# Corrigendum: Brain scaling in mammalian evolution as a consequence of concerted and mosaic changes in numbers of neurons and average neuronal cell size

^{1}Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil^{2}Instituto Nacional de Neurociência Translacional, Ministério de Ciência e Tecnologia, São Paulo, Brazil^{3}Department of Anatomy, University of the Witwatersrand, Johannesburg, South Africa^{4}Department of Psychology, Vanderbilt University, Nashville, TN, USA

A Corrigendum on

Brain scaling in mammalian evolution as a consequence of concerted and mosaic changes in numbers of neurons and average neuronal cell size

*by Herculano-Houzel, S., Manger, P. R., and Kaas, J. H. (2014). Front. Neuroanat. 8:77. doi: 10.3389/fnana.2014.00077*

It has come to our attention that some of the data on the cellular composition of the brain of artiodactyls, presented in Table 1 of Kazu et al. (2014) and used in this review, needed minor corrections, which were published in a Corrigendum to that paper.

While those corrections do not at all modify the conclusions of the present paper, some of the power exponents reported here were influenced in minor, non-significant ways. We provide those corrected power exponents below.

p. 4, Figure 2, top right—The mass of each brain structure varies as a similar, shared power function of the number of non-neuronal (other) cells in the structure of exponent 1.050 ± 0.018 (*p* < 0.0001).

p. 6, Figure 3, top: Mass of the cerebral cortex increases with number of neurons raised to an exponent of 1.694 ± 0.048 across non-primates.

p. 6, Figure 3, bottom: Neuronal density in the cerebral cortex decreases with number of neurons raised to an exponent of −0.693 ± 0.048 (*p* < 0.0001).

p. 9, Figure 4: In non-primates, non-eulipotyphlans, cerebellar mass increases with number of neurons raised to an exponent of 1.283 ± 0.035 (*p* < 0.0001) and cerebellar neuronal density scales with number of neurons raised to an exponent of −0.282 ± 0.035 (*p* < 0.0001).

Figure 7:

A—Neuronal density in the cerebral cortex scales with neuronal density in the rest of brain raised to an exponent of 0.876 ± 0.041, *p* < 0.0001 (excludes primates).

B—Neuronal density in the cerebellum scales with neuronal density in the rest of brain raised to an exponent of 0.442 ± 0.049, *p* < 0.0001 (excludes primates and eulipotyphlans).

C—Neuronal density in the olfactory bulb scales with neuronal density in the rest of brain raised to an exponent of 0.994 ± 0.118, *p* < 0.0001 (excludes primates and eulipotyphlans).

D—Neuronal density in the olfactory bulb scales with neuronal density in the cerebral cortex raised to an exponent of 1.139 ± 0.113, *p* < 0.0001 (excludes primates and eulipotyphlans).

E—Neuronal density in the cerebellum scales with neuronal density in the cerebral cortex raised to an exponent of 0.516 ± 0.041, *p* < 0.0001 (excludes primates and eulipotyphlans).

F—Neuronal density in the olfactory bulb scales with neuronal density in the cerebellum raised to an exponent of 1.706 ± 0.161, *p* < 0.0001 (includes all clades).

p. 12, Figure 8A—Artiodactyls gain neurons in the cerebral cortex faster than they gain neurons in the rest of brain, as a power function of exponent 1.552 ± 0.056, *p* = 0.0013, *r*^{2} = 0.997 (excludes the giraffe).

p. 12, Figure 8B—Artiodactyls gain neurons in the cerebellum faster than they gain neurons in the rest of brain, as a power function of exponent 1.737 ± 0.304, *p* = 0.0107, *r*^{2} = 0.916.

p. 14, Figure 9B—The number of neurons in the cerebellum varies as a power function of the number of neurons in the cerebral cortex with an exponent of 0.922 ± 0.110, *p* = 0.0036, across artiodactyls. The relationship for the ensemble of clades can also be fit with a linear function of slope 4.16 (*p* < 0.0001, *r*^{2} = 0.985).

p. 15, Figure 10A—Artiodactyls have on average 7.35 ± 1.24 neurons in the cerebral cortex to every neuron in the rest of brain. This ratio increases as a power function of the number of neurons in the rest of brain with an exponent of 0.904 ± 0.132 (*p* = 0.0135, *r*^{2} = 0.902).

p. 16, Figure 10B—Artiodactyls have a ratio between numbers of neurons in the cerebellum and in the rest of brain of 38.32 ± 6.19.

p. 17—Artiodactyls have an average ratio of neurons in the cerebellum relative to the cerebral cortex of 5.28 ± 0.31.

p. 21, Figure 13:

A—The mass of the cerebral cortex increases across non-primates with the mass of the rest of brain raised to an exponent of 1.155 ± 0.027, *p* < 0.0001.

B—The mass of the cerebellum increases across non-primates with the mass of the rest of brain raised to an exponent of 1.054 ± 0.019, *p* < 0.0001.

C—The mass of the olfactory bulb increases across non-primates with the mass of the rest of brain raised to an exponent of 0.812 ± 0.043, *p* < 0.0001.

D—The relative mass of the cerebral cortex increases across all species in correlation with brain mass with a Spearman correlation *r*^{2} = 0.7840, *p* < 0.0001.

E—The relative mass of the cerebellum varies across all species in correlation with brain mass with a Spearman correlation *r*^{2} = −0.5270, *p* = 0.0008.

F—The relative mass of the rest of brain varies across all species in correlation with brain mass with a Spearman correlation *r*^{2} = −0.7994, *p* < 0.0001.

p. 21, Figure 14—The cerebral cortex of artiodactyls gains mass as a function of the number of neurons in the rest of brain with exponent 2.759 ± 0.145, *p* = 0.0028. The cerebellum of artiodactyls gains mass as a function of the number of neurons in the rest of brain with exponent 2.142 ± 0.492, *p* = 0.0489.

p. 24, Figure S17—In artiodactyls, cerebral cortical mass increases as a power function of body mass with exponent 0.589 ± 0.028, *p* = 0.0023; rest of brain mass increases as a power function of body mass with exponent 0.378 ± 0.056, *p* = 0.0215; the number of neurons in the cerebral cortex scales with body mass raised to an exponent of 0.454 ± 0.107, *p* = 0.0511; and the number of neurons in the rest of brain scales with body mass raised to an exponent of 0.227 ± 0.027, *p* = 0.0136.

## Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest

Keywords: brain evolution, number of neurons, cell size, number of glial cells, glia-neuron ratio

Citation: Herculano-Houzel S, Manger PR and Kaas JH (2015) Corrigendum: Brain scaling in mammalian evolution as a consequence of concerted and mosaic changes in numbers of neurons and average neuronal cell size. *Front. Neuroanat*. **9**:38. doi: 10.3389/fnana.2015.00038

Received: 02 March 2015; Accepted: 12 March 2015;

Published: 26 March 2015.

**Edited and reviewed by:** Patrick R. Hof, Icahn School of Medicine at Mount Sinai, USA

Copyright © 2015 Herculano-Houzel, Manger and Kaas. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Suzana Herculano-Houzel, suzanahh@gmail.com