|M.Sc Student||Ben Yishay Elhanan|
|Subject||Space Coding in the Japanese Quail (Coturnix japonica)|
|Department||Department of Medicine||Supervisor||Professor Yoram Gutfreund|
|Full Thesis text|
The hippocampal formation is one of the most ancient structures in the vertebrate brain, sharing functional and developmental similarities among virtually all studied vertebrates, where it is implicated to have an imperative role in memory and navigation. With their seminal discovery of place cells (neurons that show an increased firing rate in a specific location in the environment) in the hippocampal formation of freely moving rats, O’Keefe and Dostrovsky (1971) provided the groundwork to decades of hippocampal research, leading to the discovery of head-direction cells, grid cells, border cells, and more. Thus, over the past half-a-century, the hippocampus has been established as the locus of the so-called cognitive map - a map-like representation of the environment, linking memories and context, presumed to exist in the hippocampus of rodents, bats, primates, and some claim even in humans. However, the absolute majority of studies focused on the hippocampal formation of mammals - this is even though hippocampal homologues exist in a wide variety of vertebrates, such as turtles, birds, and fish; and even though it is established experimentally that the hippocampus serves a similar purpose among all researched vertebrates. Therefore, we decided to explore the role of the hippocampal formation in birds, specifically choosing the Japanese quail as an animal model. By adapting research methods established and utilized in rodents, we were able to record neurons from the hippocampal formation of freely-behaving Japanese quails, and correlate the firing pattern with a variety of behaviors. Our main finding concerns the discovery of head-direction modulated responses, wherein a cell increases its firing rate as a function of the animals’ looking direction in the environment. This is similar to head direction cells found in rodents - however, the cells detected by us had a much wider tuning curve towards a specific area of the environment. Nevertheless, a significant population of recorded hippocampal cells (~10%) showed this type of spatial modulation, thus providing evidence as to the existence of a similar spatial representation system in the hippocampal homologue of other vertebrates.