Inclusion Criteria:

• patients attending Liver Clinic at Toronto Western Hospital, Toronto, ON, Canada
• Fluent in English
• Men and women between the ages of 18 and 65
• Subjects must provide written informed consent to participate
• Control subjects: negative for both HBV, HCV, and HIV

Additional Inclusion Criteria For HCV and HBV patients:

• patient is a candidate for antiviral treatment
• non-cirrhotic as determined by recent liver biopsy (<2 years prior to assessment)
• HCV subjects: positive for HCV RNA, negative for HBV and HIV
• HBV subjects: positive for HBV RNA and negative for HCV and HIV

Exclusion Criteria:

presence of any of the following medical conditions:

• Thyroid dysfunction, or other endocrine disorder
• Major psychiatric disease, especially major depression and bipolar disorder
• Vitamin B12 or folate deficiency
• Unstable cardiovascular disease (especially atrial fibrillation)
• Unstable diabetes
• Haemophilia (depending on frequency of medication usage)
• The presence of other viral infections (HIV; syphilis)
• Use of pharmaceuticals known to affect cognitive function
• Current alcohol use greater than 2 units per day, or prior history of alcoholism
• Use of illicit drugs within 2 years, or prior prolonged history
• History of intravenous drug use within the past 5 years
• History of any of the following neurological conditions: head injury with loss of consciousness greater than 30min., history of stroke, dementia, seizure disorder,recent substance abuse disorder (within 2 years), learning disability
• Postmenopausal and perimenopausal female participants, unless hormone replacement therapy has been administered consistently for 2 years (on the basis that they may have concentration and memory dysfunction related to cholinergic deficits)