fMRI Study of Nicotinic Effect on Neurophysiology of Schizophrenia

The prevalence rate of smoking among schizophrenia patients is as high as 88 percent. This is associated with a 2-fold increase in deaths due to smoking related diseases-compounded by high rates of nicotine dependence and low abstinence rates following cessation programs. Converging lines of evidence suggest that high rates of smoking and nicotine addiction among schizophrenic patients is influenced by the presence of disease-related abnormalities in brain function. Genetic and post mortem studies show that patients exhibit abnormalities in neuronal nicotinic receptors, which are involved in a number of cognitive functions. Pharmacological studies show that nicotine temporally improves performance in several cognitive tasks including sensory gating, long-term memory, and visual tracking. These data support a growing consensus that smoking among schizophrenic patients is a form of self-medication, and suggest that the success of targeted smoking cessation programs will depend, in part, on finding alternative means of treating the underlying cognitive deficits. One of the most reproducible neurocognitive and biological changes in schizophrenia is abnormal visual tracking, or smooth pursuit eye movements. Preliminary data show that previously reported deficits in visual tracking are related to anticipatory learning deficits and that nicotine enhances performance in patients by temporarily treating this learning deficit. A better understanding of these processes may lead to better behavioral and/or pharmacological therapeutic interventions for excessive nicotine abuse and recidivism in this clinically vulnerable population. In order to identify brain regions underlying this learning deficit we propose to compare brain activations in 30 healthy controls and 30 patients with schizophrenia during anticipation of target motion using functional magnetic resonance imaging (fMRI). In order to identify the brain regions involved in nicotine-induced enhancement of anticipatory learning we will compare activation in patients under conditions of unexpected and anticipated target motion following administration of nicotine and placebo.

• INCLUSION CRITERIA:

Subjects (schizophrenia patients and healthy control smokers) must be between the ages of 18-50 and in good health based on history and physical exams. Age restrictions are based on age-related declines (usually occurring after age 55-58) in eye tracking performance. Schizophrenia patients are persons with a DSM-IV Axis-I diagnosis for schizophrenia, based on a best-estimate diagnosis by the Structured Clinical Interview for DSM-IV (SCID) supplemented by family informants and medical records, done at the MPRC. Those in nicotine protocols must demonstrate that they are experienced users based upon exhaled CO and must smoke a minimum of 10 cigarettes/day with duration of use of at least 1 year. Subjects may be users of alcohol and/or marijuana but may not meet criteria for dependence on either and may not have used either for at least 24 hours prior to scanning.

Exclusion criteria

Subjects will be excluded if they are unable to undergo MRI scanning due to pregnancy, implanted metallic devices (cardiac pacemaker or neurostimulator, some artificial joints, metal pins, surgical clips or other implanted metal parts) or claustrophobia. Subjects will also be excluded if they have 1) any major medical illnesses to include, but not limited to, uncontrolled high blood pressure or high blood sugar, cardiovascular disease, asthma, peripheral vascular diseases, coagulopathies, history of superficial or deep vein thrombosis, HIV, or other infectious diseases (e.g. Hepatitis B), 2) mood or anxiety disorders, or substance-induced psychiatric disorders, 3) neurological illnesses to include, but not limited to, seizure disorders, multiple sclerosis, movement disorders, or history of head trauma, CVA, CNS tumor, and other conditions that cause neurocognitive sequelae, 4) significant alcohol or other drug use, other than nicotine dependence, 5) if their T1 weighted images reveal gross structural abnormalities and/or, 6)have a history of syncope. Urine pregnancy tests will be performed on all female volunteers of child-bearing age before each experimental session. Subjects who are positive for any drug other than nicotine or marijuana will be excluded. Subjects in nicotine protocols may not be actively seeking or engaged in smoking cessation treatment. If a subject requires change of antipsychotic medications because of exacerbation of psychotic symptoms, the subject will be considered clinically unstable and his/her participation will be discontinued. Patients with Axis-I mood disorders or substance-induced psychiatric disorders are excluded. We also exclude patients with significant alcohol or other illicit drug use, other than nicotine dependence. This is operationally defined as no SCID/DSM-IV Axis-I substance dependence in the past 6 months, and no current substance abuse. Exceptions are occasional use of marijuana.