Synergistic in vivo and in vitro approaches in the MSO

描述（由申请人提供）：内侧上橄榄（MSO）的主要神经元处理耳间时差（ITDs），用于沿水平面定位声音的线索，以及在噪声中检测语音和通信信号。尽管人们对理解过渡段加工背后的电路动力学有着浓厚的兴趣，但令人惊讶的是，很少有实验数据可用于驱动双耳听力和MSO功能的当前模型。这部分是由于生物物理特化是MSO神经元功能作用的核心，这使得这些神经元异常难以用传统的细胞外记录方法在体内记录。尽管膜片钳在脑切片中记录MSO神经元的出现，使得对MSO神经元突触特性的详细研究成为可能，但电路连接的强制性中断阻碍了这些研究准确地再现双耳输入的生理时间和平衡。目前的提案将提供第一个明确的努力，以弥合体外细胞电生理方法和体内全动物声学研究之间的概念和技术差距。首先，我们将使用膜片钳记录活体MSO神经元对单耳和双耳刺激的反应。我们将使用细胞内方法比较单侧和对侧声刺激的反应，包括时间、形状和(a)对称性。我们将测试这些单耳反应是否允许我们预测同一神经元的双耳反应，我们也将测量。其次，为了解释体内实验，我们将开发一种包含听神经以及整个耳蜗核和上橄榄复合体的切片制剂。通过在MSO神经元的全细胞记录过程中同步刺激一条或两条听神经，我们将在体外重现兴奋性和抑制性突触输入的自然时间，其细节是目前所有MSO双耳加工模型的基础。通过比较对照反应与甘氨酸能抑制药物阻断期间引起的反应，还将探讨抑制的影响和时间。

DESCRIPTION (provided by applicant): The principal neurons of the medial superior olive (MSO) process interaural time differences (ITDs), cues used for localizing sounds along the horizontal plane as well as detection of speech and communication signals in noise. Despite intense interest in understanding the circuit dynamics that underlie ITD processing, there is surprisingly little experimental data available to drive current models of binaural hearing and MSO function. This is in part due to the fact that the biophysical specializations that are central to MSO neurons< functional role make these neurons unusually difficult to record in vivo with traditional extracellular recording methods. Although the advent of patch-clamp recordings from MSO neurons in brain slices has enabled detailed studies of the synaptic properties of MSO neurons, the obligatory disruption of circuit connections has precluded these studies from accurately reproducing the physiological timing and balance of binaural inputs. The current proposal will provide the first explicit effort to bridge the conceptual and technical gaps between cellular electrophysiological approaches in vitro and whole-animal acoustic investigations in vivo. First, we will employ patch-clamp recordings from MSO neurons in vivo and record responses to both monaural and binaural stimuli. We will use intracellular methods to compare the responses to ipsi- and contralateral acoustic stimulation in terms of their timing, shape, and (a) symmetry. We will test whether these monaural responses allow us to predict the binaural responses of the same neurons, which we will also measure. Second, in order to interpret in vivo experiments, we will develop a slice preparation containing the auditory nerve as well as the entire cochlear nucleus and superior olivary complex. By synchronously stimulating one or both auditory nerves during whole-cell recordings from MSO neurons, we will reproduce in vitro the natural timing of excitatory and inhibitory synaptic inputs, the details of which are the basis for all current models of binaural processing in the MSO. The impact and timing of inhibition will also be explored by comparing control responses to those evoked during pharmacological blockade of glycinergic inhibition. PUBLIC HEALTH RELEVANCE: Binaural cues are critical for speech perception and sound localization, and in recent years have become critical components of stimulation paradigms in auditory prostheses. An understanding of how binaural cues are processed by the brain is thus a prerequisite for the development of effective solutions for deafness and other hearing disorders.