Inclusion Criteria:  Adults ≥ 18 years < 75 years. Clinical diagnosis of RA Selected to start Olumiant by their usual rheumatology clinical team in line with local guidance (previous failure of at least 2 DMARDs and moderate to severe disease active disease) Right-handed (to reduce neuroimaging heterogeneity)  Exclusion Criteria:  Inability to provide written informed consent. Severe physical impairment (e.g. blindness, deafness, paraplegia). Pregnant or breast feeding. Contraindications to MRI (e.g. severe claustrophobia). Major confounding neurological disease including Multiple Sclerosis, Stroke, Traumatic Brain Injury, Parkinson's Disease, Alzheimer's Disease Previous targeted synthetic (e.g. Oluminant, tofacitinib) DMARD exposure. Co-morbid medical conditions that may significantly impair physical functional status Medical or psychiatric conditions that in the judgment of study personnel would preclude participation in this study (e.g., malignancy, psychosis, suicidal ideation) BMI > 40 or unable to lie comfortably in MRI