Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.

ORCID

https://orcid.org/0000-0001-6110-1225

Document Type

Open Access Thesis

Embargo Period

4-8-2019

Degree Program

Neuroscience & Behavior

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2019

Month Degree Awarded

May

Abstract

This study examined the relationships between motivation and cognitive performance in male and female common marmosets (Callithrix jacchus). This question was driven by prior data from the Lacreuse lab showing a robust female impairment in reversal learning, as assessed by the number of trials needed to acquire a reversal following a simple discrimination between two stimuli. This thesis tested the hypothesis that the female impairment in reversal learning was mediated by deficits in motivation. Two sets of measures were used to test this hypothesis. I evaluated physical effort via testing on the progressive ratio (PR), a test that requires animals to produce an increasing number of responses to get a reward. Cognitive effort was evaluated through the number of refusals (aborted trials) produced during performance of a reversal. Because estrogen replacement was previously shown to impair reversal learning in ovariectomized females, I also examined whether PR performance was affected by estrogen levels in a subset of female subjects.

Contrary to my hypothesis, reversal learning was not significantly associated with cognitive or physical effort in either males or females. Estrogen levels did not significantly affect physical effort, but there was too much variability in a small sample of females for these results to be compelling. We conclude that the sex difference in reversal learning performance is unlikely to be mediated by sex differences in motivation. Instead females may be more likely than males to engage in habitual processes implicating the dorsal striatum, likely through the action of estrogens on this brain region.

First Advisor

Agnès Lacreuse

Second Advisor

David Moorman

Third Advisor

Matt Davidson

Share

COinS