Environmental Influences on Spatial Memory and the Hippocampus in Food-Caching Chickadees
Environmental Influences on Spatial Memory and the Hippocampus in Food-Caching Chickadees
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DOI：
10.3819/ccbr.2014.100002
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发表时间：
2015
影响因子：
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通讯作者：
V. Pravosudov;T. Roth;Lara D. LaDage;C. Freas
中科院分区：
文献类型：
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作者：
V. Pravosudov;T. Roth;Lara D. LaDage;C. Freas
认知能力被广泛认为是抵御环境恶劣和不稳定的缓冲器，更好的认知能力对于在恶劣和不可预测的环境中的适应性尤为重要。虽然大脑被认为是高度可塑性和对环境变化的反应，这种环境诱导的可塑性的程度和自然选择的相对贡献，在物种内和物种之间的认知能力和大脑形态的经常大的变化仍然知之甚少。食物缓存山雀提出了一个很好的模型来解决这些问题，因为它们：（一）发生在一个大梯度的环境恶劣，主要取决于冬季气候的严重程度，（B）依赖于食物缓存生存的冬天和他们的能力，检索食物缓存是，至少部分依赖于校园依赖的空间记忆，（c）定期经历一个独特的季节性周期的食物缓存和缓存检索。在这里，我们回顾了一个机构的工作，比较和实验，对两种食物缓存山雀，并讨论这些数据如何与我们的理解环境诱导的可塑性和自然选择如何产生环境相关的变化，在空间记忆和海马体，无论是跨人群，以及跨季节在同一人群。我们认为，现有的证据表明，环境诱导的结构海马可塑性的基础人口变化的作用相对有限。与此同时，由于冬季气候严重程度的差异，以及与空间记忆和海马体中可遗传的个体差异有关，证据与自然选择的历史是一致的。海马形态的季节性变化和食物缓存需求的季节性变化之间似乎没有明确的直接联系。最后，我们建议，海马可塑性与圈养鸟类的实验研究应谨慎看待，因为圈养与许多海马性状，包括体积和在某些情况下神经发生率，但不是神经元数量的大幅减少。另一方面，使用圈养鸟类进行的比较研究似乎提供了更可靠的结果，因为圈养似乎并没有超越种群差异，特别是在海马神经元的数量方面。
Cognitive abilities have been widely considered as a buffer against environmental harshness and instability, with better cognitive abilities being especially crucial for fitness in harsh and unpredictable environments. Although the brain is considered to be highly plastic and responsive to changes in the environment, the extent of such environment-induced plasticity and the relative contributions of natural selection to the frequently large variation in cognitive abilities and brain morphology both within and between species remain poorly understood. Food-caching chickadees present a good model to tackle these questions because they: (a) occur over a large gradient of environmental harshness largely determined by winter climate severity, (b) depend on food caches to survive winter and their ability to retrieve food caches is, at least in part, reliant on hippocampus-dependent spatial memory, and (c) regularly experience a distinct seasonal cycle of food caching and cache retrieval. Here we review a body of work, both comparative and experimental, on two species of food-caching chickadees and discuss how these data relate to our understanding of how environment-induced plasticity and natural selection generate environment-related variation in spatial memory and the hippocampus, both across populations as well as across seasons within the same population. We argue that available evidence suggests a relatively limited role of environmentinduced structural hippocampal plasticity underlying population variation. At the same time, evidence is consistent with the history of natural selection due to differences in winter climate severity and associated with heritable individual variation in spatial memory and the hippocampus. There appears to be no clear direct association between seasonal variation in hippocampus morphology and seasonal variation in demands of food caching. Finally, we suggest that experimental studies of hippocampal plasticity with captive birds should be viewed with some caution because captivity is associated with large reductions in many hippocampal traits, including volume and in some cases neurogenesis rates, but not neuron number. Comparative studies using captive birds, on the other hand, appear to provide more reliable results, as captivity does not appear to override population differences, especially in the number of hippocampal neurons.