Cortical gyrification and its relationships with cortical volume, cortical thickness, and cognitive performance in healthy mid-life adults.

Across species, greater cortical gyrification, or folding of the cortex, has been shown to be associated with higher cognitive abilities and is thought to reflect an evolutionary process aimed at maximizing the number of cerebral computational units while minimizing the energy and communication costs of larger brains. Relatively little is known about the significance of individual variation in gyrification in humans and how it relates to other aspects of cerebral structure and function. In the current study, we examined relationships between cortical gyrification and (i) cortical volume, (ii) cortical thickness, and (iii) executive functions. Participants were middle-aged healthy adults (44-48 years old, n=396) in a community-based sample. T1-weighted 3D structural magnetic resonance imaging scans were acquired in a Fast Field Echo sequence. Cortical gyrification, volume, and thickness were measured through the semi-automated software FreeSurfer. Results showed that cortical gyrification was strongly and positively related to cortical volume, but was negatively related to cortical thickness in many regions of the cortex. In addition, frontal gyrification was positively related to performance in working memory and mental flexibility tasks. These results support the view that greater cortical gyrification is related both to bigger brain volumes and better cognitive function, but not to greater cortical thickness. The results provide evidence of functional relevance of cortical gyrification development, and show that it can be a useful index to investigate structure-cognition relationships.