Thomas Coleman will present his work during the poster presentation of the Mary Gates Undergraduate Research Symposium. Thomas' abstract is reprinted below.
· Thomas (Tom) Coleman, Senior, Psychology
· Sheri Mizumori, Psychology
· Marsha Penner, Psychology
The hippocampus is well known for its role in spatial memory. A better understanding of how the hippocampus functions will provide us with insight into how memories are made and stored. This knowledge may ultimately lead to improved preventative and treatment strategies under conditions in which the hippocampus is altered, such as after traumatic brain injury or in cases of age-related memory impairment. Within the hippocampus there are cells commonly known as “place cells”. These cells are most likely to fire when a navigating organism is in a certain space in an environment, known as that cell’s “place field”. The activity of place cells may be modulated by dopamine input, which can be released tonically or phasically. For example, when overall dopamine input from the ventral tegmental area is disrupted, the place fields of cells within the CA1 subregion of the hippocampus are disrupted and spatial memory deficits occur. To test the idea that phasic dopamine, in particular, is necessary for normal place cell activity and spatial memory performance, we tested spatial working memory while recording electrophysiological activity of neurons in the hippocampus in normal mice and genetically engineered ‘knockout’ mice whose phasic dopamine signaling was selectively disrupted. Preliminary electrophysiological results show differences between the groups, including a nearly significant increase in the spatial selectivity that corresponds to a significant decrease in the size of place fields from the knockout mice when compared to controls. Behaviorally, knockout mice adapt more quickly than control mice following a change in the location of a reward, indicating that phasic dopamine input is not required to perform this task. Rather, removal of the phasic firing pattern may have unmasked a potential facilitating role of tonic dopamine release in flexible goal directed behaviors.