Dissertations, Theses, and Capstone Projects

Date of Degree

9-2026

Document Type

Master's Thesis

Degree Name

Master of Science

Program

Cognitive Neuroscience

Advisor

Jeff Beeler

Subject Categories

Cognitive Science

Keywords

dopamine, acetylcholine, cholinergic interneurons, D2 receptor, matching law, choice behavior

Abstract

Dopamine (DA) and acetylcholine (ACh) interact within the striatum to shape reward-based learning and choice behavior. DA D2 receptors on cholinergic interneurons (CIN D2Rs) were genetically knocked out to investigate their role in choice allocation using a two-lever matching paradigm. Behaviorally, both knockout (KO) and wild-type (WT) mice learned the initial task equally well. When shifted to asymmetric matching schedules (VI-90 vs. VI-180), ideal matching predicts that mice should allocate exactly 67% of their total responses to the rich lever. Neither group matched as predicted by the matching law. Instead, the KO mice showed a pattern where the higher rate of reward had a disproportionate effect on their effort allocation, leading them to over-match by directing approximately 80% of their effort to the rich lever. The WT mice distributed their effort more equally between the two levers, essentially under-matching by splitting their choices roughly 50/50. Overall reward consumption and eating pace remained the same between genotypes. Ultimately, the genotypes looked more similar than different, and any observed effects were modest, suggesting the impact of deleting D2R from CINs may be limited due to either redundant or compensatory systems.

Download

Share

COinS