Brain Size and Folding of the Human Cerebral Cortex

Abstract

During evolution, the mammalian cerebral cortex has expanded disproportionately to brain volume. As a consequence, most mammals with large brains have profusely convoluted cortices. The human cortex is a good example of this trend, however, given the large variability in human brain size, it is not clear how cortical folding varies from the smallest to the largest brains. We analyzed cortical folding in a large cohort of human subjects exhibiting a 1.7-fold variation in brain volume. We show that the same disproportionate increase of cortical surface relative to brain volume observed across species can be also observed across human brains: the largest brains can have up to 20% more surface than a scaled-up small brain. We introduce next a novel local measure of cortical folding, and we show that the correlation between cortical folding and size varies along a rostro-caudal gradient, being especially significant in the prefrontal cortex. The expansion of the cerebral cortex, and in particular that of its prefrontal region, is a major evolutionary landmark in the emergence of human cognition. Our results suggest that this may be, at least in part, a natural outcome of increasing brain size.

Gender Differences in Cerebral Cortical Folding: Multivariate Complexity-Shape Analysis with Insights into Handling Brain-Volume Differences

“…It shows that handling ICV differences in folding studies may not be as simple as including ICV as a covariate in the underlying statistical test. This paper proposes two systematic methods for handling ICV changes in folding studies using the proposed descriptor and shows that while the findings using one method are consistent with [10], those using the other method are consistent with [11,12].…”

“…Moreover, while one study [10] using the fractal-dimension (FD) measure reported higher complexity in adult females, two very recent studies [11,12] using the isoperimetric ratio (IPR) measure report higher complexity in larger adult brains (i.e. males).…”

“…Convexity ratio (CR) [6] is the ratio of the area of the surface to the area of the convex hull/envelope of the surface. IPR [6,11,12] is the ratio of the surface area to the two-third power of the volume enclosed by the surface. Average curvedness (AC) [8] measures the deviation of the surface from a plane.…”

How the flow and processing of information shapes the cerebrum

“…Such a data set of human subjects (Pausova et al, 2007) was analyzed by Toro et al (2008). These data (314 subjects, 164 females and 150 males of 12-20 years old) are presented in Figure 1c.…”

“…Judging from the human data ( Fig. 1d) and taking 290 the data of (Toro et al, 2008) as a reference, it seems that systematic errors may be considerable, depending on the author. The sphericity parameter, s had a standard deviation (SD) of 0.09.…”