White matter alterations in deficit schizophrenia

Schizophrenia can be classified into two separate syndromes: deficit and nondeficit. Primary, enduring negative symptoms are used to define the deficit form of the illness, which is believed to have a unique neurobiological substrate. Previous research suggests that an aberrant prefrontal-thalamic-parietal network underlies deficit schizophrenia. In this study we conducted diffusion tensor imaging (DTI) fiber tracking to assess the integrity of the superior longitudinal fasciculus (SLF), the major white matter tract that connects prefrontal and parietal cortical regions, in deficit and nondeficit people with schizophrenia. We also used proton magnetic resonance spectroscopy (1H-MRS) to assess neurochemistry in the left middle prefrontal and left inferior parietal cortical regions. A total of 20 subjects with schizophrenia (10 deficit and 10 nondeficit) and 11 healthy subjects participated in this study. Results revealed reduced fractional anisotropy (FA), an index of white matter integrity, in the right hemisphere SLF and frontal white matter in the deficit subjects. There were no differences in MRS metabolite concentrations among groups. To our knowledge, this is the first DTI study to show compromised integrity of the major white matter tract that connects frontal and parietal regions in deficit schizophrenia. These findings provide further support for altered frontal-parietal network in deficit schizophrenia.