Constructing auditory space: modulation of the spatial map by auditory cues and landmarks

在环境中寻找路径和导航是生存的关键。50多年的研究表明，为了建立和更新自我在世界上的位置，大脑同时使用外部（非中心）和内部（独特）信息流。因此，当前导航神经科学的中心目标是了解感觉模式如何影响内部空间表征并与之相互作用。为此，研究人员主要操纵视觉、触觉（墙壁、边界）和/或嗅觉感官信息。听觉线索对我们在环境中的定位有很大的帮助。然而，令人惊讶的是，据报道，听觉信息不能或只能对环境中的定向产生不良影响，而听觉模态与独特地图的相互作用或多或少被忽视了。具体而言，听觉线索和习得的音频空间关联在多大程度上以及如何塑造内部空间表征尚未得到很好的研究。感觉岛任务是一种经过充分验证的实验范式，用于探索自由导航啮齿动物的听觉感知。SIT很容易测试声源在多大程度上被用作寻路的空间相关线索，并调查特定声音与固定空间位置之间的局部音频-空间关联的形成。此外，SIT允许在绝对黑暗中觅食，使得空间方向仅依赖于听觉线索和独特信号。因此，它使我们能够引入听觉空间参考框架和由独特路径积分器维护的空间地图之间的冲突。为了了解听觉空间的构建及其对空间表征的影响，我们在听觉空间SIT任务中对自由行为动物的海马区CA1 （HPC CA1，位置细胞）和脾后皮层（RSC，头部方向细胞）进行了慢性记录。由于RSC是整合不同类型的独特和非中心信息（包括地标信息和奖励位置）的枢纽，我们还试图找到与空间相关的听觉地标的神经相关性，例如声源位置的方向或距离调整。此外，由于空间关联随着学习而发展，我们将改变先前获得的任务经验的程度，以测试音频-空间关联建立的速度有多快，以及它在多大程度上影响其空间调制的强度。最后，海马体和RSC的同步电生理记录将允许研究听觉空间对位置细胞和头部方向系统影响的一致性。总之，这个项目将深入了解基于听觉的寻路和空间表征的机制。

Pathfinding and navigation through one’s environment are crucial for survival. Research over 50 years identified that in order to build and update the location of self in the world both external (allocentric) and internal (idiothetic) information streams are used by the brain. Accordingly, a current central goal of navigational neuroscience is to understand how sensory modalities influence and interact with the internal spatial representation. To this end, researchers have manipulated mainly visual, tactile (walls, borders) and/or olfactory sensory information. Auditory cues are highly informative for our orientation in the environment. Yet surprisingly, it has been reported that auditory information can not or only poorly influence orientation in the environment, and the interactions of the auditory modality with idiothetic maps has been more or less overlooked. Specifically, to what extent and how auditory cues and learned audio-spatial associations shape the internal spatial representation is not well investigated. The Sensory-Island Task is a well-tested experimental paradigm for probing auditory perception in freely navigating rodents. SIT readily allows testing to what extent sound sources are used as spatially-relevant cues for pathfinding and to investigate the formation of local audio-spatial associations between a particular sound with a fixed spatial location. Moreover, SIT enables foraging in absolute darkness, rendering the spatial orientation dependent on auditory cues and idiothetic signals only. Thus, it enables us to introduce a conflict between the auditory spatial reference frame and the spatial map maintained by an idiothetic path integrator. To gain understanding over the construction of the auditory space and its influence on the spatial representation we perform chronic recordings from the hippocampal area CA1 (HPC CA1, place cells) and the retrosplenial cortex (RSC, head direction cells) in freely-behaving animals in the audio-spatial SIT task. As RSC serves as a hub integrating different types of idiothetic and allocentric information including landmark information and reward location, we also seek to find neural correlates of spatially-relevant auditory landmarks, exemplified by direction or distance tuning to the location of the sound source. In addition, as spatial associations develop with learning, we will vary the degree of prior gained task experience to test how fast the audio-spatial associations can be established and to what extent it affects the strength of its spatial modulation. Finally, simultaneous electrophysiological recordings in the hippocampus and RSC would allow to investigate the coherence of the influence of the auditory space on both place cell and head direction systems. Together, this project will provide insight into the mechanisms of auditory-based pathfinding and spatial representations.