Structural variations in the sulco-gyral pattern of the orbitofrontal cortex

Abstract

Background: The orbitofrontal cortex (OFC) is composed of sulci and gyri, which form patterns that are variations of an H-shape. Three pattern types are described with the Type III pattern associated with schizophrenia and increased risk of long-term cannabis use. No studies from Africa have described the prevalence of pattern types of the OFC. The aim of the study was to determine the sulcal and gyral patterns of the OFC in a South African sample, and whether there are any significant differences in these patterns between hemispheres and sex. Methods: A cross-sectional study of 43 embalmed adult brains was undertaken. The patterns of the sulci and gyri of the OFC were investigated, and the prevalence of each pattern type determined. Differences in the prevalence between hemispheres and sex were analyzed with Chi-square tests. Results: Type I was present in 27 hemispheres (31%), Type II in 28 (33%) and Type III in 31 (36%), with no significant differences observed between hemispheres and sex for any of the pattern types. Conclusion: The Type III pattern was found to be the most prevalent in this study. The Type III pattern may result from abnormal folding of the gyrus associated with premature birth. An increased expression of Type III has been observed in patients with an increased risk of developing schizophrenia and substance abuse disorders. Further studies are needed to investigate these associations and whether Type III can be considered as a biomarker for psychiatric disorders.

Keywords

• Orbitofrontal cortex
• Sulco-gyral pattern
• Anatomical variation
• Long-term cannabis use
• South Africa
• Schizophrenia