In addition to psychiatric criteria described above: past or current medical condition that would interfere with brain function - history of alcoholism, tobacco use (must have minimum of one year of full remission/complete abstinence from nicotine), neurological illness, head trauma with loss of consciousness, history of exposure to central nervous system toxin; history of central nervous system infection; metabolic, endocrine, connective tissue disease; hypertension or other cardiovascular disorder; gastrointestinal disorders; abnormal renal, liver or pulmonary function; blood dyscrasias; malignancy; nonstimulant or stimulant pharmacotherapy within 1 month of the study, or any history of antipsychotic medication; neurodegenerative or neurodevelopmental disorder; stroke; epilepsy; sensitivity to flashing lights; subjects requiring regular medication; subjects demonstrated by drug screening to have taken a controlled substance; subjects with a history of hypersensitivity to lidocaine; subjects with IQ less than 80. Females, adolescents and children will be excluded.