A Comparative Study of the Superior Olivary Complex in the Primate Brain

The superior olivary complex is a brainstem auditory center which exhibits differential development of its component nuclei in primates. The nucleus of the trapezoid body and the lateral olivary nucleus are similar in size and are smaller in primates than in carnivores. They do not show an increase in size in the primate series and, as a result, appear to represent relatively insignificant components of the olivary complex in the larger brains of higher primates. In contrast the medial olivary nucleus increases in size through insectivores, prosimians, monkeys, apes and man. The medial nucleus also shows a specific increase in size in nocturnal as compared to diurnal primates. The functional implications of these variations in development of the primate superior olivary complex are discussed.