Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Master of Science




Melling, Jamie CW


This study examined the impact of Type 1 Diabetes Mellitus (T1DM) on executive function using a series of operant conditioning based tasks in rats. Sprague Dawley rats were randomized to either non-diabetic (n = 12; 6 male) or diabetic (n = 14; 6 male) groups. Diabetes was induced using multiple low-dose streptozotocin injections. All diabetic rodents were insulin-treated using subcutaneous insulin pellet implants. At week 14 of the study, rats were placed on a food restricted diet to induce 5 - 10% weight loss. Rodents were familiarized and tested on a series of tasks that required continuous adjustments to novel stimulus-reward paradigms in order to receive food rewards. No differences were observed in the number of trials, nor number / type of errors made to successfully complete each task between groups. Therefore, we report no differences in executive function, or more specifically set-shifting abilities between non-diabetic and diabetic rodents.

Summary for Lay Audience

Type 1 Diabetes Mellitus (T1DM) is a disease in which the body loses the ability to produce insulin, a hormone that helps regulate blood sugar and provides energy to bodily tissues. Although there is no cure, patients with T1DM can lead a relatively normal life thanks to the invention of pharmaceutical insulin. However, T1DM increases risk of both short- (seizure, diabetic coma) and long-term (heart disease, vision and nerve problems) health complications. There have also been several studies that have demonstrated that patients with T1DM have minor brain abnormalities that may impair cognition. Research in both humans and animals has shown that T1DM is associated with decreased performance in tests of intelligence, information processing, and cognitive flexibility. Cognitive flexibility (also referred to as set-shifting) measures one’s ability to adapt to changing circumstances or “outside of the box thinking”. Many prior studies in animals have examined cognition, however very few have used tests that specifically assessed cognitive flexibility. Furthermore, very few animal studies have used rodents that were insulin-treated, the standard treatment for patients with T1DM. Therefore, the purpose of this study was to test the set-shifting abilities of insulin-treated T1DM rats compared to non-diabetic rats. Rats were randomly divided into two groups: twelve non-diabetic (six male, six female) and fourteen diabetic (six male, eight female). At week 14 of the study, rats were put on a food restricted diet to help motivate them to complete the set-shifting tasks. Once they lost 5% of their body weight, rats were familiarized with the testing apparatus and then progressed through three unique tasks. Each task corresponded to a specific rule that the rat must learn in order to receive a food reward. The number of trials it took for the rat to fully learn the rule, as well as the number of errors they accrued in learning the rule were recorded. There were no differences in either measure across the three tasks that were completed. Therefore, we conclude that insulin-treated T1DM rats do not show any decreases in cognitive ability, or more specifically set-shifting, compared to non-diabetic rats.