This study will determine the effects that HIV and hepatitis C virus have on thinking abilities and whether the viruses affect brain chemistry.

Hepatitis C is a liver disease that is caused by the hepatitis C virus (HCV). It can be successfully treated with 6 to 12 months of medication in both HIV infected and HIV uninfected people. Among HIV infected people, HCV infection is a common co-morbidity, and is more serious when it occurs in this population than others because it leads to liver damage more quickly. HIV is known to cause neurological deficits, and studies suggest that HCV may do so, as well. Knowledge about how to treat these deficits, however, is limited. More information about the nature of the neurological problems and their causes is needed to develop effective treatments. This study will determine the effects that HIV and HCV have on thinking abilities, such as memory, attention, and problem-solving, and whether the viruses affect brain chemistry.

Participants in this 4-year, observational study will undergo a series of tests and interviews. Participants may choose to complete all procedures over 2 days or three appointments. Procedures will include a 20-minute medical interview, a 4-hour neuropsychological evaluation, a 5-minute functional ability questionnaire, blood and urine collection (approximately 15 minutes), and a 1-hour magnetic resonance imaging (MRI) test of the head. The neuropsychological evaluation will test participants' memory, concentration, reasoning, and speed of thinking. All procedures will be completed over approximately 6 hours.

Inclusion Criteria:

• CD4 count is greater than 200
• Hepatitis C infected or uninfected
• Speaks English

Exclusion Criteria:

• Currently receiving interferon treatment for hepatitis C
• History of neurological illness
• Any psychotic spectrum disorder (e.g., schizophrenia or manic depression/bipolar disorder)
• History of learning disability
• History of head injury that entailed a loss of consciousness for more than 30 minutes
• Any metal in body

HIV / HCV Coinfected, HIV moninfected, & HCV monoinfected