Scientific Abstract

Background

Insula is a key cortical region with extensive cortico-limbic connections, and hypothesized to play a multifaceted role in various processes and in interoception. Morphological irregularities in this region may contribute to schizophrenia (SZ), schizoaffective disorder (SAD), and psychotic bipolar disorder (BDP) symptomatology. Previous studies of insula have led to somewhat inconsistent resu lts. This study aims to utilize a large sample of SZ, SAD and BDP to examine the both the right and left insula and their anterior and posterior components of across psychoses.

Methods

T1-MPRAGE scans were obtained using 3T scanners. Insula measurement were extracted using FreeSurfer (FS) 7.1 in healthy controls (HC=935) and psychosis probands (SZ=481, SAD=383, BDP=381). FS measures were correlated with cognitive measures and symptomatology, in SZ/SAD/BPD. P values < 0.05 adjusted for FDR were reported.

Results

Volume. Proband versus HC comparisons showed the volume of the L and R insula was greater in the HCs. No between patient group findings. Proband versus HC comparisons, showed that bilateral anterior insula volume was greater in the HCs, except for the SZ-HC group, which had larger bilateral posterior volume.

Cortical Thickness (CT). SZ and SAD versus HC comparisons showed bilateral anterior insula was greater in the HCs. BDP was found to have greater CT than SAD.

Local Gyrification Index (LGI). SAD versus HC comparisons showed bilateral anterior insula was greater in the HCs.

No significant correlations were seen between insula and symptomatology.

Bilateral A/P tests for cognition yielded positive correlations mainly in anterior volume for SZ and anterior LGI for both SAD and BDP.

Conclusions

Our observations suggest structural alterations in the insula across affective and non-affective psychotic disorders. Though we observed relations between insula and cognitive measures, we did not see correlations with symptomatology. Future studies need to further examine the relation between insular structure and socio-emotional and self-processing thought to be related to anterior insula.