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

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

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.