根據虛擬電極之人工電子耳刺激策略的神經生理研究

Abstract

國外研究指出在安靜環境中，人工電子耳使用者只需要6 至9 個有效的頻道就有足夠聽力聽到大多數英語談話。但是目前人工電子耳系統只有16 或24 電極是不足夠給人工電子耳使用者聽(或欣賞)音樂、聽國語或在吵雜環境中使用。本計劃利用主持人創新的虛擬電極技術。此技術提升人工電子耳電極之數目從 16 或24 個到250~1000 個虛擬電極，20 倍至40 倍增加頻率解析度。這將有效的提升傳送到聽神經之頻譜信息(spectral cues)。同時將發展基於新的虛擬250~1000電極系統之刺激策略(stimulating strategy)，增加送到聽神經之時域信息(temporal cues)。最新的研究指出增加頻譜信息與時域信息能增進人工電子耳使用者在吵雜環境中、聽音樂、聽國語等聽力的效能。因為現今使用的人工電子耳的電極數目有限，無法將足夠的頻率訊息傳遞給聽神經，使得人工電子耳的功效仍然有限。若能有效的增加電極的數目，將會顯著的提升現行人工電子耳的功能。本計劃的主持人在過去國科會的研究計畫中，已經成功的研發出一種新的刺激策略；利用此一研究策略，可以將目前使用的人工電子耳的電極數，從目前使用的16 或24 個實體電極，增加成250 甚至是1000 個虛擬電極。因此，一研究成果若能早日應用在人工電子耳上，將會顯著提升使用人工電子耳病患聽的品質。所以，本計畫的目標就是要將本計畫主持人過去的研究成果，更進一步的在實驗動物上，進行新一代刺激策略對神經電生理等相關特性之影響進行研究與探討本計畫將會評估和比較，新的刺激策略與傳統刺激策略對於實驗動物的聽神經元之電生理反應特性的影響。除此之外，動物實驗的研究結果，也會進一步的與先前的數據模擬成效比較，來找出究竟是哪些刺激參數可以有效的提升人工電子耳的功效。為了協助此一計畫的執行，本計畫將會建立一個新的人工電子耳研發平台。

Though cochlear implants have been commercially available products, there are still a lot of questions regarding how to improve the hearing capability of cochlear implant (CI) patients. The two major factors that affect the hearing performance of CI patients are temporal cues and spectral cues they receive. While it is possible to increase the temporal cues by increasing the electrical stimulating rate, the spectral cues the CI patients receive is limited by the number of electrode contacts implanted in the CI patients. The current available number of electrode contacts in a cochlear prosthesis system is 16 or 24, which is equivalent to 8 or 12 bipolar channels. Research shows that while 6 to 9 effective channels are sufficient for hearing and understanding English speech in quiet environment, however, it is not enough for listening to speech in noise, music and tonal language, particularly Mandarin Chinese. Previously, the principal investigator (PI) proposed in an earlier National Science Council (NSC) research project to raises the number of cochlear implant electrodes effectively from 16 or 24 real electrodes to 250~1000 virtual electrodes by means of new stimulating strategies based on 4-electrode current steering, thus dramatically improve the spectral cues delivered to the auditory nerves. In this project, animal neuro-physiology studies using the new stimulating strategies will be studied. Engineering experiments on electric current spread will be studied with the 2-electrode current steering and 4-electrode current steering to validate the PI’s NSC modeling work and his preliminary version of 250 virtual electrodes stimulating strategies based on 4-electrode current steering. These new CI stimulating strategies will be tested against traditional CI stimulating strategies, e.g. complementary interleave sampling (CIS), Hi-Res, in neurophysiology animal studies. Neuro-physiological animal experiments will be compared with numerical modeling results to identify the stimulating strategy parameters that would improve performance. A new cochlear prosthesis research platform will be set up to facilitate this study.