Behavioral and physiological studies of sound localization

描述(申请人提供)：本项目的总体目标是了解声音定位的神经机制。这些结果将帮助我们理解大脑如何整合来自两只耳朵的听觉信息，并产生头部、眼睛和耳朵的定向运动，以便对目标进行近距离的视觉和听觉检查。这些实验旨在测试听觉脑干中出现的两个电路的相对作用，这两个电路编码定位声音所需的线索，并生成将头部、眼睛和耳朵定位到声学目标的运动程序。其中一个回路涉及下丘和上丘的中脑核团，上丘深层向脑干的运动回路输出信号。另一个环路涉及从下丘到内侧膝状体和初级听觉皮质的投射。通过使大脑皮层或中脑失活，这两个回路在定向行为中的相对作用将被确定。第二个目的是通过测试前庭系统中半规管失活后的反射来检查前庭-耳部反射。我们将堵塞半规管，并假设这将极大地减弱反射。在有活动耳廓的动物中，假设反射用于稳定听觉世界，就像前庭-眼睛反射在头部运动时稳定视网膜上的图像一样。最终目标是将推动耳廓运动的电路作为模型马达系统进行研究，并将其与众所周知的动眼神经电路进行比较。我们还将研究固定耳廓对声音定位性能的影响。

DESCRIPTION (provided by applicant): The overall aim of this project is to understand the neural mechanisms of sound localization. These results will help us understand how the brain integrates auditory information from the two ears and produces orienting movements of the head, eyes, and ears to allow close visual and auditory inspection of targets. The experiments are designed to test the relative roles of two circuits that arise in the auditory brainstem to encode the cues necessary to localize sounds and generate the motor programs that orient the head, eyes and ears to the acoustic target. One circuit involves the midbrain nuclei of the inferior and superior colliculi with outputs to motor circuits in the brainstem from the deep layers of the superior colliculus. The other circuit involves projections from the inferior colliculus to the medial geniculate and primary auditory cortex. By inactivating the cortex or the midbrain, the relative roles of these two circuits in orienting behavior will be determined. The second aim will examine the vestibulo-auricular reflex by testing for the reflex following inactivation of the semicircular canals in the vestibular system. We will plug the semicircular canals and hypothesize that this will greatly attenuate the reflex. In animals with mobile pinnae, it is hypothesized that the reflex serves to stabilize the auditory world just like the vestibulo-ocular reflex stabilizes images on the retina in the presence of head movements. The final aim will study the circuitry that moves the pinna as a model motor system and compare it with the well-known oculomotor circuit. We will also examine the effect of immobilizing the pinna on sound localization performance.