2006.Glia.Marino.comment.PNAS

COMMENTARYAbsolutebrainsize:Didwethrowthebabyoutwiththebathwater?Lori Marino*Neuroscience and Behavioral Biology Program, 1462 Clifton Road, Suite 304, Emory University, Atlanta, GA 30322he recent study by Sherwood et species’ brain is devoted to cognitive dicted by the allometric scaling inherental. (1) in this issue of PNAS is processes. But could we have, at the in the enlargement of the human brain.a study in irony. It is thus so very least, missed something important In other words, Sherwood et al. (1) showTbecause the authors used some about absolute brain size in the process? that overall or absolute brain size con-of the most current and sophisticated Did we throw the baby out with the stitutes a key factor in the ratio of gliahistological and data-analytic tools to, in bathwater? The Sherwood et al. (1) to neurons. The authors suggest that thethe end, unearth...adinosaur. Now the study suggests that we might have. greater numbers of glia in the humanauthors did not do this in the literal Recent microarray studies have shown neocortex may be due to the increasedsense. Rather, they laid bare an ‘‘ex- that neuronal signaling and energy pro- energetic costs of larger dendritic arborstinct’’ measure of brain anatomy: that duction genes are up-regulated in the and longer fiber projections within theold fossil known as absolute brain size. human neocortex compared with the context of the large human brain. TheEven as far back as the 1800s, Alex- great ...