Gutiérrez-Ibáñez Cristián, Iwaniuk Andrew N, Wylie Douglas R
Department of Psychology, University of Alberta, Edmonton, Canada.
Brain Behav Evol. 2009;74(4):280-94. doi: 10.1159/000270904. Epub 2009 Dec 24.
In vertebrates, sensory specializations are usually correlated with increases in the brain areas associated with that specialization. This correlation is called the 'principle of proper mass' whereby the size of a neural structure is a reflection of the complexity of the behavior that it subserves. In recent years, several comparative studies have revealed examples of this principle in the visual and auditory system of birds, but somatosensory specializations have largely been ignored. Many species rely heavily on tactile information during feeding. Input from the beak, tongue and face, conveyed via the trigeminal, facial, glossopharyngeal and hypoglossal nerves, is first processed in the brain by the principal sensory nucleus of the trigeminal nerve (PrV) in the brainstem. Previous studies report that PrV is enlarged in some species that rely heavily on tactile input when feeding, but no extensive comparative studies have been performed. In this study, we assessed the volume of PrV in 73 species of birds to present a detailed analysis of the relative size variation of PrV using both conventional and phylogenetically based statistics. Overall, our results indicate that three distinct groups of birds have a hypertrophied PrV: waterfowl (Anseriformes), beak-probing shorebirds (Charadriiformes), and parrots (Psittaciformes). These three groups have different sensory requirements from the orofacial region. For example, beak-probing shorebirds use pressure information from the tip of the beak to find buried prey in soft substrates, whereas waterfowl, especially filter-feeding ducks, use information from the beak, palate, and tongue when feeding. Parrots likely require increased sensitivity in the tongue to manipulate food items. Thus, despite all sharing an enlarged PrV and feeding behaviors dependent on tactile input, each group has different requirements that have led to the independent evolution of a large PrV.
在脊椎动物中，感觉特化通常与该特化相关的脑区增加有关。这种相关性被称为“适当质量原则”，即神经结构的大小反映了它所服务行为的复杂性。近年来，一些比较研究揭示了鸟类视觉和听觉系统中这一原则的实例，但躯体感觉特化在很大程度上被忽视了。许多物种在进食时严重依赖触觉信息。来自喙、舌头和面部的输入，通过三叉神经、面神经、舌咽神经和舌下神经传递，首先在脑干中的三叉神经主感觉核（PrV）中进行脑内处理。先前的研究报告称，在一些进食时严重依赖触觉输入的物种中，PrV会增大，但尚未进行广泛的比较研究。在本研究中，我们评估了73种鸟类的PrV体积，使用传统统计方法和基于系统发育的统计方法对PrV的相对大小变化进行了详细分析。总体而言，我们的结果表明，有三类不同的鸟类具有肥大的PrV：水禽（雁形目）、用喙探测的滨鸟（鸻形目）和鹦鹉（鹦形目）。这三类鸟对面部区域有不同的感觉需求。例如，用喙探测的滨鸟利用来自喙尖的压力信息在软质基质中寻找埋藏的猎物，而水禽，尤其是滤食性鸭子，在进食时利用来自喙、上颚和舌头的信息。鹦鹉可能需要舌头有更高的敏感度来操控食物。因此，尽管这三类鸟都有增大的PrV且进食行为都依赖触觉输入，但每一类都有不同的需求，导致了PrV的独立进化。
