Vertex- and atlas-based comparisons in measures of cortical thickness, gyrification and white matter volume between humans and chimpanzees

Abstract

What changes in cortical organisation characterise global and localised variation between humans and chimpanzees remains a topic of considerable interest in evolutionary neuroscience. Here, we examined regional variation in cortical thickness, gyrification and white matter in samples of human and chimpanzee brains. Both species were MRI scanned on the same platform using identical procedures. The images were processed and segmented by FSL and FreeSurfer and the relative changes in cortical thickness, gyrification and white matter across the entire cortex were compared between species. In general, relative to chimpanzees, humans had significantly greater gyrification and significantly thinner cortex, particularly in the frontal lobe. Human brains also had disproportionately higher white matter volumes in the frontal lobe, particularly in prefrontal regions. Collectively, the findings suggest that after the split from the common ancestor, white matter expansion and subsequently increasing gyrification occurred in the frontal lobe possibly due to increased selection for human cognitive and motor specialisations.

A core speech circuit between primary motor, somatosensory, and auditory cortex: evidence from connectivity and genetic descriptions

“…In monkeys, stimulating the mid/caudal lateral belt, adjacent to primary auditory cortex, produces strong activation of the CS (Petkov et al, 2015) . Furthermore, it seems that humans have significantly thicker and more gyrification in the CS and TTG than chimpanzees (Hopkins, Li, Crow, & Roberts, 2016) . Human CS and TTG are the most highly myelinated regions in the human brain (Carey, Krishnan, Callaghan, Sereno, & Dick, 2017;Lutti, Dick, Sereno, & Weiskopf, 2014) and may be connected by white matter tracts (Fan et al, 2016) .…”

Human-specific genomic signatures of neocortical expansion

“…Yet, a locally greater gyrification in modern humans compared to chimpanzees is particularly evident in the frontal lobe [6]. Moreover, the variability in cortical folding among human individuals is greater in the most anterior, prefrontal areas than in posterior areas of the frontal lobe [7].…”

Automatic analysis of cross‐sectional cerebral asymmetry on 3D in vivo MRI scans of human and chimpanzee

“…All MRI scans were pre‐processed in FSL (://sl.fmrib.ox.ac.uk/fsl/fslwiki/) including skull strip, bias field correction, and brain normalization to the MNI152 template using 7 degrees of freedom (DoF) transformations (i.e., 3 translations, 3 rotations, and 1 uniform scaling). Details of the processes are described elsewhere (Hopkins, Li, Crow, & Roberts, ). The 7 DoF transformation is particularly important to normalize the chimpanzee brain to the size of the human brain to enable to subsequent processing in the standard FreeSurfer processing stream that is designed for the human brain (://surfer.nmr.mgh.harvard.edu/).…”

“…Details of the processes are described elsewhere (Hopkins, Li, Crow, & Roberts, 2016). The 7 DoF transformation is particularly important to normalize the chimpanzee brain to the size of the human brain to enable to subsequent processing in the standard FreeSurfer processing stream that is designed for the human brain (https://surfer.nmr.mgh.harvard.…”