Change in the Cerebellum Predicts Change in the Orbitofrontal Cortex in a 3-year Longitudinal sMRI Cannabis Study: A Push for the Integration of the Cerebellum into the I-RISA Model of Addiction

Abstract

The cerebellum is the dark horse of neuroscience, increasingly sparking research interest amongst psychologists and neuroscientists for its growing involvement in a vast array of social, cognitive and behavioral functions. Although previous focus on the role of the cerebellum was constrained to its modulation of sensorimotor learning and processing, a growing body of literature is now interested in the role of the cerebellum in numerous neurological disorders, namely its role in substance use disorder (SUD). Very little is known about the role of the cerebellum in SUD and in this study, structural MRI data observing cannabis use over a 3-year period (CB=20 and HC=22) was assessed in order to better understand cerebellar involvement in SUD. The purpose of this study was to provide evidence for the argument that the cerebellum ought to be included in the I-RISA model of addiction. Overall the thesis provides partial evidence in support of this argument by demonstrating that several cerebellar regions of interests (ROIs) disrupted by cannabis use go on to predict structural change in OFC over time. These cerebellar ROIs include the right crus I, right lobule VI and right lobule VIIIa, left lobule VI, left lobule VIIIb and left cerebellar WM. Cortical thickness maps also showed that the middle temporal gyrus undergoes cortical thinning in cannabis users in comparison to healthy controls. The thesis goes on to highlight limitations of the study and offers future directions for research that could satisfy existing questions concerning the role of the cerebellum in addiction-related processes vis-à-vis the I-RISA model.