Cellular scaling rules for primate brains

doi:10.1073/pnas.0611396104

Cellular scaling rules for primate brains

^†Department of Psychology, Vanderbilt University, Nashville, TN 37203; and
*Departamento de Anatomia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, 21941-590, Rio de Janeiro, Brazil

Contributed by Jon H. Kaas, December 28, 2006 (received for review December 11, 2006)

Abstract

Primates are usually found to have richer behavioral repertoires and better cognitive abilities than rodents of similar brain size. This finding raises the possibility that primate brains differ from rodent brains in their cellular composition. Here we examine the cellular scaling rules for primate brains and show that brain size increases approximately isometrically as a function of cell numbers, such that an 11× larger brain is built with 10× more neurons and ≈12× more nonneuronal cells of relatively constant average size. This isometric function is in contrast to rodent brains, which increase faster in size than in numbers of neurons. As a consequence of the linear cellular scaling rules, primate brains have a larger number of neurons than rodent brains of similar size, presumably endowing them with greater computational power and cognitive abilities.

Footnotes

^‡To whom correspondence should be addressed at:
Vanderbilt University, 111 21st Avenue South, Nashville, TN 37203.
E-mail: jon.h.kaas{at}vanderbilt.edu
Author contributions: S.H.-H., C.E.C., P.W., and J.H.K. designed research; S.H.-H., C.E.C., and P.W. performed research; S.H.-H. analyzed data; and S.H.-H. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/cgi/content/full/0611396104/DC1.
Abbreviations:

MBR,

brain mass;

MBO,

body mass;

MCX,

mass of cerebral cortex;

MCB,

mass of the cerebellum;

MRE,

mass of remaining structures;

MN,

average mass of neuronal cells;

MNN,

average mass of nonneuronal cells;

NN,

number of neurons;

NNN,

number of nonneuronal cells;

NNcx,

number of neurons in the cerebral cortex;

NNcb,

number of neurons in the cerebellum;

NNre,

number of neurons in the remaining areas.