Evaluate the Effects of Tolcapone on Cognitive and Behavioral Dysfunction in Patients With BI and NCD

TBI and ABI Patients Inclusion Criteria * Age 18-70 * Diagnosis of mild, moderate, or severe TBI, or history of ABI with classification to be made based on parameters at the time of the index event or acquired brain injury. * Index event resulting in Traumatic or Acquired Head Injury occurred \>12 months prior to trial initiation * A current or former patient at the clinics of the Sheppard Pratt Neuropsychiatry Program or another Sheppard Pratt outpatient clinic with medical documentation of TBI or ABI * Proficient in the English language * Available to come to Sheppard Pratt Towson for the baseline evaluation and testing and for the duration of the protocol * Stable neurological and psychiatric symptomatology for 2 months prior to trial initiation as determined by the referring Sheppard Pratt physician. * Stable medication dose and regimen for 2 months NCD Patients Inclusion Criteria * Age 60-75 * NCD diagnosed by a Sheppard Pratt physician, per DSM-5 * No abnormalities on other serum tests to rule out other cause of cognitive impairment: TSH, B12, CBC, Chemistry screen, and RPR. * Recent structural neuroimaging (within 1 year or since the time of the onset of cognitive complaint)-noncontrast head CT or MRI-to rule out any gross lesion inconsistent with the diagnosis of MCI (e.g. subdural hematoma, normal pressure hydrocephalus, demyelinating lesion, infarct, or mass lesion) * Proficient in the English language * A current or former patient at the clinics of the Sheppard Pratt Neuropsychiatry Program or another Sheppard Pratt outpatient clinic with medical documentation of NCD * Available to come to Sheppard Pratt Towson for the baseline evaluation and testing and for the duration of the protocol * Stable neurological and psychiatric symptomatology for 2 months prior to trial initiation as determined by the impression of the referring Sheppard Pratt physician. * Stable medication dose and regimen for 2 months Exclusion Criteria for All Patients: * History of, or active, liver disease or abnormal liver function tests--if the patient currently has elevated Alanine Transaminase (ALT) or Aspartate Transaminase (AST) levels that exceed 2 times the upper limit of normal \[Normal Reference Ranges ALT (Male: 4-40 IU/L, Female: 4-40 IU/L), AST (Male: 4-31 IU/L, Female: 4-37 IU/L) or the ratio of AST:ALT has exceeded 2:1 * Active alcohol use disorder, as defined by DSM-5, of any severity mild, moderate, or severe * History of, or active, cardiovascular disease defined as: coronary heart disease, manifested by myocardial infarction, angina pectoris, or heart failure * Uncontrolled hypo-or hypertension based on Joint National Committee criteria (JNC7) Hypotension: Systolic\<90mmHg or diastolic\<60mmHg Hypertension: Systolic \>140mmHg or diastolic\>90 mmHg) * History of extra-pyramidal symptoms (e.g. tardive dyskinesia, neuroleptic malignant syndrome, or QT prolongation) while on a first-generation anti-psychotic * Active illicit substance use, resulting in a substance use disorder as defined by DSM-5, of any severity mild, moderate, or severe * Patient is currently taking tolcapone or any of the following medications that can interact with tolcapone resulting in an adverse events: another COMT inhibitor, benserazide, α-methyldopa, dobutamine, apomorphine, isoproterenol, clozapine, MAO inhibitor * Known allergy or serious adverse reaction to tolcapone * Participated in any investigational drug trial in the past 30 days. * Pregnant or planning to become pregnant during the study period * Breastfeeding or planning to breastfeed during the study period. Other Exclusion Criteria for TBI Patients • Presence of pre-morbid/pre-TBI cognitive impairment or behavioral dysfunction, as per informant or medical documentation