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

自我运动诱导了对环境感知的相关变化：在视觉系统中，这种行为和感知之间的密切联系已经得到了广泛的研究，其中线性运动诱导了对视觉流场的感知。视觉流场提供了关于物体之间的空间布局和评估器到这些物体的距离的关键信息。然而，这些信息不仅可以通过视觉获得：回声定位蝙蝠，在完全黑暗的高度混乱的3D环境中飞行，很可能利用回声声流场信息进行导航：以前的工作强调了蝙蝠的特殊能力，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，以重建其环境和物体的3D布局。然而，对空间时空表征的动态变化的感知和神经表征，即蝙蝠在飞行中将经历的回声声流场，在很大程度上是未知的。本研究旨在探讨蝙蝠回声声流场分析的感知能力和神经生理基础。为此，采用了心理物理和电生理相结合的方法：将在最先进的风洞中训练蝙蝠进行线性飞行，并呈现虚拟回声声流场，该流场是通过复杂的时空实时处理和回放蝙蝠在飞行中产生的声纳发射而产生的。与视觉流场研究一样，招募虚拟回声声流场允许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。作为对心理物理研究的补充，我们最近的电生理工作表明，背侧听觉皮层中众所周知的时位排列（即回声延迟的地形表征）与神经元的系统空间调谐共变。这种距离和方位角神经码的共变为回声流场的显式神经码提供了支持。本研究旨在通过先进的刺激和记录技术来评估这一候选神经基质的功能，这些技术首先在麻醉下应用，然后在清醒和有行为的飞行动物中应用。

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.