Date of Award

December 2014

Degree Type


Degree Name

Master of Science



First Advisor

Rodney Swain


Dentate Gyrus, Hippocampus, Memory, Neural Circuits, Neurogenesis


Work with patient H.M. sparked great interest in the role of the hippocampus in learning and memory. Later, the findings that new neurons are born in the adult dentate gyrus (DG) and that they become functionally integrated in neural circuits created new excitement in the field of learning and memory. While there is ample evidence that the hippocampus and adult neurogenesis are involved in learning and memory, similar inconsistencies in both areas have clouded interpretations of their precise role. We propose that studying the role of hippocampus and neurogenesis in the DG must be merged into a more cohesive field of study. The neural circuit between the hippocampus and new neurons born in the DG form a network crucial for detailed memories and behavioral flexibility. The immature and highly excitable adult-born principle cells in the DG make up the active population of principle cells in the DG while the more mature cells are relatively silent. The young and excitable adult born cells initially form synapses with other cells. These synapses with cells that have pre-existing synapses may allow for the reinstatement and strengthening of old as well as the ability to acquire new learning in a familiar context. Despite extensive inputs to the DG, the only output of the DG is to the hippocampus. The hippocampus has extensive inputs and outputs with numerous brain regions making it suitable to serve as an index of memory representations. Thus, any information processed in the DG must be sent to the hippocampus which is in turn capable of indexing detailed memory representations and flexible behaviors.