Grothe Benedikt, Pecka Michael
Division of Neurobiology, Department of Biology II, Ludwig Maximilians University Munich Munich, Germany.
Front Neural Circuits. 2014 Oct 1;8:116. doi: 10.3389/fncir.2014.00116. eCollection 2014.
Our concepts of sound localization in the vertebrate brain are widely based on the general assumption that both the ability to detect air-borne sounds and the neuronal processing are homologous in archosaurs (present day crocodiles and birds) and mammals. Yet studies repeatedly report conflicting results on the neuronal circuits and mechanisms, in particular the role of inhibition, as well as the coding strategies between avian and mammalian model systems. Here we argue that mammalian and avian phylogeny of spatial hearing is characterized by a convergent evolution of hearing air-borne sounds rather than by homology. In particular, the different evolutionary origins of tympanic ears and the different availability of binaural cues in early mammals and archosaurs imposed distinct constraints on the respective binaural processing mechanisms. The role of synaptic inhibition in generating binaural spatial sensitivity in mammals is highlighted, as it reveals a unifying principle of mammalian circuit design for encoding sound position. Together, we combine evolutionary, anatomical and physiological arguments for making a clear distinction between mammalian processing mechanisms and coding strategies and those of archosaurs. We emphasize that a consideration of the convergent nature of neuronal mechanisms will significantly increase the explanatory power of studies of spatial processing in both mammals and birds.
即检测空气传播声音的能力以及神经元处理过程在主龙类（现代鳄鱼和鸟类）和哺乳动物中是同源的。然而，研究反复报告了在神经元回路和机制方面相互矛盾的结果，特别是抑制作用的作用，以及鸟类和哺乳动物模型系统之间的编码策略。在这里，我们认为，哺乳动物和鸟类空间听觉的系统发育特征是对空气传播声音的听觉趋同进化，而非同源。特别是，鼓膜耳的不同进化起源以及早期哺乳动物和主龙类中双耳线索的不同可用性，对各自的双耳处理机制施加了不同的限制。突触抑制在哺乳动物产生双耳空间敏感性中的作用得到了强调，因为它揭示了哺乳动物用于编码声音位置的回路设计的统一原则。我们综合了进化、解剖学和生理学方面的论据，以明确区分哺乳动物和主龙类的处理机制及编码策略。我们强调，考虑神经元机制的趋同性质将显著提高对哺乳动物和鸟类空间处理研究的解释力。
