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贮藏来度过冬天，并利用空间记忆成功地恢复食物。 理论和实证研究都表明，对能量要求很高的生态条件应该导致更密集的食物储藏。 因此，将研究对空间记忆和海马体提出更高要求的环境条件导致增强的空间记忆和具有更多神经元的扩大的海马体。 一种比较方法和一个共同的花园实验将被用来测试一个预测，即北方种群的黑顶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，将比较沿着纬度梯度分布的12个种群的黑帽山雀的海马结构。 理论模型还表明，更多的缓存沿着与成功的缓存恢复应显着增加鸟类的生存概率，特别是当环境条件是更积极的要求和不可预测的，如那些在北方的位置。 因此，生活在北方环境中的山雀应该更严重地依赖缓存，因为更严酷的冬季条件，因此应该经历更高的空间记忆的需求比他们更南部的同种。 为了确定北方山雀和南方山雀之间的记忆和海马体的差异是否已经进化，将进行一个共同的花园实验，其中北方和南方黑顶山雀从巢中取出，并在相同的实验室条件下人工饲养，以检验适应性特化假说的两个预测：（1）北方群体的个体应具有相对较大的海马、较多的神经元和较高的细胞增殖率;（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更大选择压力而进化而来的，因此它们具有遗传基础。 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。 拟议的活动将提供跨学科的研究培训，一名博士后助理，2-3名本科生和1-2名实习生从社区学院每年。将尽一切努力从生物科学领域任职人数不足的群体中征聘候选人担任这些职位。 研究结果将在国家和国际会议上发表，并发表在同行评审的期刊上。拟议研究的结果和理由将通过一个可免费访问的网站、大众媒体的出版物、在当地社区学院的介绍和通过本科生课程的教学，向更广泛的受众提供。所有处理过的脑组织将用于本科生和研究生的教学。这项拟议中的研究是跨学科的，它将加强行为生态学，神经生物学和内分泌学领域之间的整合。

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.