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对时序信号的区分程度以及实验结果对生理和心理的影响。通过对耳蜗的时序电刺激获得的时间分辨率被发现上级通过听觉刺激和将频谱模式转换为时间的语音处理方法获得的时间分辨率。发现顺序信号对于将语音信息传递到听觉神经是有效的。此外，根据阈下电刺激耳蜗可以抑制耳鸣的结果，设计了植入式耳鸣抑制器，并应用于三名耳鸣患者。以下是研究结果的摘要。（1）听觉障碍者耳蜗电刺激时间分辨力为150 μ s左右，其中一名患者在未经训练的情况下，能分辨5个转换成时间序列刺激的元音，正确率为60%。（2）对300多名耳鸣患者进行耳鸣抑制试验，结果发现30%的患者耳鸣消失，63%的患者耳鸣减轻。（3）根据SOUID、EEG和血流量的测量，推测自主神经系统的副交感神经变得上级，脑干和边缘系统变得活跃。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，可以预期的是，通过长期使用植入式耳鸣抑制器，部分信号处理机制将变得清晰。随着植入技术的建立和生物相容性的证明，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.