- 學位論文
建立中耳至腦幹之聽覺生理模型並利用特定頻率延遲之tuberculoventral抑制模擬耳蝸反遮蔽效應
Establishing a biophysical auditory model from middle ear to brainstem and simulating the unmasking response of cochlea by delayed, frequency specific tuberculoventral inhibition
摘要
本論文欲建立一符合真實聽覺生理結構的生物物理模型，並期望藉由此模型模擬出多項符合真實人體聽覺之現象。以Liu and Neely於2009與2010年提出的中耳至內耳耳蝸與外毛細胞模型為基礎，串連多個已廣泛使用的聽覺生理模型(Meddis, 1986、Sumner et al., 2002、Hewitt et al., 1992)以及自行提出的新穎模型－特定頻率延遲抑制的Tuberculoventral細胞模型，建構出中耳至腦幹的聽覺迴路系統。 Tuberculoventral細胞與T型多極細胞在耳蝸核的分布均為tonotopic的型式，故不同位置有不同的最佳共振頻率， Tuberculoventral細胞可對相同特徵頻率點的T型多極細胞進行延遲性的抑制。若輸入聲刺激為一純音且低頻，在對應的特徵頻率點處聽覺神經會規律性的觸發而具有相位鎖定特性。因Tuberculoventral細胞與T型多極細胞的輸入均來自同一組的聽覺神經，故藉由Tuberculoventral細胞提供的特定頻率延遲抑制，可針對T型多極細胞相位鎖定周期上的穩定觸發進行抑制。又因內側橄欖－耳蝸中繼神經元的輸入來自T型多極細胞，此抑制便會降低內側橄欖－耳蝸中繼神經元的觸發次數，間接降低其提供給耳蝸的遮蔽效應。若輸入聲刺激為不規律之底噪，因其不具有相位鎖定特性，Tuberculoventral細胞無法針對T型多極細胞提供有效抑制，使內側橄欖－耳蝸中繼神經元提供給耳蝸的遮蔽效應不受影響。此抑制上的差異便可對底噪與純音進行不同程度的遮蔽，模擬出內側橄欖－耳蝸中繼神經元提供給耳蝸的反遮蔽效應。
並列摘要
This thesis describes efforts to establish a biophysical model which corresponds to the real physiological structure of the auditory system. By using this model, a lot of phenomena in true human hearing can be simulated. Based on the models of the middle ear to the cochlea and outer hair cells (Liu and Neely, 2009, 2010), we integrate several auditory models (Meddis, 1986; Sumner et al., 2002; Hewitt et al., 1992) and a new model－a tuberculoventral(TUB) cell model with delayed, frequency-specific inhibition－to construct the auditory pathway from middle ear to the brainstem. In the cochlear nucleus, TUB cells and T-multipolar cells are distributed tonotopically. In other words, every TUB cell and T-multipolar cell in different place has its own best resonance frequency. The T-multipolar cell can be inhibited by TUB cell which has the same best resonance frequency. If the acoustic stimulation is a pure tone of low frequency, the corresponding auditory nerve fibers will fire regularly and generate a special effect called phase locking. Because TUB cells and T-multipolar cells receive input from the same group of auditory nerve fibers, the delayed, frequency-specific inhibition of TUB cells can suppress the stable triggering in the phase locking cycle of T-multipolar cells. Since the input of medial olivocochlear(MOC) interneurons are from T-multipolars, this inhibition can lower the firing rate of MOC interneurons and cause the masking effect in the cochlea to reduce indirectly. If the acoustic stimulation is irregular background noise, there is no phase locking effect, so the TUB cells can not inhibit the T-multipolars effectively. Therefore the masking effect in the cochlea from MOC interneurons will be unaffected. The discrepancy of the inhibition from TUB cells can cause different masking intensity between background noise and pure tone, so the unmasking effect in the cochlea from MOC interneurons can be simulated.