Interstitial cells of the white matter in the inferior parietal cortex in schizophrenia: An unbiased cell-counting study.

Previous studies have found an increased density of the interstitial cells of the white matter (ICWMs) in the frontal and temporal cortex in schizophrenia. Some data suggested this abnormality was restricted to a subgroup of patients, whose clinical features were consistent with the presence of the deficit syndrome. Clinical studies suggest deficit features are due to an abnormality in a cortical-subcortical circuit that includes dorsolateral prefrontal and inferior parietal cortex. We compared the density of ICWMs labeled for MAP2 immunoreactivity in Brodmann area 39 (inferior parietal cortex) from nine schizophrenia subjects (three deficit and six nondeficit) and nine matched controls using an unbiased cell-counting technique. The density of ICWMs was significantly greater in the deficit syndrome subjects compared to the nondeficit schizophrenia group (respective means +/- SEM, 0.22 +/- 0.04, and 0. 13 +/- 0.02; P < 0.05). The density of ICWMs in the deficit group was also significantly greater (P < 0.05) than that of the control group (0.09 +/- 0.02), but the nondeficit and control groups were not significantly different. These findings 1) confirm that an abnormal placement of neurons in the white matter is found in schizophrenia, 2) provide evidence for a microscopic anatomical abnormality in the inferior parietal cortex, and 3) suggest the ICWM abnormality may be confined to deficit patients.