Gould Kristy L, Gilbertson Karl E, Hrvol Andrew J, Nelson Joseph C, Seyfer Abigail L, Brantner Rose M, Kamil Alan C
Department of Psychology, Luther College, Decorah, IA 52101, USA.
Brain Behav Evol. 2013;81(1):56-70. doi: 10.1159/000345560. Epub 2013 Jan 29.
The relative size of the avian hippocampus (Hp) has been shown to be related to spatial memory and food storing in two avian families, the parids and corvids. Basil et al. [Brain Behav Evol 1996;47:156-164] examined North American food-storing birds in the corvid family and found that Clark's nutcrackers had a larger relative Hp than pinyon jays and Western scrub jays. These results correlated with the nutcracker's better performance on most spatial memory tasks and their strong reliance on stored food in the wild. However, Pravosudov and de Kort [Brain Behav Evol 2006;67:1-9] raised questions about the methodology used in the 1996 study, specifically the use of paraffin as an embedding material and recalculation for shrinkage. Therefore, we measured relative Hp volume using gelatin as the embedding material in four North American species of food-storing corvids (Clark's nutcrackers, pinyon jays, Western scrub jays and blue jays) and one Eurasian corvid that stores little to no food (azure-winged magpies). Although there was a significant overall effect of species on relative Hp volume among the five species, subsequent tests found only one pairwise difference, blue jays having a larger Hp than the azure-winged magpies. We also examined the relative size of the septum in the five species. Although Shiflett et al. [J Neurobiol 2002;51:215-222] found a difference in relative septum volume amongst three species of parids that correlated with storing food, we did not find significant differences amongst the five species in relative septum. Finally, we calculated the number of neurons in the Hp relative to body mass in the five species and found statistically significant differences, some of which are in accord with the adaptive specialization hypothesis and some are not.
鸟类海马体（Hp）的相对大小已被证明与两个鸟类家族（山雀科和鸦科）的空间记忆及食物储存有关。巴西尔等人[《大脑行为与进化》1996年；47:156 - 164]研究了北美鸦科中储存食物的鸟类，发现克拉克胡桃夹的Hp相对大小比松鸦和西部灌丛鸦更大。这些结果与胡桃夹在大多数空间记忆任务中的更好表现以及它们在野外对储存食物的强烈依赖相关。然而，普拉沃苏多夫和德科特[《大脑行为与进化》2006年；67:1 - 9]对1996年研究中使用的方法提出了疑问，特别是使用石蜡作为包埋材料以及对收缩进行重新计算的问题。因此，我们使用明胶作为包埋材料，测量了四种北美储存食物的鸦科鸟类（克拉克胡桃夹、松鸦、西部灌丛鸦和蓝鸦）以及一种几乎不储存食物的欧亚鸦科鸟类（蓝翅喜鹊）的Hp相对体积。尽管在这五个物种中，物种对Hp相对体积有显著的总体影响，但后续测试仅发现了一对差异，即蓝鸦的Hp比蓝翅喜鹊更大。我们还研究了这五个物种中隔膜的相对大小。尽管希夫利特等人[《神经生物学杂志》2002年；51:215 - 222]发现三种山雀科物种的隔膜相对体积存在差异，且与食物储存相关，但我们在这五个物种的隔膜相对大小上未发现显著差异。最后我们计算了这五个物种中Hp相对于体重的神经元数量，发现了具有统计学意义的差异，其中一些符合适应性特化假说，而一些则不符合。
