Iwaniuk A N, Pellis S M, Whishaw I Q
Department of Psychology and Neuroscience, University of Lethbridge, Lethbridge, Alta., Canada.
Brain Behav Evol. 1999 Sep;54(3):167-80. doi: 10.1159/000006621.
To test the hypothesis that brain size and forelimb dexterity are positively correlated, the relative brain size of 41 species of fissiped (terrestrial) carnivores (Order: Carnivora) was examined with respect to their forelimb use during feeding. With the use of a newly derived dexterity index, the forelimb dexterity executed by each of the species was calculated as a single, continuous variable which was then regressed against the residuals of brain size. To account for confounding effects of phylogenetic inertia, the analysis was performed with independent contrasts analysis using a speciational model of evolutionary change (i.e. equal branch lengths). The results suggest that relative brain size and isocortex size are not correlated with the dexterity of the proximal or distal segments or a combination of the two (total forelimb dexterity). The presence of species with widely different brain sizes and similar dexterities, and vice versa, suggests that an increase in the amount of neural substrate might not be necessary for the production of finely coordinated forelimb movements. It is suggested that this outcome is representative of the plasticity of both mammalian brain size and behavior and that variations in brain size and forelimb dexterity could be linked to disparate ecological and phylogenetic factors which act in concert to promote or constrain neural development and behavior in different species.
为了验证大脑大小与前肢灵活性呈正相关这一假设，研究人员考察了41种裂脚（陆生）食肉动物（食肉目）的相对大脑大小与它们在进食时前肢使用情况的关系。利用新得出的灵活性指数，将每个物种的前肢灵活性计算为一个单一的连续变量，然后将其与大脑大小的残差进行回归分析。为了考虑系统发育惯性的混杂效应，采用基于进化变化的物种形成模型（即等分支长度）的独立对比分析进行分析。结果表明，相对大脑大小和同型皮质大小与近端或远端节段的灵活性或两者的组合（前肢总灵活性）无关。存在大脑大小差异很大但灵活性相似的物种，反之亦然，这表明产生精细协调的前肢运动可能不需要增加神经基质的数量。有人认为，这一结果代表了哺乳动物大脑大小和行为的可塑性，大脑大小和前肢灵活性的变化可能与不同的生态和系统发育因素有关，这些因素共同作用，促进或限制不同物种的神经发育和行为。
