suppressers. As the implantation technique was established and the biocompatibility of the device was porven, the research will be continued to find the optimal signal conversion method of speech signals.