Memory and the Hippocampus in Twins

Inclusion Criteria

• All twins will be required to give written informed consent.
• Subjects will be included with a history of Vietnam Era service.
• All subjects must be free of major medical illness on the basis of history and physical examination, lab testing, and electrocardiogram.

Exclusion Criteria

• Subjects will be excluded with a history of shrapnel or other foreign bodies that would preclude MRI scanning, history of loss of consciousness, or neuroleptics, sedative or benzodiazepine medication usage within the previous four weeks.
• Subjects will also be excluded if based on the SCID interview they have comorbid:
• schizophrenia;
• schizoaffective disorder;
• bulimia or anorexia, or
• bipolar disorder.
• Subjects will also be excluded with a history of blast injury with associated traumatic brain injury.
• In addition, subjects will be excluded with a history of alcohol or substance abuse/dependence within the past year. We will use the strategy used in prior MRI studies and use multivariate analyses to examine the contribution of past histories of alcohol and substance abuse (as measured with the Addiction Severity Index) and depression symptom level (as measured with the Hamilton Depression Scale) to the outcomes of interest.
• Subjects will be excluded from the study if they present with a history of serious medical or neurological illness, or as a result of routine laboratory studies, history of asthma, steroid usage, seizure disorder, or prenatal/perinatal substance exposure or trauma.