Cerebral Cortex Advance Access published online on February 10, 2008
Cerebral Cortex, doi:10.1093/cercor/bhm261
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Brain Size and Folding of the Human Cerebral Cortex
Paus1,41 Brain & Body Centre, University of Nottingham, Nottingham NG7 2RD, United Kingdom, 2 CEGEP Jonquiere, Jonquiere, Quebec G7X 7W2, Canada, 3 University of Montreal, Montreal, Quebec H3C 3J7, Canada, 4 Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2T5, Canada, 5 University of Quebec in Chicoutimi, Chicoutimi, Quebec G0V 1L0, Canada
Address correspondence to Roberto Toro, PhD, Brain & Body Centre, University of Nottingham, Nottingham, United Kingdom. Email: rto{at}psychology.nottingham.ac.uk.
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.
Key Words: brain size • cortical folding • development • evolution