絕大多數的動物們具有先天性的聽覺行為反應，而這些行為反應是經由基因調控的神經網路所形成的。 在果蠅中，聲音是由觸角第二節的聽覺器官(Johnston’s organ) 神經接收訊息，並送到腦內的觸角機械感受與運動中心 (AMMC)。 在本篇論文中，我分析神經網路結構以及神經元與神經元之間的連結，我發現有五種不同的聽覺投射神經元 (auditory projection neurons) 連接三個不同的腦區，這三個腦區由低層到高層分別是觸角機械感受與運動中心 (AMMC)，內腹側前腦 (IVLP) 以及腹側前腦 (VLP)。這些聽覺神經元具有功能上的歧異性：AMMC-B1a神經元，AMMC-B1b神經元以及AMMC-A2神經元對聲音有不同的反應 (例如對不同頻率範圍產生反應); 我發現有一種左右對稱的聽覺投射神經元連接左右腦的內腹側前腦區會釋放抑制性神經傳導物質 (GABA); 此外，有一類型的IVLP-VLP神經元對所有的頻率會產生反應。 本研究發現果蠅腦內的聽覺傳遞路徑是經由觸角機械感受與運動中心傳送到內腹側前腦，經處理後再送到腹側前腦。

Most animals exhibit innate auditory behaviors driven by genetically hardwired neural circuits. In Drosophila, acoustic information is relayed by Johnston’s organ (JO) neurons from the antenna to the antennal mechanosensory and motor center (AMMC) in the brain. Here, by using structural connectivity analysis, I identified 5 distinct types of auditory projection neurons (PNs) interconnecting the AMMC, inferior ventrolateral protocerebrum (IVLP), and ventrolateral protocerebrum (VLP) regions of the central brain. These auditory PNs are also functionally distinct; AMMC-B1a, AMMC-B1b, and AMMC-A2 neurons differ in their responses to sound (i.e., they are narrowly tuned or broadly tuned); 1 type of audio-responsive IVLP commissural PN connecting the 2 hemispheres is GABAergic; and 1 type of IVLP-VLP PN acts as a generalist responding to all tested audio frequencies. My findings delineate an auditory processing pathway involving AMMC→IVLP→VLP in the Drosophila brain.

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