Echolocation on the wing: perception and neural representation of echo-acoustic flow fields in bats

自我运动导致环境感知的相关变化：动作和感知之间的这种密切联系在视觉系统中得到了广泛的研究，其中线性运动诱导视觉流场的感知。视觉流动场提供了关于物体之间的空间布局和评估者到这些物体的距离的关键信息。然而，这种信息不仅可以通过视觉获得：回声定位蝙蝠，在高度杂乱的3D环境中完全黑暗中飞行，很可能利用回声声场信息进行导航：以前的工作突出了蝙蝠的非凡能力，以及潜在的神经过程，从返回的回声中提取空间和时间信息，以重建其环境和内部物体的3D布局。然而，蝙蝠在飞行中将经历的回声声场的时空动态变化的感知和神经表征在很大程度上是未知的。本研究旨在探讨蝙蝠回声声场分析的感知能力和神经生理学基础。为此，采用了心理物理和电生理相结合的方法：蝙蝠将在最先进的风洞中接受直线飞行训练，并呈现虚拟回声声场，通过对飞行中蝙蝠产生的声纳发射进行复杂的时空实时处理和回放而产生。就像在视觉流场研究中一样，招募虚拟回声声场可以对流场信息进行详细的、假设驱动的操作，并对蝙蝠对这些操作的感知敏感性进行正式的心理物理评估。作为心理物理研究的补充，我们最近的电生理学工作表明，众所周知的背侧听觉皮质的时间安排(即回声延迟的地形图表示)与神经元的系统空间调谐有关。距离和方位的神经代码的这种共同变化支持用于回声声场的显式神经代码。这项建议旨在通过先进的刺激和记录技术来评估这种候选神经基质的功能，首先在麻醉下应用，然后在飞行中清醒和行为的动物身上应用。

Self motion induces correlated changes in the percept of our environment: This close link between action and perception has been extensively studied in the visual system, where linear motion induces the percept of a visual flow field. Visual flow-fields provide crucial information both about the spatial layout between objects and the distance of the assessor to these objects. However, this information can not only be gained visually: Echolocating bats, flying in complete darkness through highly cluttered 3D environments, are very likely to exploit echo-acoustic flow-field information for navigation: Previous work has highlighted the exceptional capabilities of bats, and underlying neural processes, to extract both spatial and temporal information from returning echoes for reconstructing 3D layouts of their environment and objects within. Perception and neural representation of the dynamical changes of spatio-temporal representation of space, i.e., the echo-acoustic flow field a bat will experience in flight are, however, largely unknown.This proposal aims to investigate the perceptual capabilities and neurophysiological basis of echo-acoustic flow-field analysis in bats. To this aim a combined psychophysical and electrophysiological approach is used: Bats will be trained on linear flight in a state-of-the-art wind tunnel and presented with virtual echo-acoustic flow fields, generated through complex spatio-temporal real-time processing and playback of sonar emissions produced by the bats in flight. As in visual flow-field research, recruiting virtual echo-acoustic flow fields allows for detailed, hypothesis-driven manipulation of the flow-field information and formal psychophysical assessment of the perceptual sensitivity of the bats to these manipulations.Complementing the psychophysical research, our recent electrophysiological work has shown that the well-known chronotopic arrangement in dorsal auditory cortex (i.e., the topographic representation of echo delay) co-varies with a systematic spatial tuning of the neurons. This co variation of the neural code for distance and azimuth supports an explicit neural code for echo acoustic flow fields. This proposal aims to evaluate the function of this candidate neural substrate with advanced stimulation- and recording techniques, applied first under anesthesia and subsequently in the awake and behaving animal in flight.