Alsasha Gangloff

University Honors with Honors in Psychology

Major: Psychology

Supervisor: Julian Keith, Psychology

Is the Population of Immature Neurons in the Adult Rat Hippocampus Increased by Environmental Variability?

Neurogenesis, the production of new neurons, continues throughout adulthood in the dentate gyrus, a subregion of the hippocampus. The hippocampus is located in the medial temporal region of the mammalian brain and plays an important role in interpreting and storing information about the environment and cell activity in the hippocampus is strongly influenced by our surroundings. Previous research has found evidence that environmental factors may play a role in the production and survival rates of immature neurons that are born in the dentate gyrus during adulthood. The experiment conducted for this thesis investigated the effects of exposure to varying exploratory environments on the population of new neurons found in rats’ hippocampi. Rats in the control group remained housed in standard laboratory chambers, while rats in the experimental groups were exposed daily for 10 days to either one or three enriched chambers which consisted of a placed in spatially complex locations and containing a variety of objects and scents. Based on the previous research, we predicted that the number of environments the rats were exposed to would influence the population of new neurons, and that a larger pool of immature neurons would be observed in rats that were exposed to more environmental variability. Immunohistochemistry techniques and both bright field and florescent microscopy methods were used to identify cells expressing protein markers known to be unique to immature neurons (doublecortin) and cells less than two days old (Ki67). Surprisingly, the pools of doublecortin- and Ki67-positive cells were unaffected by the number of different environments the rats were exposed to. I will provide potential explanations for why the present study did not detect a link between the populations of immature neurons observed in the hippocampus and the numbers of different environments rats experienced.