聲音的遮蔽效應發生在當背景雜訊干擾目標聲音的判斷時。本論文將藉由設計持續的雜音加上較短的音調為聲音輸入，並將此導入現有之聲學模型中，此聲學模型包含中耳、耳蝸的流體力學模型、外毛細胞、內毛細胞、聽覺神經、T型多極細胞，並以此模型模擬遮蔽效應。接著提出內側橄欖耳蝸反射之模型，並模擬去遮蔽效應。去遮蔽效應為將遮蔽效應減弱的機制，有助於聽覺辨識。本內側耳蝸橄欖迴路建立的機制參考生物實驗的外毛細胞實驗結果：將乙醯膽鹼此神經傳遞值施用於外毛細胞上，會使外毛細胞的電導上升。本模型以內側橄欖耳蝸接受刺激後增加外毛細胞的電導，減少外毛細胞的放大作用，達到去遮蔽現象。接著提出垂直細胞膜型，並觀察此模型對去如何影響遮蔽效應。垂直細胞位於背側耳蝸核，抑制位於附側耳蝸核的T型多極細胞，本垂直細胞模型以增加T型多極細胞被觸發的閾值方式模擬被抑制的機制。垂直細胞有一特性：對於雜訊的反應較小。因此垂直細胞模型加入側抑制以模擬此現象。最後設計另一組持續音調在持續雜音中為聲音輸入，並再次模擬遮蔽與去遮蔽效應。

The masking effect happens when the background noise influences the target sound, which is then difficult to be perceived. To simulated this effect, we constructed a tone-burst-in-noise stimulus, and then fed into the model comprised of middle ear, cochlear membrane-fluid system, outer hair cell (OHC), inner hair cell (IHC), auditory nerve (AN), T-multipolar (TM) cell. This model successfully simulated the masking effect especially in low-level region. The medial olivocochlear reflex (MOCR), a descending auditory pathway, induces the anti-masking effect to reduce the masking effect and help human to perceive sounds. Based on an experiment of the OHC which showed the conductance of OHC was increased after applying acetylcholine (ACh), we have constructed the MOC model by changing the conductance of OHC and simulated the anti-masking effect. The tuberculoventral (TUB) cell is an inhibitory interneuron in dorsal cochlear nucleus (DCN) and projects to the ventral cochlear nucleus (VCN). The TUB inhibits the interneuron in VCN, and is sensitive to tones, while not to noise. We have used these two properties to construct a TUB model and enhance the anti-masking effect in sustained tone-in-noise conditions.

Abstract i
Acknowledgements ii
Contents iii
List of Figures v
List of Tables vi
Abbreviations vii
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 What is a Biophysical Model? . . . . . . . . . . . . . . . . . . . . . 3
1.2.2 Research Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.3 Liu and Neely Model [1][2] - Middle Ear, Basilar Membrane, and
Outer Hair Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.4 Sumner et al. Model [3] - Inner Hair Cell and Auditory Nerve . . . 5
1.2.5 Hewitt et al. Model [4] - T-Multipolar Cell . . . . . . . . . . . . . 5
1.2.6 Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Peripheral Auditory System 7
2.1 Outer Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Middle Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Inner Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3.1 Cochlear System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3.2 Place Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3.3 Outer Hair Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.4 OHC Mechanoeletrical Transduction . . . . . . . . . . . . . . . . . 14
2.3.5 OHC Electromotility . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.6 State-space Formulation . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.7 Inner Hair Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3.8 IHC Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.3.8.1 IHC Receptor Potential . . . . . . . . . . . . . . . . . . . 17
2.3.8.2 Calcium Controlled Transmitter Release Function . . . . 19
Contents iv
2.3.8.3 Quantal and Probabilistic Model of Synaptic Adaptation 20
2.3.9 Auditory Nerve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3 Higher Auditory Pathway 22
3.1 Masking Eects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.1.1 Model Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.1.2 Simulation Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.1.3 Experiment Result . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2 Cochlear Nucleus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.1 Dendrite Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.2.2 Soma Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.3 Anti-Masking Eects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.3.1 Experiment results of the article: Feedback Control of The Auditory
Periphery: Anti-masking Eects of Middle Ear Muscles VS.
Olivocochlear Eerents [5] . . . . . . . . . . . . . . . . . . . . . . . 30
3.3.2 Construction of an MOC Model to Simulate the Anti-masking Eect 32
3.3.3 Experiment Result . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.4 The Tuberculoventral Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.4.1 Construction of a TUB Model . . . . . . . . . . . . . . . . . . . . . 37
3.4.2 Inhibiting the TM interneuron in the VCN . . . . . . . . . . . . . 38
3.4.3 Lateral Inhibition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.5 Simulate Sustained Tone-in-Noise Condition . . . . . . . . . . . . . . . . . 40
3.5.1 Stimulus Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.5.2 Experiment Results . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4 Conclusion 43
4.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
A Parameters 45
B State-space Formulation of Liu and Neely Model 49
B.1 Equation (2.19) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
B.2 Equation (2.22) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
B.3 Equation (2.21) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
B.4 Equation (2.20) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
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