感官訊號的編譯密切仰賴特化的神經網路結構。蕈狀體（mushroom body) 為果蠅的嗅覺記憶中樞，被廣泛作為探討生物如何將外界刺激編譯為高階行為認知的模式系統。然而過去中尺度層級的研究對於蕈狀體的網路架構支持截然不同的假說，分別為受先天遺傳決定的類型化結構，以及受後天學習決定的隨機化連結。透過分析果蠅半腦電顯資料庫 (FlyEM hemibrain dataset)，我們的研究指出嗅盞（calyx）中的三類凱恩神經（kenyon cell）藉由維持橫跨嗅覺系統的空間映射達成不同程度的輸入擴張，並形成混合式網路結構。我們藉由整合低階嗅覺中樞嗅覺刺激反應與腦神經組（connectome）以建構出蕈狀體氣味調變模型，成功預測給定氣味下的活體內蕈狀體腦區反應強度。混合網路架構分化三類凱恩細胞對分子化學特徵的偵測敏感性，並可能進一步決定蕈狀體輸出神經的先天調變機制。本篇研究提出新的生物神經網路結構以及提供混合架構對於編譯外界刺激為高階認知的潛在計算優勢。

Bio-signal encoding mechanisms are heavily determined by the architecture of underlying neural circuits. Mushroom body (MB) is the olfaction memory center of Drosophila. Previous studies support opposite perspectives to the upstream organization of MB, that is, completely random or stereotypic, based on experimental evidence of the connectivity at the mesoscopic level. Here we identify the hybrid network structure of Drosophila calyx that three Kenyon cell (KC) classes leverage different levels of input expansion by maintaining the spatial map across the olfactory system. We construct a simulation model of the MB tuning profile by integrating the response pattern of the receptor neurons with the connectome of olfactory system The model successfully predicts the odor-evoked activity of MB in the lobe region. The hybrid structure differentiates the chemical sensitivity of KCs and likely determines the innate tuning features of MB output neurons. Our results provide insights into the computational benefit of a calyceal hybrid network for translating molecular signals into higher-order perception.

ACKNOWLEDGMENT.................................................. i ACKNOWLEDGMENT(CHINESE).................................. ii ABSTRACT OF THE DISSERTATION............................... iv ABSTRACT OF THE DISSERTATION (CHINESE)................ v TABLE OF CONTENTS.................................................. vi CHAPTER 1 INTRODUCTION...................................... 1 CHAPTER 2 RESULT................................................. 5
1. Connectivity preference in the calyx.................................... 5
1.1 Quantification of the calyceal stereotype.................... 5
1.2 Sampling requirement for detecting global structure...... 10
1.3 Spatial constraint of PN-to-KC innervation................. 13
2. Odor representation of MB lobes......................................... 15
2.1 2.2 2.3
3. Innate 3.1 3.2
CHAPTER 3
Tuning profile of early olfactory processing................ 15 Chemically sensitive specificity of KC classes............. 17 Model validation with calcium imaging..................... 21
tuning profile of MBONs.......................................... 25 Simulation of odor evoked MBON response............... 25 Functional implication of the stereotypy mapping......... 27
DISCUSSION.......................................... 30
CHAPTER 4 METHODS............................................. 36 CHAPTER 5 REFERENCE........................................... 41 APPENDIX..................................................................44
1. Supplementary figures............................................44 2. Supplementary tables.............................................50

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