His research follows two broad strands. The first focuses on the search for cerebral correlates of behavioral disorders associated with multiple sclerosis. His neuroimaging (MRI) studies, have helped define the structural brain changes associated with depression in people with MS. His lab has developed novel, computerized neuropsychological assessments that are sensitive to cognitive impairment in people with MS. Current work has elucidated the functional brain changes and cognitive dysfunction secondary to cannabis use in people with MS. He is the principal investigator on a six country, 11 centre neuro-rehabilitation study investigating the potential cognitive benefits of combined aerobic exercise and cognitive rehabilitation in people with a chronic progressive disease course.