No correlations are found between the increased fALFF values and clinical variables in the patients. There are also no correlations between the increased fALFF values and age or years of education.
Several limitations should be addressed when interpreting the present results. First, the present study focuses on the DMN. It enhances the specificity of the findings from the DMN. For the same reason, the results from other brain regions have been neglected. Second, a trend level of significance of group differences in years of education is observed in the present study. It is understandable that the patients receive less years of education than the controls. The effects of unmatched education level may not be completely eliminated, although this variable is used as a covariate in the group comparisons. Finally, the sample size is relatively small. Large sample size is needed to elucidate the subtle changes of brain activity and FC in schizophrenia.
Despite the limitations, the present study observes hyperactivity of the DMN in first-episode, drug-naive patients with paranoid schizophrenia revealed by the family-based case–control and traditional case–control designs, which highlights the importance of the DMN in the neurobiology of schizophrenia. Family-based case–control design can limit the confounding effects of environmental factors in schizophrenia. Combination of the family-based case–control and traditional case–control designs may be a viable option for the neuroimaging studies to examine the abnormalities specified to the disease in schizophrenia and the trait alterations shared by the patients and the FBC.
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