Liability Markers for Deficit Schizophrenia?

University Of Maryland Baltimore, Baltimore MD

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Abstract

[unreadable] DESCRIPTION (provided by applicant): The heterogeneity theory of schizophrenia is generally accepted but identification of subtypes, which is crucial for genetic research, has been difficult. Deficit syndrome schizophrenia has been proposed as a valid subtype and is characterized by patients who exhibit primary enduring negative symptoms. High concordance of deficit schizophrenia in families suggests a shared genetic and/or environmental etiology. This proposed study represents the first effort (to our knowledge) to systematically determine neurobiological markers for deficit schizophrenia by studying their non-psychotic family members. Non-ill relatives may carry smaller numbers of susceptibility genes that do not result in psychosis, but may result in abnormalities that can be detected by neurobiological tests such as eye movements. Identification of heritable cognitive and electrophysiological abnormalities in deficit syndrome will help demarcate the boundary of the disorder and provide alternative phenotypes in genetic studies. Neurobiological abnormalities identified only in deficit patients and their family members may be marking the liability of deficit schizophrenia. In our preliminary study with small sample sizes that examined components of the smooth pursuit eye movement response, we found that impaired smooth pursuit initiation was specifically associated with deficit probands and their relatives, whereas predictive smooth pursuit was equally impaired in patients with and without deficit schizophrenia and in their relatives. This supports the validity of our research approach. In this proposed study, we aim to determine whether pursuit initiation is impaired only in relatives of deficit probands by using a modified initiation task in which predictive factors are minimized. We will also include memory saccade task, antisaccade tasks, and a version of the CPT with degraded presentations. These tasks are chosen because they have shown evidence of association with schizophrenia or deficit syndrome. These tasks will be administered to 30 relatives of deficit probands, 30 relatives of nondeficit probands, and 30 normal controls. Testing in relatives rather than patients will serve to eliminate differences in secondary effects of psychosis and medications. We plan to use the preliminary data collected from this grant support to guide our full-scale search for phenotypic markers specifically associated with the liability for deficit schizophrenia and subsequent molecular genetic studies. [unreadable] [unreadable]