A Novel Role for Adult Neurogenesis in a Two-Armed Bandit Reversal Learning Task

Huntzicker, Kathleen Beth

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Year:: 2023
Contributor:: Huntzicker, Kathleen Beth (creator); Cameron, Heather (Advisor); Averbeck, Bruno (Reader); Burwell, Rebecca (Reader); Penzo, Mario (Reader); Grissom, Nicola (Reader); Brown University. Department of Neuroscience (sponsor)
Genre:: theses
Subject:: Adult Neurogenesis; behavioral neuroscience; Two-Armed Bandit; Hippocampus (Brain); Dentate Gyrus; Reversal Learning
Extent:: xiii, 130 p.

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Abstract:: Neurogenesis in the mammalian hippocampus persists throughout adulthood, but the function of newly-born hippocampal cells remains largely unknown. This dissertation investigates the effects of neurogenesis ablation on rodent decision-making. By studying the choices of rats with and without new neurons, we can gain a better understanding of how neurogenesis influences behavior. Neurogenesis ablation was achieved using a pharmacogenetic method. Transgenic rats expressing the herpes simplex virus thymidine kinase gene under the control of the human glial fibrillary acidic protein (GFAP) promoter were given an antiviral drug to induce complete ablation of hippocampal neurogenesis. This method is both time- and cell type-specific: cell division (and therefore neurogenesis) is disrupted only upon drug administration, and only in neural precursors, which express GFAP. Treated transgenic (TK) rats are not impaired on many standard learning tasks; however, previous work indicates that TK rats respond differently than wild-type (WT) controls when faced with situational uncertainty. To further explore this effect, I used a two-armed bandit reversal learning task to confront rats with frequent ambiguous feedback. On the standard version of the task, rats learned that one lever produced a food reward 80 percent of the time, and the other, 20 percent. At multiple intervals throughout each test session, the lever contingencies switched. Thus, a previously lucrative lever failing to deliver a reward could indicate either a reversal, or merely the 20 percent chance that the “better” lever would produce no reward. On several versions of the bandit task, TK rats outperformed WT controls, earning more rewards – a departure from most prior literature, in which neurogenesis ablation usually confers a behavioral disadvantage. The performance difference was largely attributable to superior decision-making strategy. Notably, the effect persisted even when lever contingencies were deterministic, but was attenuated when reversal frequency was increased. These findings and others included within the dissertation prove that the behavioral effects of neurogenesis loss are not always detrimental. Furthermore, the ways in which new neurons influence decision-making are dependent on sex, situational uncertainty, and specific task constraints – demonstrating a nuanced yet important role for neurogenesis in determining animal behavior.
Notes:: Thesis (Ph. D.)--Brown University, 2023

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Huntzicker, Kathleen Beth, "A Novel Role for Adult Neurogenesis in a Two-Armed Bandit Reversal Learning Task" (2023). Neuroscience Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:nmnz565y/

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Neuroscience Theses and Dissertations

Theses and Dissertations for the Neuroscience department.
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