Morphological development of human hippocampus: cross-sectional and longitudinal studies by high-resolutionmagnetic resonance imaging

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Morphological development of human hippocampus and related brain regions and its implications in the pathophysiology of schizophrenia were investigated using magnetic resonance imaging (MRI).1. Volumes of the hippocampus and the amygdala were significantly larger in male elder adolescents than in male younger adolescents. These results suggest a robust maturational process ongoing in the human hippocampus and amygdala during adolescence, especially in males, which maybe relevant to progress in myelination.2. Volumetric analyses demonstrated that, in patients with schizotypal disorder, volumes of the amygdala and hippocampus were significantly reduced, whereas prefrontal volumes were preserved. Shizophrenia patients had significant volume reductions in the prefrontal areas as well as in the amygdala and hippocampus. These findings suggest that volume reductions in the amygdala and hippocampus may represent the vulnerability, whereas additional widespread involvement of the prefrontal cortex in schizophrenia may play critical roles in the manifestation of overt psychosis.3. Structural abnormalities in the cerebral midline structures such as the cavum septi pellucidi (CSP) and the adhesio interthalamica (AI), and their relation with the volumes of the medial temporal structures were explored in schizophrenia patients. The patients with a large CSP had smaller volumes of bilateral amygdala and left posterior parahippocampal gyrus than those without it. The patients without an AI had a smaller bilateral amygdala than those with an AL These findings suggest that the abnormalities in the cerebral midline structures and the medial temporal lobe regions may reflect developmental disturbance in the neural network including the midline and associated limbic structures of the brain in schizophrenia.