Modulation of spatial representations within the early auditory pathway by active sensing

在导航环境时定位和识别感官对象是基本的大脑功能。然而，在不受限制的自我运动中，单个物体是如何在神经上被表征的，这在很大程度上是未知的。基于早期由DFG资助的一个项目，我们最近开发了一个新的自由移动实验范式来研究听觉加工和声音感知（感觉岛任务，SIT）。利用SIT，我们观察了初级听觉皮层（A1）中先前未报道的空间声源表征：A1神经元的自我中心角度偏好根据声源的任务特异性身份发生显著变化，揭示了自我运动过程中自然感知的一种新的皮层计算原理。这些深刻的新发现提出了关于潜在回路和机制的基本问题。具体来说，中脑下丘中枢（IC）、丘脑内侧膝状体（MGB）和A1之间的循环连接被认为参与了感觉信息的转换和选择性门控，以形成知觉表征。因此，这个网络是我们已经确定的新空间表征组织的主要候选。因此，为了从机制上理解A1中身份特异性空间调节的发现，我们的目标是研究相同的行为范式如何影响IC和MGB中的空间表征。为此，我们计划在SIT的主动定位和不受限制的自我运动期间长期记录这些大脑区域。受A1中发现的启发，我们将确定空间表征与传统观察到的纯粹以自我为中心的调优在多大程度上不同。此外，利用有针对性的光遗传学操作，我们将剖析A1对IC和MGB的突出反馈在SIT过程中对空间表征的产生以及行为表现的作用。

Localizing and identifying sensory objects while navigating the environment are fundamental brain functions. However, how individual objects are neuronally represented during unrestricted self-motion is mostly unexplored. Based on an earlier project funded by the DFG, we recently developed a new freely moving experimental paradigm to study auditory processing and sound perception (Sensory Island Task, SIT). Using SIT, we observed previously unreported spatial sound-source representations in primary auditory cortex (A1): the egocentric angle preference of A1 neurons changed significantly depending on the task-specific identity of the sound-source, revealing a novel cortical computation principle for naturalistic sensing during self-motion. These profoundly new findings raise fundamental questions about the underlying circuits and mechanisms. Specifically, the recurrent connectivity between the midbrain hub of the Inferior Colliculus (IC), the Medial Geniculate Body (MGB) in the thalamus and A1 has been suggested to be involved in the transformation and selective gating of sensory information to form perceptual representations. It follows that this network is a prime candidate for the organization of the new spatial representations that we have identified. Thus, to gain a mechanistic understanding of our findings of identity-specific spatial tuning in A1, we aim to study how the same behavioral paradigm affect spatial representations in IC and MGB. To this end, we plan to record chronically in these brain regions during active localization and unrestricted self-motion in SIT. Inspired by our findings in A1, we will determine to what extent spatial representations differ from traditionally observed pure egocentric tuning. Moreover, using targeted optogenetic manipulations, we will dissect the role of the prominent feedback of A1 to IC and MGB for the generation of spatial representations during SIT as well as for behavioral performance.