The Relationship Between Reliance on Food Caching, Spatial Memory and the Hippocampus - An Intraspecific Comparison

储存食物的鸟类依靠它们的食物储藏室过冬，并使用空间记忆成功地恢复食物。理论和经验研究都表明，能量要求高的生态条件应该导致更密集的食物缓存。因此，对空间记忆和海马体提出更高要求的环境条件会导致空间记忆增强，并将研究具有更多神经元的扩大的海马体。一种比较的方法和一个普通的花园实验将被用来检验一个预测，即北方种群中的黑帽山雀进化出了增强的空间记忆和具有更多神经元的扩大的海马体。首先，将比较来自12个种群的黑帽山雀沿纬度梯度的海马体结构。理论模型还表明，随着成功的缓存恢复，更多的缓存应该会显着增加鸟类的存活概率，特别是当环境条件更加耗能和不可预测的时候，比如北部地区的环境条件。因此，由于严酷的冬季条件，生活在更北部环境的山雀应该更多地依赖缓存，因此应该比更南边的同类对空间记忆的要求更高。为了确定北方和南方山雀之间在记忆和海马体上的差异是否已经进化，我们将进行一个共同的花园实验，其中北方和南方黑帽山雀取自巢中并在相同的实验室条件下人工饲养，以检验来自适应性专门化假说的两个预测：(1)北方种群的个体应该具有相对更大的海马区，有更多的神经元和更高的细胞增殖率；(2)北方和南方种群之间的这些差异是由于对记忆和海马体的选择压力更大而进化的，因此他们有遗传基础。研究鸟类的环境、记忆和海马体之间的关系将促进我们对记忆和大脑进化的理解。拟议的活动每年将为1名博士后助理、2-3名本科生和1-2名社区大学实习生提供跨学科研究培训。将尽一切努力从生物科学中代表性不足的群体中招聘这些职位的候选人。研究结果将在国家和国际会议上公布，并在同行评议的期刊上发表。拟议研究的结果和理由将通过免费访问的网站、大众媒体上的出版物、在当地社区大学的演讲和本科生授课等方式向更广泛的受众提供。所有经过处理的脑组织将用于本科生和研究生的教学。这项拟议的研究是跨学科的，它将促进行为生态学、神经生物学和内分泌学领域的整合。

Food-storing birds rely on their food caches to survive winters and use spatial memory for successful food recovery. Both theoretical and empirical studies suggest that energetically demanding ecological conditions should result in more intensive food caching. Thus, environmental conditions that place higher demands on spatial memory and the hippocampus result in enhanced spatial memory and an enlarged hippocampus with more neurons will be investigated. A comparative method and a common garden experiment will be used to test a prediction that black-capped chickadees in northern populations have evolved enhanced spatial memory and an enlarged hippocampus with more neurons. First, hippocampal structure in black-capped chickadees from twelve populations along a latitudinal gradient will be compared. Theoretical models also suggest that more caching along with successful cache recovery should significantly increase the probability of survival in birds specifically when environmental conditions are more energetically demanding and unpredictable like those in northern locations. Therefore chickadees living in more northern environments should depend on caches more heavily because of harsher winter conditions, and thus should experience higher demands for spatial memory than their more southern conspecifics. To determine whether differences in memory and the hippocampus between northern and southern chickadees have evolved, a common garden experiment in which northern and southern black-capped chickadees taken from nests and hand-raised under identical laboratory conditions will be conducted to test two predictions from the adaptive specialization hypothesis: (1) individuals in northern populations should have a relatively larger hippocampus with more neurons and higher cell proliferation rates; and (2) these differences between northern and southern populations have evolved as a result of greater selection pressure on memory and the hippocampus and thus they have a genetic basis. Studying the relationship between environment, memory and the hippocampus in birds will advance our understanding of the evolution of memory and the brain. The proposed activity will provide interdisciplinary research training to one postdoctoral associate, to 2-3 undergraduate students and to 1-2 interns from a community college per year. Every effort will be made to recruit candidates for these positions from underrepresented groups in the biological sciences. The results of the study will be presented at national and international meetings, and published in peer-reviewed journals. Results and rationale of the proposed study will made available to a broader audience through a freely accessible web site, publications in popular media, presentations at local community colleges and through teaching undergraduate classes. All processed brain tissue will be used in teaching undergraduate and graduate students. The proposed study is interdisciplinary and it will bolster integration between the fields of behavioral ecology, neurobiology, and endocrinology.