Electronic Thesis and Dissertation Repository

Thesis Format

Alternative Format

Degree

Master of Science

Program

Neuroscience

Supervisor

Morton, J. Bruce

2nd Supervisor

Martinez-Trujillo, Julio

Co-Supervisor

Abstract

Interference control deficit in Working Memory (WM) is associated with neurodevelopmental disorders. The common marmoset (Callithrix jacchus) is an ideal non-human animal model for studying WM disorders. Previous studies of marmoset WM have used a touch-screen self-ordered sequencing task (SOST), which resembles an n-back paradigm and targets updating processes in internal interference control. However, the training time for the marmoset to reach proficiency on this paradigm is long given the short marmoset lifespan. In an attempt to accelerate marmoset learning of the task, we developed a new version of SOST that relied on foraging behaviour. The goal of this project was to validate an experimental design that resembles the naturalistic environment of the animal and speed up the learning phase of training. A below chance performance was observed. Two task-related issues were identified that could be the reason for poor performance. The training levels were modified to resolve the weaknesses of the task.

Summary for Lay Audience

WM deficit is an identifying feature of neurodevelopmental disorders. Interference control is the ability to control unrelated information and plays a central role in WM functioning. Animal models play a critical role in advancing our understanding of human WM functioning and are essential for interventions in neurodevelopmental disorders. The common marmoset is a relatively new animal model suggested as an ideal model for neurodevelopmental studies. The first step to enhance our understanding of WM functioning in the marmoset and conducting preclinical studies is to validate tasks that target specific WM features and are suitable for developmental studies. The SOST is a task used to investigate WM in the marmoset. This task is based on the n-back paradigm, which is a well-established task used to study interference control in humans. However, a long training period is required, and marmosets have a relatively short lifespan and short developmental periods. Here, a novel task design for the SOST was developed that relied on foraging behaviour and represented the animal's natural behaviour. A naturalistic environment was used in order to accelerate the learning procedure, given the marmosets short lifespan.

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