Publication Date

2025

Document Type

Dissertation/Thesis

First Advisor

Matuszewich, Leslie

Degree Name

M.A. (Master of Arts)

Legacy Department

Department of Psychology

Abstract

Motivation is a complex concept that contributes to or is embedded within many different behaviors. As such, it can be difficult to assess motivation directly, but many researchers have attempted to measure motivation to understand its role in behavior and in diseases associated with a dysregulation of motivation, such as drug addiction or depression. To better understand motivation, behavioral tests frequently use palatable foods to measure motivation as defined by the amount of effort a rat will demonstrate to achieve the reward. Much of research has focused on highly controlled experimental settings, such as lever pressing in an operant box where the assessed behavior may not be intuitive to organisms being tested. Therefore, it is valuable to assess motivation through novel tests that require ethological behaviors, as well as those documented in the laboratory. Acute stressors have previously shown to affect motivation, with some studies showing an increase and others showing a decrease in motivation for a palatable reward. Little research has examined motivation following stress by assessing ethological behaviors such as string-pulling, in male and female rats. The current proposal tests the motivation of male and female rats in an operant box paradigm and string-pulling paradigm under control and acute stress conditions. In both male and female rats, yohimbine increased correct lever presses (p < 0.001) and showed higher progressive ratio values (p < 0.001), compared to rats injected with saline when tested in the operant box; however, no sex differences were observed. In contrast, there was a significant difference between male and female rats in the string length pulled (p < 0.001), with females pulling in more string than males; however, no effect of drug (p = 0.86) in the string-pulling test. Overall, these results suggest that the approach of assessing motivation may be critical to understanding the effects of acute stress for both male and female rats. In considering differences in behaviors between male and female rodents, it may be important to adapt the parameters of behavioral tests to each sex to fully understand the impact of acute stress on motivation for food rewards.

Extent

70 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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