嗅覺系統是演化過程中最古老，但被了解最少的感官系統，也是感官神經生物學中最具挑戰性的研究目標之一。儘管嗅覺系統的大量計算模型已經被提出了，但是它們並沒有考慮到生理學的多樣性，局部神經元的連結方式以及昆蟲觸角葉-昆蟲的主要嗅覺器官-中的一些最新發現。最近的研究表明，使用GABA拮抗劑可降低某些投射神經元（Projection Neurons）的反應，並且昆蟲對氣味脈衝頻率敏感，可用於定位氣味源。為了解釋這些觀察，我們提出了昆蟲觸角波的脈衝神經迴路模型。基於最近的解剖和生理學研究，我們在模型中包括了局部神經元（Local Neurons）的三種亞型 (sub-types) 以及突觸短期抑制（STD），並表明STD與局部神經元之間的相互作用導致了頻率敏感反應。我們進一步發現，投射神經元對GABA拮抗劑的意外反應是STD與突觸前抑制之間複雜相互作用的結果，這是增強對氣味刺激的敏感性所必需的。最後我們發現，如果嗅小球中局部神經元的神經支配遵循特定的模式，則氣味識別能力會得到改善。我們的研究結果表明，突觸前抑制（Pre-synaptic inhibition）和局部神經元的各種生理學和連結方式不是獨立的屬性，但它們的交互作用，在觸角葉的功能中發揮關鍵作用。

Studies have shown that input-output normalization is supposed to be caused by lateral inhibition(Olsen et al., 2010). However, by giving GABA antagonist or higher odor stimulus frequency in the same network can also induce output attenuation(Riffell et al., 2014). To solve the puzzle, I built a novel neural network model. Apart from applying already widely modeled local inter neuron sub-types, I included a new data based (Chou et al., 2010) sub-type that fires spontaneously and is suppressed by odor stimulus. The proposed model can explain the relationship between the function of local neuron innervation pattern and lateral inhibition, which lead to better odor discrimination in system scale. Further more we show that the interaction between short term depression and inter neuron inhibition can lead to odor frequency discrimination, which indicates distance discrimination.

Abstract……………………...…………………………………2
中文摘要……………………………………………………….3
Chapter 1 (introduction)…………………………………….….5
Chapter 2 (Material and Method)..…...…………...………...….8
Chapter 3 (Results) ....................................................................27
Chapter 4 (Discussion)…………………...…………...……….44
Reference …………………...………………………………....50
Supplementary data …………………...………………………54

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