Multisensory competition and spatial selection: Neural circuit and computational mechanisms

项目摘要 动物不断地从刺激丰富的环境中接触到一连串的多感官输入。他们 通过让他们的行为由身体上最突出的(或更多)来指导，来处理这种信息复杂性 一般来说，环境中最重要的)刺激源。最肉体的辨认 显著的刺激是通过刺激竞争的神经机制发生的，而这种竞争必然会起作用 跨越感官形态和空间位置。尽管多感官整合的机制 已被广泛研究，内部和内部竞争的电路和计算原理 跨感觉模式在很大程度上是未知的。最近有关猴子行为的证据表明， 中脑上丘(SC)是正常竞争刺激选择的关键。同时，我们的 最近对谷仓猫头鹰视顶盖(OT，SC的鸟类同源物)的研究揭示了特殊的神经 反应性质，即最强刺激的绝对信号，可以解释SC的 在选择行为中的关键作用。GABA能中脑核--峡部的抑制 巨细胞(IMC)是调节这些反应特性所必需的。尽管如此，计算和 IMC作用于竞争性刺激选择的机制逻辑仍不清楚。在这里，我们 建议系统地解开由IMC-OT网络协调的基础计算 多感官竞争，并将它们的实现明确映射到电路元件上。具体来说，我们首先 目的阐明在存在噪声的情况下，最强刺激的可靠信号是如何传递的，即“稳健”。 信令)被实现。我们的假设是，从IMC到IMC的特殊的甜甜圈状空间抑制模式 加时赛发挥着核心作用。其次，我们的目标是了解IMC是否是一个活跃的计算轨迹 在加时赛中刺激竞争。我们的假设是，IMC内部的竞争性互动控制着 加班分类的准确性和力度。第三，我们问OT如何解决杂乱无章的竞争 包含几种刺激的感官场景。我们的假设是，动态抑制平衡在 多个相互竞争的位置可保护OTid响应不被驱使为零，并允许在整个网络范围内 最强刺激的解码。我们将使用体内电生理学和药物来验证这些假说 清醒、固定头部的谷仓猫头鹰的离子导入和计算模型。在所有情况下，我们将 明确测试假设的竞争机制是否适用于各种感觉通道。 这三个目标的初步数据支持了我们的假设。它们表明，拟议的 实验有能力揭示执行复杂的电路组织的战略原则 为多感官竞争和刺激选择提供支持的计算。

Project Summary Animals are constantly exposed to a barrage of multisensory input from their stimulus-rich environments. They handle this informational complexity by having their behavior guided by the most physically salient (or more generally, the most important) stimulus source in the environment. The identification of the most physically salient stimulus occurs through neural mechanisms of stimulus competition, which must necessarily operate across sensory modalities and across spatial locations. Although the mechanisms of multisensory integration have been studied extensively, the circuit and computational principles underlying competition within and across sensory modalities are largely unknown. Recent evidence from behaving monkeys has revealed the midbrain superior colliculus (SC) as being critical for normal competitive stimulus selection. In parallel, our recent work in the barn owl optic tectum (OT, the avian homolog of the SC) has revealed special neural response properties, namely categorical signaling of the strongest stimulus, that can account for the SC's critical role in selection behavior. Inhibition from a GABAergic midbrain nucleus, the isthmi pars magnocellularis (Imc), is necessary to mediate these response properties. Nonetheless, the computational and mechanistic logic of Imc function in service of competitive stimulus selection remain unknown. Here, we propose to systematically unravel fundamental computations orchestrated by the Imc-OT network for multisensory competition, and to map their implementation explicitly onto circuit elements. Specifically, we first aim to elucidate how the reliable signaling of the strongest stimulus in the presence of noise, i.e, “robust” signaling, is implemented. Our hypothesis is that special donut-like patterns of spatial inhibition from the Imc to the OT play a central role. Second, we aim to understand if the Imc is an active computational locus for stimulus competition in the OT. Our hypothesis is that competitive interactions within the Imc control the accuracy and strength of categorization by the OT. Third, we ask how the OT resolves competition in cluttered sensory scenes that contain several stimuli. Our hypothesis is that a dynamic inhibitory balance among the multiple competing locations protects OTid responses from being driven to zero and permits network wide decoding of the strongest stimulus. We will test the hypotheses using in vivo electrophysiology and drug iontophoresis in awake, head-fixed barn owls together with computational modeling. In all cases, we will explicitly test whether the hypothesized mechanisms of competition generalize across sensory modalities. Preliminary data from the three aims support our hypotheses. They indicate that results from the proposed experiments have the power to reveal strategic principles of circuit organization for executing the sophisticated computations that subserve multisensory competition and stimulus selection.