Inclusion Criteria:  Group A (acute mTBI) Adult (ages 18-55 years) any gender, who is capable of giving informed consent, having neurocognitive testing and questionnaires, able to undergo MRI, and willing to attend at least 3 of the 5 proposed clinic visits at WRNMMC.  Has a mild traumatic brain injury for which the individual sought medical attention in an ED/acute care clinic within 72 hours of injury. Diagnosis of mTBI Acute injury and able to enroll in the study within 11 days from injury.  Group B (Control) Adult (18 to 55 years), any gender, who is capable of undergoing informed consent, having neurocognitive testing and questionnaires, able to undergo MRI, and able to go to WRNMMC for imaging.  Has not had a mild traumatic brain injury in the last 5 years or ever.  Group C (chronic mTBI) Adult (18 to 55 years), any gender, who is able to undergo MRI, and able to go to WRNMMC for imaging, capable of giving informed consent, and having neurocognitive testing and questionnaires.  Injury greater than 6 months but fewer than 5 years ago.  Exclusion Criteria:  Groups A,B,C: Patients with contraindication to MRI (per standard WRNMMC SOP these individuals will not be scanned anyway. Standard WRNMMC MR screening criteria will be used as a part of their normal MR examination- e.g. non-FDA approved pacemakers, aneurysm clips,MR contraindicated metal/metallic devices, etc.). Groups A,B,C: Never had a penetrating, moderate or severe TBI at any time. Groups A,B,C: Unable to tolerate proposed imaging (e.g. severe claustrophobia, unable to tolerate lying flat for duration of MRI). Groups A,B,C: History of pre-existing neurologic condition which would affect the ability to interpret MRI results (such as prior stroke, multiple sclerosis, or brain tumor). Groups A,B,C: Patients requiring anesthesia support for sedation Groups A,B,C: Pregnant patients Groups A,B,C: Any person who is unable to sign/give consent