Anatomy and Evolution of the Parietal Lobe in Monkeys and Man

Abstract

From the evolutionary point of view the anterior and posterior parietal lobes differ from each other. The main structure of the anterior parietal lobe is the primary somatosensory cortex (SI) which consists in both monkeys and man of Brodmann’s cytoarchitectural areas 3, 1 and 2. The basic topological representation of the body also appears similar in monkeys and man. The posterior parietal lobe, however, has developed further in man than in monkeys. It consists of a superior and inferior lobule in both species. The inferior parietal lobule in particular has enlarged in humans, consisting of Brodmann’s (1907) areas 40 and 39 which have no numerical counterpart in the monkey’s brain. However, the inferior parietal lobules of monkey and human appear homologous because in von Economo’s (1929) terminology for human brain and the corresponding terminology of von Bonin and Bailey (1947) for the monkey’s brain the inferior parietal lobule consists of areas PG and PF in both species. The cytoarchitectural maps presented in Figs. 1 and 2 illustrate the views of different cytoarchitectonists. Figure 1 illustrates the human brain. In Brodmann’s terminology the anterior parietal lobe consists of areas 3, 1 and 2, whereas the posterior part consists of areas 40 and 39. The Vogts (1926) agreed with Brodmann on the anterior part of the parietal lobe distinguishing areas 3a, 3b, and a region called 1+2. The corresponding terminology of von Economo is PA (for 3a), PB (for 3b), PC (for 1), and PD (for 2) (P stands for parietal).