應用於聽覺刺激反應觀測之高可靠度可撓式電極設計、製作與驗證

Abstract

本研究設計一個16通道可撓性腦皮質層電極陣列，置放於大鼠大腦聽覺區皮質表面，用於探討大鼠受到不同頻率、強度之短純音誘發大腦聽覺神經區域反應，並藉由多通道神經訊號擷取裝置，同時記錄16個不同位置與參考點之間電壓差的腦皮質層訊號，再由後端訊號處理分析，了解各個不同通道、不同聽覺刺激訊號與其相對應腦區位置反應的關聯性。 為了減少電極製作與封裝的複雜度，本研究利用可撓式印刷電路的技術，以聚醯亞胺為基材，實現可承受高溫烘烤、彎曲之可撓式腦皮質層電極，並採用厚度12 µm的聚醯亞胺與金屬走線，提高電極強韌度，更可適用於加熱封裝，以提高電極封裝良率，並藉由粗糙的電極表面特性，降低電化學阻抗至7 ‒ 16 KΩ，降低訊號傳遞時造成的損耗，使得腦皮質層電訊號能夠順利傳遞到後端系統進行訊號處理與記錄。 在活體大鼠聽覺刺激實驗中，本研究所製作之電極，成功記錄到具有明顯差異之16通道的聽覺誘發電位的訊號，且在不同刺激頻率1 ‒ 16 KHz，通道訊號在高刺激頻率時訊號集中在前側，而低頻率刺激時訊號集中在後側。這些量測結果，有助於未來建立音調拓樸地圖。

This paper presents a 16-channel flexible electrocorticography (ECoG) electrode array to monitor rat’s auditory response under different auditory frequency and intensity. The proposed 16-channel sensor array was placed on auditory cortex and connected to multi-channel neural signal recording system for simultaneous ECoG recording and analysis in response to auditory stimulus with different frequencies. To simplify fabrication and packaging process of ECoG sensor, this work utilized flexible printed circuit (FPC) technology to make a flexible ECoG electrode array using polyimide (PI) substrate which can suffer from higher temperature than common polymer materials. Moreover, 12-µm thickness of metal wire and PI substrate are useful to intensify durability of the proposed electrode array and suitable for packaging in high temperature to promote yield rate. With rough surface electrode, the impedance of electrochemical impedance spectroscopy (EIS) can be lower to ~10 KΩ to decrease the transmission loss in signal path for post signal process and recording. In in-vivo experiments, the proposed sensor array implanted into rat’s brain can successfully record different 16-channel auditory evoked potentials under different stimulus frequency from 1 KHz to 16 KHz and different intensities from 10 dB to 70 dB. These results can be utilized for construction of tonotopic mapping in the future.