The Mechanosensory Representations in the Drosophila Higher Brain Centers

果蠅腦內機械感知神經網路圖譜

羅士杰(Shyn-Jie Lou)

指導教授 ： 江安世

國立清華大學/生命科學院/生物科技研究所/碩士(2009年)

摘要

為了理解大腦如何接收、比較和運算各種感覺傳入的訊息，我們必需了解各個神經網路在腦中運作時所扮演的角色。利用果蠅當作模式生物去研究大腦的功能，嗅覺神經是一個最熱門同時也是目前最了解的系統，然而在果蠅其他的大腦感知神經系統中，我們知道的仍然不多。機械感知神經系統在果蠅中參與了聲音的接收、風和重力的感受。在此，我們研究果蠅腦中機械感知神經網路，其中包括了聽覺神經網路、重力感知神經網路和風感知神經網路。以上所有的機械感知神經都位於果蠅觸角的第二節，被稱為「強斯頓器官」。果蠅利用這部位可以感受到機械性的訊息，並且送到腦中「觸角機械感知和運動中樞」。雖然聽覺神經網路在從觸角傳到腦中的第一層已經被研究清楚了，但是到腦中之後的神經網路仍然是一個謎。在這個研究中，我們利用光激發螢光蛋白這個技術去尋找可能的下游神經網路，並且用功能性影像分析去鑑定這些可能的神經是不是對於這些機械性刺激有反應。最後，我們找到了一種從單邊觸角機械感知和運動中樞連接到兩邊前腦下側區域的神經元，表示這個區域可能是處理機械感知訊息的第二站，相對於蕈狀體在果蠅嗅覺系統中的角色。我們更進一步地找到了四種形態上完全不同的神經元分佈於前腦下側區域，其中一種為局部調節神經，其他三種接收訊息後分別送到三個腦中更高階的處理區域。整理得到的結果，我們可以得到機械感知的訊息匯合於前腦下側區域，並且訊息又分散到至少三個以上不同的區域。這些將會幫助我們更了解機械感知神經組成的網路，並且知道訊息如何在果蠅腦中處理。

關鍵字

果蠅 ； 機械感知 ； 圖譜 ； 神經

並列摘要

To understand how a brain receive, compare, and process all kinds of sensory inputs, we have to identify every circuit involve in the processing pathway. By using Drosophila as a model system to study brain function, the olfactory system is the most popular topic and became a clearly understood system. However, little was known in other sensory pathway in the Drosophila brain. Mechanosensory system is involved in sensing sound, wind and gravity. Here, we study the mechanical sensory and processing circuits included auditory circuits and wind sensing circuits. All of these mechanosensory neurons were located in the secondary segment of antenna, called the Johnston’s organ (JO), detecting signals and projecting axonal terminals to a specific brain region--the antennal mechanosensory and motor center (AMMC). The signals are thus relayed from the antennae into the brain. Although the auditory circuits at the first level of are well known, the processing center at the next level is unclear in the Drosophila brain. In this study, we utilize the PaGFP technique to search candidate circuits involved in mechanical signal processing at the second level. Then, we used functional imaging to verify these candidate circuits do response to mechanostimulus. In this study, we found a bilateral neuron connect one side of the AMMC and send to the both side of caudo-ventrolateral protocerebrum (CVLP) regions indicating that the CVLP may act as a second level of mechanosensory center correspondence to the mushroom body in the Drosophila olfactory system. We further found four types of morphological distinct neurons innervate the CVLP region, one may act as local regulatory neurons and others receive signals and send to three different parts of higher brain regions. Taken together, our finding show the mechanosensory information is converged to the CVLP and diverged to at least three parts of higher brain regions. These will help us to understand how the mechaosensory circuits are constructed and signals processed in the Drosophila brain.

並列關鍵字

Drosophila ； mechanosensory ； Johnston's organ ； AMMC ； CVLP

參考文獻

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