Abstract
In this study, we investigated and quantified the amygdalar and hippocampal morphometry abnormalities exerted by first-episode schizophrenia using a total of 92 patients and 106 healthy control participants. Magnetic resonance imaging (MRI) based automated segmentation was conducted to obtain the amygdalar and hippocampal segmentations. Disease-versus-control volume differences of the bilateral amygdalas and hippocampi were quantified. In addition, deformation-based statistical shape analysis was employed to quantify the region-specific shape abnormalities of each structure of interest. To better identify the key relevant areas in the pathology of first-episode schizophrenia, each structure was divided into four subregions; CA1, CA2, CA3 combined with dentate gyrus for the hippocampus in each hemisphere and basolateral, basomedial, centromedial, and lateral nucleus for the amygdala in each hemisphere. We observed significant global volume reduction and localized shape atrophy in each of the four structures of interest. The amygdalar shape abnormalities mainly occurred at the basolateral and centromedial subregions, whereas the hippocampal shape abnormalities mainly concentrated on the CA1 and CA2 subregions. For the same structure, the one on the right hemisphere was affected more by the disease pathology than that on the left hemisphere. To conclude, we have successfully quantified the global and local morphometric abnormalities of the bilateral amygdalas and hippocampi using a sophisticated statistical analysis pipeline and high-field subregion segmentations, with MRI data of a considerable sample size. This study is one of the very first of such kind in first-episode schizophrenia analyses.
Highlights
Schizophrenia is a chronic mental disorder characterized by positive symptoms such as distorted perception and delusional beliefs, negative symptoms such as flattened affect and social withdrawal, as well as cognitive impairments such as deficits in working memory, attention, problem solving, processing speed, and social cognition [1]
We investigated first-episode schizophrenia (FES) related morphometric abnormalities of the amygdala and the hippocampus in both hemispheres in a coarse-to-fine manner; both global volume and localized shape morphometric abnormalities were quantified based on the structural MR images of 92 FES patients and 106 healthy control (HC)
The degrees of volume reductions were similar across structures, with the z-score differences being around −0.3
Summary
Schizophrenia is a chronic mental disorder characterized by positive symptoms such as distorted perception and delusional beliefs, negative symptoms such as flattened affect and social withdrawal, as well as cognitive impairments such as deficits in working memory, attention, problem solving, processing speed, and social cognition [1]. Some studies reported volumetric reductions of the bilateral amygdalas in FES [3, 8, 9, 13] whereas some other studies reported no significant amygdalar volume changes when comparing FES patients to matched healthy control (HC) participants [6, 12] This type of conflicting findings occur to the hippocampus as well, the structure which has been investigated more extensively than the amygdala in FES literature; some MRI studies observed no significant FES related hippocampal volume abnormalities [8, 10, 12, 13] even though a majority of existing studies have identified hippocampal volume atrophies in FES patients [5,6,7, 11]
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