Sulcogyral pattern and sulcal count of the orbitofrontal cortex in individuals at ultra high risk for psychosis

Abstract

Three types of orbitofrontal cortex (OFC) sulcogyral patterns have been identified in the general population. The distribution of these three types has been found to be altered in individuals at genetic risk of psychosis, and in patients with first episode psychosis (FEP) and chronic schizophrenia. This study aims at establishing whether altered OFC sulcogyral patterns were present in a large cohort of individuals at ultra high risk (UHR) for psychosis. OFC pattern type was classified and the number of posterior and intermediate sulci present on the surface of the OFC was counted. OFC sulcogyral type and the number of sulci were compared between controls (n=58) and UHR participants who transitioned (n=49) versus those who did not transition (n=77) to psychosis. Finally, the relationship between sulcogyral type and number of sulci with intellectual quotient (IQ), symptom severity and social functioning of UHR individuals was explored. In line with other studies conducted in chronic schizophrenia and FEP, UHR individuals who later transitioned to psychosis showed a reduced incidence of the Type I OFC on the right hemisphere compared to controls (χ(2)=19.847, p<0.001). These highly consistent results point towards the protective effect of possessing a Type I OFC in the right hemisphere. Furthermore, OFC sulcus counts revealed that controls presented with a higher number of posterior (right hemisphere; χ(2)=11.658, p=0.003) and intermediate sulci (left: χ(2)=6.643, p=0.036; right: χ(2)=11.726, p=0.020) when compared to UHR individuals. However, no associations between OFC types or sulcus count and IQ, symptoms and functioning were observed.

Keywords: Gyrification; Orbit-frontal cortex; Psychosis; Social functioning; Sulci; Symptom severity; Ultra high risk.