Comparative lateralisation patterns in the language area of human, chimpanzee, and rhesus monkey brains.

Lateralised architectural differences in radial cell column structure were detected in the planum temporale of humans but were not found in homologous regions of ape or monkey brains. This study used a new computer imaging method to quantify the architecture of thousands of cortical minicolumns. A study of Lamina III in the left hemisphere of human brains revealed a wider separation between cell columns and more non-neuronal (empty) space within cell columns compared to the right hemisphere. This asymmetry was absent in the chimpanzee brains and weakly reversed in the rhesus monkey brains. The results imply an evolution towards more clearly defined columnar structures in the left hemisphere of human brains compared to those of monkeys.