Date of Completion

2021

Document Type

Honors College Thesis

Department

Psychological Sciences

Thesis Type

Honors College, College of Arts and Science Honors

First Advisor

Donna Toufexis

Keywords

Estrogen, Progesterone, Habit Formation, Instrumental Learning, Dopamine, Dorsal Striatum

Abstract

Behavioral motor outputs transition from goal-directed to habitual following extended instrumental training, and is related to increases in dopamine (DA) release in the dorsal striatum. DA signaling in this region is positively correlated with circulating estrogen (E2) levels. Previous studies in our laboratory used lithium chloride (LiCl) reinforcer devaluation (RD) to identify habitual behavior in ovariectomized (OVX) female rats, and found that replacement with E2 resulted in goal-directed responding after a level of training where intact females express habitual behavior. The present study was designed to determine whether ovariectomized female Long Evans rats with estrogen and progesterone (E2+P) replacement during acquisition demonstrate habitual behavior following the same level of training. Results indicate that E2+P replacement supports the development of habitual (RD-insensitive) responding in female rats. These data suggest that the cyclic variation of both estrogen and progesterone throughout the estrus cycle and, possibly, their impacts on dorsal striatal DA underlie the sex-differences seen in the formation of habit.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

Available for download on Saturday, May 14, 2022

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