The research project will employ a behavioural economic model to investigate the neural substrates of treatment choice and treatment adherence among patients with chronic disease. Adherence researchers frequently use biopsychosocial models to better understand, assess, and treat poor adherence in chronic disease. Yet, very little is known about the neural mechanisms of patient treatment choice and adherence. The project will use functional magnetic resonance imaging (fMRI) to examine brain mechanisms of risk and reward, the proposed study will evaluate a neuroeconomic model of treatment choice and adherence in multiple sclerosis (MS). The aim of the research is to model the behavioural and neural mechanisms associated with how adherent and non-adherent patients weigh potential risks and benefits when making hypothetical treatment decisions as part of a novel fMRI medication probability discounting paradigm.