The neural basis of deficits in acquisition and extinction of fear in schizophren

Massachusetts General Hospital, Boston MA

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Abstract

DESCRIPTION (provided by applicant): People who develop schizophrenia show deficits in emotional learning and memory, which have been linked to the symptoms of the disorder. Yet the neurobiological basis of these deficits is unknown. One challenging issue associated with this question is that the medications used to treat schizophrenia also cause some impairment in emotional function, so it has been difficult in previous studies to distinguish effects of the disorder from those of the medications used by the majority of the patients with the illness. One common method used to study emotional learning and memory in mammals, including humans, is called Pavlovian fear conditioning. In Pavlovian fear conditioning procedures, a person is exposed to a neutral stimulus, such as a tone or picture, which is followed by an unpleasant sensation, such as a loud noise or mild electrical stimulus. After a certain number of repetitions of this procedure, the person begins to experience some anticipatory anxiety or fear when exposed to the neutral stimulus by itself. A second type of learning can occur when this neutral stimulus is later presented several times without being followed by the unpleasant stimulus; this is called extinction learning and it requires the formation of a memory trace that is coded separately from the fear memory. These fear and extinction memories can be recalled at a later time, depending on the circumstances (called the context) during the formation and recall of the memories. We have found evidence suggesting that the learning and later recall of fear and extinction memories is abnormal in schizophrenia. In this project, we will test the hypothesis that these abnormalities in fear and extinction learning and memory in schizophrenia are related to specific changes in the function of the brain regions known to drive these processes, and that these neural changes are linked to specific symptoms of schizophrenia. We will also determine whether any of the abnormalities in this system arise from, are worsened or improved by treatment with antipsychotic medications. This project has implications for understanding the fundamental pathophysiology of schizophrenia and for developing early markers and new treatments for the disorder.