Mechanisms of sound localization investigated with head-related transfer functions

声音定位行为是人类和动物的一种重要的定向反应，用于固定感兴趣的物体。仓鸮是声音定位的典范系统，因为它占据了夜间生态位。这导致了适应，使仓鸮主要通过倾听来捕猎。通过对仓鸮的研究，我们发现了声音定位的许多机制。到目前为止，实验方法都是使用单一刺激参数。实验表明，耳间时差对方位声定位起主要作用，而耳间声级差对高度声定位起重要作用。然而，这些实验也进一步表明，迄今为止未知的线索影响声音定位行为和提取声音定位信息的神经元的反应。目前还不清楚是否以及如何消除具有相同宽频间时间和电平差异的空间位置的歧义。为了解决这些问题，我们提出了一种新的方法，使用头部相关传递函数（hrtf）进行刺激。在鼓膜上录制的HRTF包含了来自空间中一个位置的信息，尽管被听者的身体、头部和外耳扭曲了。因此，hrtf应该包含听者在声音定位中可以使用的最完整的信息。我们提出理论与实验的密切互动，分五个步骤进行：1)记录HRTF； 2)分析HRTF，通过反向建模，找出HRTF记录的位置是否可以重建；3)在行为实验中使用正常和操纵的HRTF刺激，找出HRTF中包含的哪些信息被动物利用以及如何被利用；4)在电生理记录中使用HRTF刺激，找出哪些信息驱动了尖峰反应。5)使用尖峰响应来尝试重建引起给定响应的源的位置。我们期望新的程序和结果将大大提高我们对声音定位的理解，不仅在仓鸮，而且在其他动物，包括人类。我们的研究也可能产生可以在声音定位系统中实施的结果，如自主代理。

Sound-localization behavior is an important orienting reaction of humans and animals that serves to fixate interesting objects. The barn owl is a model system for sound localization because of the nocturnal ecological niche it occupies. This led to adaptations that allow the barn owl to hunt mainly by listening. Many mechanisms underlying sound localization have been worked out through work in the barn owl. So far experimental approaches have used single stimulus parameters. Such experiments showed that the interaural time difference plays the main role in azimuthal sound localization, while the interaural level difference is important for elevational sound localization. However, these experiments have also suggested that further, hitherto unknown cues influence sound-localization behavior and the responses of neurons extracting sound-localization information. It specifically remains unclear whether and how positions in space may be disambiguated that have equal broadband interaural time and level differences. To tackle such questions we propose a new approach, using head-related transfer functions (HRTFs) for stimulation. The HRTF recorded at the eardrum contains the information originating from one position in space, albeit distorted by the body, head, and the outer-ear of the listener. HRTFs should, thus, contain the most complete information a listener can use in sound localization. We propose a close interaction of theory and experiment, proceeding in five steps: 1) record HRTFs, 2) analyze the HRTFs and find out whether the position where the HRTF was recorded can be reconstructed by reverse modelling, 3) use normal and manipulated HRTF-stimuli in behavioral experiments to find out which information contained in the HRTF is used by the animal and how, 4) use HRTF-stimuli in electrophysiological recordings to find out which information drives the spiking responses, and 5) use the spiking responses to try to reconstruct the position of the source that elicited a given response. We expect that the new procedures and results will significantly advance our understanding of sound localization, not only in the barn owl, but also in other animals, including humans. Our studies may also yield results that may be implemented in sound-localizing systems, like autonomic agents.