Elucidating neuroanatomical alterations in the at risk mental state and first episode psychosis: a combined voxel-based morphometry and voxel-based cortical thickness study

Abstract

Previous studies have reported alterations in grey matter volume and cortical thickness in individuals at high risk of developing psychosis and patients in the early stages of the disorder. Because these studies have typically focused on either grey matter volume or cortical thickness separately, the relationship between these two types of alterations is currently unclear. In the present investigation we used both voxel-based cortical thickness (VBCT) and voxel-based morphometry (VBM) to examine neuroanatomical differences in 21 individuals with an At Risk Mental State (ARMS) for psychosis, 26 patients with a First Episode of Psychosis (FEP) and 24 healthy controls. Statistical inferences were made at P<0.05 after correction for multiple comparisons. Cortical thinning in the right superior temporal gyrus was observed in both individuals at high risk of developing psychosis and patients with a first episode of the disorder, and therefore is likely to represent a marker of vulnerability. In contrast, the right posterior cingulate cortex showed cortical thinning in FEP patients relative to individuals at high risk, and therefore appears to be implicated in the onset of the disease. These neuroanatomical differences were expressed in terms of cortical thickness but not in terms of grey matter volume, and therefore may reflect specific cortical atrophy as opposed to variations in sulcal and gyral morphology.

Keywords: At Risk Mental State; Cortical thickness; First Episode Psychosis; Imaging; VBM.

Fig. 1

Left. Brain regions showing cortical thinning in both ARMS and FEP participants compared to healthy controls (P < 0.001uncorrected, for display purposes). T-scores are shown in the coloured bar. Right. Cortical thickness (CT) estimates in the right superior temporal cortex are shown for the three groups with the dashed lines indicating group CT means. Cortical thickness is measured in terms of mm between the inner and outer surfaces of grey matter.

Fig. 2

Left. Brain regions showing cortical thinning in FEP patients compared to ARMS participants (P < 0.001 uncorrected, for display purposes). T-scores are shown in the coloured map. Right. Cortical thickness (CT) estimates in the right posterior cingulate cortex are shown for the three groups with the dashed lines indicating group CT means. Cortical thickness is measured in terms of mm between the inner and outer surfaces of grey matter.