Eyes over ears? Bats as neuroethological models for understanding visual capture

我们如何感知世界取决于我们的感官所能获得的环境信息，以及我们的大脑将由此产生的神经信息整合成统一体验的能力。我的长期目标是更好地理解动物——脊椎动物和无脊椎动物——如何利用感官信息来构建它们经常变化的外部环境的内部表征。在这项为期5年的研究经费中，我将使用蝙蝠来研究它们和其他脊椎动物，包括我们自己，是如何结合视觉和听觉信息来构建我们周围物体空间排列的表征。这种表征对于方向和物体识别很重要，并用于决定吃什么，避免什么，向谁求爱以及如何回家。在所有感官中，视觉和听觉在大脑表达通过它们收集到的信息的方式上有最多的共同点和最大的相似性。出于同样的原因，如果视觉和听觉信息相互矛盾，就有可能产生混淆，特别是当大脑不能迅速决定哪个是更准确、更可靠的信息来源时。对于许多鸟类和哺乳动物来说，当听觉和视觉信息不一致时，大脑往往会选择视觉信息而不是听觉信息来定位物体。有人提出了几种解释，但并不相互排斥。其一是历史原因——因为在脊椎动物的进化过程中，视觉先于听觉，视觉对听觉进化的影响要大于听觉对视觉的影响。第二个是发展性的——这表明随着大脑的发展，视觉系统对听觉系统如何构建外部世界的图像产生了不成比例的影响。第三种假设是，大脑对可用的视觉和听觉信息的相对价值进行实时估计。最后一种解释表明，视觉优势在很大程度上是由于在很多时候，对许多动物来说，可见光比可听到的声音更可靠。以蝙蝠为研究对象来验证这些不同的假设是我研究计划的重点。蝙蝠已经进化到可以在黑夜的掩护下行动。今天的大多数物种，通过对听觉和声音系统的非凡适应，能够用耳朵“看”东西。由于喉部的回声定位，蝙蝠可以做一些没有回声定位的动物不能用声音做的事情：根据它们叫声的回声，它们可以准确地确定物体的距离，以及它的大小、形状和质地。蝙蝠并不是盲人，但由于许多物种更多地依靠回声而不是光来确定方向，蝙蝠提供了一个绝佳的机会来研究哺乳动物的大脑如何构建视觉和听觉图像，以及进化、发展和当前的环境条件如何影响哺乳动物在面对相互矛盾的信息时决定依赖哪种感觉。进化、发展和当前条件都必须对脊椎动物如何优先考虑和整合视听信息施加影响。我将进行行为学、比较学和神经解剖学的研究来理清它们的作用。我还设计了一些实验，看看一些蝙蝠是否有跨模态识别的能力。那就是蝙蝠通过回声定位来感知图像是否与通过视觉感知的图像相似？为了实现这些短期目标，我的研究将增加我们对动物如何建立对周围世界的连贯的内部表征的理解。最终，这些结果可能有助于我们更好地理解自闭症谱系和精神分裂症的各个方面，这些疾病与整合感觉信息的困难有关。

How we perceive the world depends on the environmental information available to our senses and our brain’s ability to integrate the resulting neural information into a unified experience. My long-term objective is better understand how animals - vertebrates and invertebrates alike - use sensory information to construct internal representations of their often changing external environments. Over the course of this 5-year research grant, I will use bats to investigate how they and other vertebrates, including ourselves, combine visual and auditory information to build representations of the spatial arrangements of objects in our surroundings. Such representations are important for orientation and object recognition and are used to make decisions about what to eat, what to avoid, who to court, and how to get home. Among the senses, vision and hearing have most in common and the greatest potential for similarity in the way the brain represents the information gathered through them. For this same reason, if visual and auditory information are contradictory there is potential for confusion, especially if the brain cannot quickly decide which is the more accurate and reliable source. For many birds and mammals, when auditory and visual information do not agree, the brain often chooses visual over auditory information to localize objects. Several explanations, none mutually exclusive, have been suggested to account for this. One is historical – because vision precedes hearing in the evolution of vertebrates, vision has had a greater impact on the evolution of hearing than hearing has had on vision. A second is developmental – suggesting that as the brain develops the visual system has a disproportionate influence on how the auditory system builds images of the outside world. A third postulates that the brain makes real-time estimations on the relative value of available visual and auditory information. This last explanation implies that visual dominance largely results because for much of the time for many animals visible light is more reliable than audible sound. Testing these different hypotheses using bats as subjects is the focus of my research proposal. Bats have evolved to operate under the cover of night. The majority of today’s species, through extraordinary adaptations to their auditory and vocal systems, are able to ‘see’ with their ears. As a result of laryngeal echolocation, bats can do things that non-echolocating animals cannot do using sound: based on the echoes from their calls they can accurately determine an object’s distance and also its size, shape, and texture. Bats are not blind, but because many species rely more on echoes than light for orientation, bats provide an excellent opportunity to study how the mammalian brain builds visual and auditory images and how evolution, development, and current environmental conditions each impact how mammals, faced with conflicting information, decide which sense to rely on. Evolution, development, and current conditions must all exert an influence on how vertebrates prioritize and integrate audio-visual information. I will conduct behavioural, comparative, and neuroanatomical studies to disentangle their roles. I have also designed experiments to see if some bats are capable of cross-modal recognition. That is do bats perceive through echolocation images similar to those perceived through vision? In meeting these short-term objectives, my research will add to our understanding of how animals build coherent internal representations of the world around them. Ultimately, the results may help us to better comprehend aspects of the autism spectrum and schizophrenia, disorders associated with difficulties in integrating sensory information.