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

点击翻译按钮获取中文摘要

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.