听觉优先效应是确保听者在具有回声的复杂声环境中准确定位原始声源的重要生理机制。本项目主要研究豚鼠下丘内部抑制性调控网络在优先效应中的作用及机制。通过在体多通道细胞外记录技术观察麻醉及清醒状态下豚鼠下丘中央核神经元对标准优先效应刺激声的反应；此外，根据下丘不同亚区间的纤维联系，在下丘间联合及同侧下丘外侧和背侧皮质进行电刺激后，进一步电解毁损该区域，观察其对下丘中央核神经元优先效应反应的变化。在动物离体脑片上，电刺激下丘间联合及同侧下丘外侧和背侧皮质，观察下丘中央核放电及突触后电流、突触后电位的变化。通过此研究，可观察下丘不同亚区在优先效应中的作用，探明下丘内部抑制性调控网络的投射方向及递质情况，有利于进一步明确下丘内部抑制性调控网络在优先效应中的作用机制。

The precedence effect (PE) occurs when identical paired sounds in rapid succession are presented to the listener and the first arriving sound interferes with the auditory perception induced by the second sound. This auditory phenomenon is thought to resolve the competition between the initial sound and its reflections in an echoic environment and to make the listener accurately localize sound to achieve perfect speech intelligibility. Previous studies on the PE in the central auditory systems of a variety of species have demonstrated neuronal correlates in which the leading sound suppresses the responses of neurons that are spatially sensitive to lagging sounds; however, the underlying mechanisms remain unknown. Although some previous researches have recommended that the inhibitory processes contribute to the suppression of the lagging sound in the central auditory system, the direct evidences are insufficient and the neural mechanism of the PE is still unclearly. The inferior colliculus (IC) is a strategic relay station in the ascending and descending auditory system pathways，in which neurons demonstrate a sophisticated level of processing for complex sound signals. The object of this project is to investigate the mechanism of suppressive circuit within subdivisions in the inferior colliculus of awake guinea pig in PE. Under standard PE sound stimulus, multi-channel in vivo recording would be performed to record neuronal activity of central nucleus of IC from the anaesthetized and awake guinea pigs. According to the connections within the central nucleus, dorsal cortex and external cortex of IC, electrical stimulation or electrolytic lesions would be applied to the commissure of the IC, the dorsal cortex and external cortex ipsilaterally to the recording central nucleus through electrode array. We also investigate the affect on the electrical activity recorded in the central nucleus by the stimulation of the commissure, dorsal cortex and external cortex of IC with the whole-cell patch clamp in vitro. Through these studies, the effect of subdivisions in PE will be observed, and the details of suppressive circuit within subdivisions of IC will be investigated which will be helpful in revealing the the mechanism of suppressive circuit within subdivisions of IC in PE.