Relative Size of the Anterior Thalamic Nuclei Differentiates Anthropoids by Social System

Abstract
Anthropoid primates differ in the sizes of their limbic nuclei. Morphometric analyses of the anterior principal thalamic nucleus and the medial mamillary nuclei reveal that both regions increase in size as a function of brain weight. However, after controlling for the size of the brain anthropoids classified as having single-male societies have more anterior principal thalamic neurons than do primates that are classified as multi-male. The relative sizes of the mammillary nuclei do not show this clustering. The differences in the size of the anterior nucleus are hypothesized to be specific for this nucleus and not the result of a general limbic or of heterochronic changes.