Department of Mechanical Engineering, Virginia Tech, 1075 Life Science Circle, Blacksburg, Virginia 24061, USA.
J Acoust Soc Am. 2020 Jan;147(1):469. doi: 10.1121/10.0000582.
Many bat species, e.g., in the rhinolophid and hipposiderid families, have dynamic biosonar systems with highly mobile pinnae. Pinna motion patterns have been shown to fall into two distinct categories: rigid rotations and non-rigid motions (i.e., deformations). In the present work, two questions regarding the rigid rotations have been investigated: (i) what is the nature of the variability (e.g., discrete subgroups or continuous variation) within the rigid motions, (ii) what is its acoustic impact? To investigate the first question, rigid pinna motions in Pratt's leaf-nosed bats (Hipposideros pratti) have been tracked with stereo vision and a dense set of landmark points on the pinna surface. Axis-angle representations of the recorded rigid motions have shown a continuous variation in the rotation axes that covered a range of almost 180° in azimuth and elevation. To investigate the second question, the observed range of rigid pinna motions has been reproduced with a biomimetic pinna. Normalized mutual information between acoustic inputs associated with every pair of the rigid pinna motions showed that even small changes in the rotation axis resulted in more than 50% new sensory information encoding capacity (i.e., normalized mutual information less than 50%). This demonstrates a potential sensory benefit to the observed variability in the rigid pinna rotations.
许多蝙蝠物种，例如菊头蝠科和蹄蝠科中的蝙蝠，具有高度灵活的生物声纳系统，其耳郭可以进行动态运动。耳郭运动模式可分为两类：刚性旋转和非刚性运动（即变形）。在本研究中，我们针对刚性旋转提出了两个问题：（i）刚性运动中的可变性（例如离散子组或连续变化）的性质是什么，（ii）它的声学影响是什么？为了研究第一个问题，我们使用立体视觉和在耳郭表面上的密集地标点对叶口蝠（Hipposideros pratti）的刚性耳郭运动进行了跟踪。记录的刚性运动的轴角表示法显示，旋转轴具有连续变化，其在方位角和仰角上的覆盖范围几乎达到 180°。为了研究第二个问题，我们使用仿生耳郭再现了观察到的刚性耳郭运动范围。与每对刚性耳郭运动相关的声学输入之间的归一化互信息表明，即使旋转轴发生很小的变化，也会导致超过 50%的新感觉信息编码能力（即归一化互信息小于 50%）。这表明观察到的刚性耳郭旋转中的可变性具有潜在的感觉益处。
