Present address: Max Planck Institute for Biological Cybernetics, Tubingen, Germany.
How many neurons do you have? Some dogmas of quantitative neuroscience under revision
Article first published online: 13 DEC 2011
© 2011 The Authors. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd
European Journal of Neuroscience
Volume 35, Issue 1, pages 1–9, January 2012
How to Cite
Lent, R., Azevedo, F. A. C., Andrade-Moraes, C. H. and Pinto, A. V. O. (2012), How many neurons do you have? Some dogmas of quantitative neuroscience under revision. European Journal of Neuroscience, 35: 1–9. doi: 10.1111/j.1460-9568.2011.07923.x
- Issue published online: 2 JAN 2012
- Article first published online: 13 DEC 2011
- Received 22 May 2011, revised 18 September 2011, accepted 27 September 2011
- brain development;
- brain evolution;
- glial cell number;
- neuron number
Owing to methodological shortcomings and a certain conservatism that consolidates wrong assumptions in the literature, some dogmas have become established and reproduced in papers and textbooks, derived from quantitative features of the brain. The first dogma states that the cerebral cortex is the pinnacle of brain evolution – based on the observations that its volume is greater in more ‘intelligent’ species, and that cortical surface area grows more than any other brain region, to reach the largest proportion in higher primates and humans. The second dogma claims that the human brain contains 100 billion neurons, plus 10-fold more glial cells. These round numbers have become widely adopted, although data provided by different authors have led to a broad range of 75–125 billion neurons in the whole brain. The third dogma derives from the second, and states that our brain is structurally special, an outlier as compared with other primates. Being so large and convoluted, it is a special construct of nature, unrelated to evolutionary scaling. Finally, the fourth dogma appeared as a tentative explanation for the considerable growth of the brain throughout development and evolution – being modular in structure, the brain (and particularly the cerebral cortex) grows by tangential addition of modules that are uniform in neuronal composition. In this review, we sought to examine and challenge these four dogmas, and propose other interpretations or simply their replacement with alternative views.