Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis


Arts and Sciences



First Advisor

Dr. Joshua Beckmann


Opioid Use Disorder is characterized partially as a decision-making disorder. Decision-making theories, such as habit theory and relative value theory, have aimed to better understand the shift in preference for drug over other alternatives. In order to compare these two contrasting theories, an allomorphic concurrent choice task will run in tandem with an escalation procedure. Male and female Sprague-Dawley rats were tested for choice differences in an allomorphic choice procedure. Reward dimensions, such as relative reward rate, were manipulated within sessions, and magnitude (remifentanil dose), was manipulated between sessions. To study the effects of escalated fentanyl intake on relative valuation, rats completed choice procedures in the morning, followed by either 1-hr or 6-hr access to fentanyl in the afternoon.

Escalation of fentanyl intake was evident in the 6-hr fentanyl access group, meanwhile fentanyl intake remained stable in the 1-hr fentanyl group. Choice behavior between 1-hr and 6-hr fentanyl access groups did not differ, however model comparison differences were found such that the model that included food-condition best described escalation data, but not choice data. This major finding indicates that value-based decision-making processes remained intact in 6-hr fentanyl access rats despite escalated intake of fentanyl, thus failing to support habit theory.

Digital Object Identifier (DOI)

Funding Information

This study was supported by the National Institute of Health (NIH) R01 grant (DA047368-01) in 2020-2023.