Context: Whether psychoses associated with schizophrenia and affective disorder represent manifestations of different disorders or the same disorder is an important but unresolved question in psychiatry. Results of previous volumetric magnetic resonance imaging investigations indicate that gray matter volume reductions in neocortical regions may be specific to schizophrenia. Objective: To simultaneously evaluate multiple olfactocentric paralimbic regions, which play crucial roles in human emotion and motivation, in first-episode patients with schizophrenia and affective psychosis. Design: A cross-sectional study using high-spatial resolution magnetic resonance imaging in patients with schizophrenia and affective psychosis at their first hospitalization. Setting: Inpatient units at a private psychiatric hospital. Participants: Fifty-three first-episode patients, 27 with schizophrenia and 26 with affective (mainly manic) psychosis, and 29 control subjects. Main Outcome Measures: Using high-spatial resolution magnetic resonance imaging, the gray matter volumes of 2 olfactocentric paralimbic regions of interest, the insular cortex and the temporal pole, were evaluated. Results: A bilateral volume reduction in insular cortex gray matter was specific to first-episode patients with schizophrenia. In contrast, both first-episode psychosis groups showed a volume reduction in left temporal pole gray matter and an absence of normal left-greater-than-right asymmetry. Region of interest correlations showed that only patients with schizophrenia lacked a positive correlation between left temporal pole and left anterior amygdalahippocampal complex gray matter volumes, whereas both psychosis groups were similar in lacking normal positive correlations between left temporal pole and left anterior superior temporal gyrus gray matter volumes. Conclusions: These partially different and partially similar patterns of structural abnormalities in olfactocentric paralimbic regions and their associated abnormalities in other temporolimbic regions may be important factors in the differential and common manifestations of the 2 psychoses.
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