Spatial representation from birth to old age: Insights from comparative neurobiology and behavioral genomics.

Finding one’s way back to a safe refuge or recalling the best place to find food is essential to all animals including human beings. We engage in future actions based on past events. So how does our brain compute such important cognitive tasks? Is it an innate ability we have from birth that is hardwired into the blueprint of our brains? And what happens if for some reason we realize that we are unable to perform these cognitive abilities in old age or due to a neurological disorder? The hippocampus is the main area of the brain involved in memory and learning. Animal studies show evidence of its role in spatial navigation and memory. The complex network of spatial cells in the hippocampus, all participate in constructing a cognitive map in the brain, where an animal stores information about the external environment and uses it to engage in future actions. However, despite the importance in its function, the hippocampus is also one of the first areas of the brain to be affected by aging and other neurological disorders. The present thesis used the help of various animal models to answer three questions: first whether hippocampal function is present immediately at birth, second whether genes can regulate hippocampal activity and third whether a sensitive task such as reorientation can highlight hippocampal alteration caused by age. To answer the first question, we used the domestic chick that has the advantage of being tested after hatching. We show evidence that a change in environmental shape can alter hippocampal activity in naïve chicks, suggesting that hippocampal function is present already in early stages of life. Furthermore, we investigated if genes regulate hippocampal activity. We used a mouse model that carried one half of the Williams syndrome deletion, a disorder known for its hippocampal deficit. We show evidence that genes on the proximal deletion of Williams syndrome deletion, can alter reorientation and episodic memory, two hippocampal related functions. Finally, we aimed to find an appropriate task to highlight the allocentric difficulty that arises in age. We used aged animals of two species (mice and rats) and tested them in the reorientation paradigm. We show that this simple task has potential to be a better suited assay to evaluate hippocampal behavior.