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Anatomy Research International
Volume 2011 (2011), Article ID 236894, 5 pages
Research Article

Mosaic Evolution of Brainstem Motor Nuclei in Catarrhine Primates

1Department of Anthropology, Dartmouth College, Hanover, NH 03755, USA
2Department of Anthropology, The George Washington University, Washington, DC 20052, USA

Received 11 February 2011; Accepted 11 April 2011

Academic Editor: Anne M. Burrows

Copyright © 2011 Seth D. Dobson and Chet C. Sherwood. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Facial motor nucleus volume coevolves with both social group size and primary visual cortex volume in catarrhine primates as part of a specialized neuroethological system for communication using facial expressions. Here, we examine whether facial nucleus volume also coevolves with functionally unrelated brainstem motor nuclei (trigeminal motor and hypoglossal) due to developmental constraints. Using phylogenetically informed multiple regression analyses of previously published brain component data, we demonstrate that facial nucleus volume is not correlated with the volume of other motor nuclei after controlling for medulla volume. Our results show that brainstem motor nuclei can evolve independently of other developmentally linked structures in association with specific behavioral ecological conditions. This finding provides additional support for the mosaic view of brain evolution.