Degrees of relevance? The neuronal representation of sound sources in primary auditory cortex during active localization

我们如何在人群中倾听特定的谈话者，或者在交通繁忙的情况下定位一辆车？在日常生活中，多个声源经常同时活跃，但我们的大脑根据来源将这些声音混合成不同的信息流。尽管几十年的研究，这种现象的神经机制的功能理解，这是所谓的听觉场景分析（阿萨），仍然难以捉摸。迄今为止，大多数关于阿萨的研究都集中在被动（即行为无关）设置和以头部为中心（自我中心）的参考框架中对简单声音的即时处理。然而，在现实阿萨期间，存在对感觉输入的连续调制。特别地，由于头部和声源之间的相对角度由于自运动而不断变化，所以声源位置的自我中心编码是不充分的。相反，空间中的绝对（非同心）声源位置的表示将是有益的。此外，阿萨的基本特征是选择性地收听感兴趣的特定声源，这表明声源的编码同样取决于其目标特定的relevances. Consequently，本项目的总体目标是揭示神经元的处理和表示的声源位置在主动导航及其依赖行为的相关性。为此，我开发了一个阿萨范式与多个声源，其中自由移动的啮齿动物执行选择性的听力和定位。本研究利用初级听觉皮层的无线慢性记录，在此范式下研究：1）确定主动导航过程中空间表征的性质; 2）解读A1空间表征在情境空间相关学习过程中的演变; 3）评估行为相关声音定位线索的自我中心表征的情境依赖性。

How do we listen to specific talkers within a crowd or localize an individual car in heavy traffic? In everyday life, multiple sound sources are often simultaneously active, yet our brain unravels this mix of sounds into distinct information streams according to the sources of origin. Despite decades of research, a functional understanding of the neuronal mechanisms of this phenomenon, which is termed auditory scene analysis (ASA), remains elusive. Most studies on ASA to date focused on the instant processing of simple sounds in passive (i.e. behaviorally irrelevant) settings and a head-centered (egocentric) reference frame. However, during realistic ASA, there is a continuous modulation of the sensory input. Particularly, since the relative angle between the head and the sound source is constantly changing due to self-motion, a egocentric coding of sound source positions is inadequate. Rather, a representation of absolute (allocentric) sound source location in space would be beneficial. Moreover, ASA is fundamentally characterized by the selective listening to a particular sound source of interest, suggesting that the coding of a sound source likewise depends on its goal-specific relevance.Accordingly, the overall goal of this project is to reveal the neuronal processing and representation of sound source locations during active navigation and its dependency on behavioral relevance. To this end, I developed an ASA paradigm with multiple sound sources, in which freely moving rodents perform selective listening and localization. Using wireless chronic recordings in primary auditory cortex during task performance in this paradigm, I aim to: 1) Determine the nature of spatial representation during active navigation2) Decipher how spatial representations in A1 evolve during the learning of context-specific spatial relevance3) Assess the context-dependency of egocentric representations of behaviourally relevant sound localization cues.