Inclusion Criteria:

1. English-speaking Relapsing-Remitting MS (RRMS; intermittent symptom exacerbations followed by periods of remission) patients. 2. Male and female, between the ages of 18-55 years old will be recruited from the Texas Institute for Neurological Disorders (TIND) and MS Clinic of The University of Texas Southwestern. Study referrals will come from board-certified neurologists. 3. Patients will have a McDonald-criteria diagnosis of RRMS, be >30 days past exacerbation and corticosteroid treatment. 4. Included patients will also be free of substance abuse and significant medical, other neurological, or psychiatric conditions unrelated to their MS disease course. 5. Patient selection will be limited to patients that are treatment naïve (i.e., have not been previously treated for their MS) or require a change in treatment course. 6. A clinical determination is needed as to whether ozanimod is the best treatment for a patient or whether a patient requires treatment change to ozanimod. 7. All included participants will be right-handed and at least high-school educated. 8. Only patients who score above 25 on the Telephone Interview for Cognitive Status (TICS) will be included.

Exclusion Criteria:

1. During calibrated functional magnetic resonance imaging (fMRI) scanning, participants will inhale a carbon dioxide/room air solution to allow for calibration of BOLD signal. Thus, to ensure participant safety, the investigators exclude: smokers and those with MR-contraindicators, any participants with a history of respiratory or pulmonary problems (e.g., asthma, Chronic Obstructive Pulmonary Disease (COPD), sarcoidosis, tuberculosis), any participant with a history of cerebral vascular disease (e.g., cardiac disease, transient ischemic attack, migraines, stroke, arteriovenous malformation), any participant with a history of respiratory or pulmonary problems (e.g., asthma, Chronic Obstructive Pulmonary Disease (COPD), sarcoidosis, tuberculosis), and any participant with a history of cerebral vascular disease (e.g., cardiac disease, transient ischemic attack, migraines, stroke, arteriovenous malformation). 2. Participants that present with EKG abnormalities consistent with FDA labeling contained within the ozanimod guidelines will be excluded as these abnormalities may be indication of dangerous negative side effects upon ozanimod consumption. EKG abnormalities include presence of atrioventricular (AV) block, sick sinus syndrome, or sino-atrial block. Any experiences of myocardial infarction, unstable angina, stroke, transient ischemic attack, decompensated heart failure requiring hospitalization, or Class III or IV heart failure within the last 6 months will exclude the patient. Contraindicators of ozanimod that may be found in the blood sample include presence of varicella titers and enzyme/protein levels that indicate liver dysfunction. Thus, these participants will be excluded. 3. Patients who exhibit diseases other than MS that may be responsible for the patient's clinical, or MRI presentation will be excluded. 4. Patients who exhibit a history of hypersensitivity to ozanimod or any drugs of similar chemical classes (i.e., sphingosine phosphates) will be excluded. 5. Female participants who are pregnant or nursing will be excluded from the study. After the participant consents to being in the study, there will be a screening appointment to determine their eligibility, at which a pregnancy test will be provided. Other examinations, such as neurological assessments and EKGs, will occur at this appointment. 6. Patients who are not native-English speakers will be excluded, as their English ability may limit their understanding of the instructions and performance on the neuropsychological tests. 7. Patients who score below 25 on the Telephone Interview for Cognitive Status (TICS) will be excluded.

To assess MS patients' cognitive improvement while on ozanimod, the investigators will compare MS patients' baseline performance to the patients' performance following treatment on memory, processing speed, verbal ability and executive function. The investigators predict that cognitive performance will improve during the ozanimod treatment compared to the baseline. Baseline-treatment differences will be assessed using repeated-measures analysis of covariance (ANCOVA) while also controlling for effects of age, education, disease duration, and expanded disability status score (EDSS). The investigators predict that improved cognitive performance will be accompanied by improvements in brain structure (e.g., increased whole brain volume) and function metrics. Thus, each MS patients' brain volume, white matter connectivity, lesion load, and resting BOLD at baseline, during treatment, and after ozanimod treatment will be measured. For each structure and function MR metric, baseline-treatment differences will be assessed using repeated-measures ANCOVA while also controlling for effects of age, education, disease duration, EDSS and brain parenchymal fraction (the ratio of functional brain tissue to whole brain volume).

Arms

Experimental: Ozanimod

Participants will receive Ozanimod and work up to .92 mg. They will then take one pill daily for a duration of 12 months.

Interventions

Drug: - Ozanimod

A hard capsule that is taken daily for one year.