Patient description: A 53-year-old man presents with chronic HCV infection for the past 2 years. His past medical history is only significant for inguinal hernia surgery when he was 20 years old. He is on IFN (100 mg/week) plus RBV (400 mg/day) combination therapy for the past 9 months. Direct antiviral drugs were added to his treatment 6 months ago. His medical record shows previous positive HCV RNA tests as well as positive enzyme immunoassay for anti-HCV-antibodies. The recent biopsy was negative for hepatocellular carcinoma and was only remarkable for chronic inflammation compatible with a chronic viral hepatitis. There is no evidence of alcoholic liver disease, bleeding from esophageal varices, hemochromatosis, autoimmune hepatitis or metabolic liver disease. He is an alert male with no acute distress. His BP: 130/75, HR: 90/min and BMI: 27. His abdomen is soft with no ascites or tenderness. The lower extremities are normal with no edema.

Clinical trial eligibility criteria: eligible ages (years): 18.0-65.0,  Normal Physiology FOR ALL A subject can be included in this study if he/she is in good general health is between 18 and 65 years old is capable of understanding the procedures and requirements of this study is willing and able to provide his/her own informed consent; FOR IN-LAB has visual acuity of 20/40 in at least one eye (corrected with contact lenses is okay) has no hearing impairment requiring a hearing aid. FOR IN-LAB A participant is not eligible for participation in the in-lab portion of this study if any of the following  are present, as self-reported by the prospective participant or determined during clinical testing following consent Participant has serious vision or hearing problems; for some sub-studies focused on color vision, subjects who are colorblind will also be excluded Participants without consent capacity will not be enrolled Participant has a neurological disorder (examples but are not limited to: epilepsy, schizophrenia, Alzheimer s Disease, Parkinson s Disease, multiple sclerosis) or a psychiatric disorder (examples but are not limited to: clinical anxiety, depression, attention deficit hyperactivity disorder (ADHD), schizophrenia) Participant has had a serious head injury or has a history of brain surgery. Head injury is defined as an injury to the brain from some external force resulting in loss of consciousness of 30 minutes or more Participant has psychoactive drug or alcohol abuse or dependence in the past three months, as determined by the Drug Abuse Screening Test (DAST), except nicotine and caffeine. A score of 6 or greater on the DAST will be considered exclusionary. The effects of nicotine and caffeine in neuroimaging are attenuated if participants do not smoke or consume caffeine 2-3 hours before the scan session; Over-the-counter medication/herbals will not be a criterion for exclusion Participant is an NEI employee within the Sensation, Cognition and Action section FOR MRI SUB-STUDIES: Contraindication to MR scanning the following: pregnancy; metallic tattoos or metallic eyeliner; claustrophobia; inability to lie still on their back for ~2 hours; implanted cardiac pacemaker or auto-defibrillator; surgical aneurysm clips; implanted neural stimulator; artificial heart valves or pumps; metal fragments in cranial cavity, body or eyes (e.g., history as a metal worker); nitroglycerin patch (foil backer); cochlear implants (tubes are okay); weight > 450 lbs; metal rods, plates, screws in body; shrapnel or bullet wound; intrauterine device (IUD) not approved on mrisafety.com (most IUDs are okay); vestibular or inner ear abnormality such as Meniere s disease; metallic braces; hair extensions attached with metallic wires; transdermal patches; movement disorders; dental implants; consumed of nicotine or caffeine in the two hours prior to the experimental session. Subjects may participate in this study, but will not be allowed to have a 7.0 T MRI scan if they have metallic dental crowns or a bridge FOR ON-LINE Subjects may not participate in the on-line portion of the study if they Do not have access to compatible equipment. For example, smartphone screens are too small to be used. Amazon MTurk will outline which devices may be used