From Pattern Recognition to Sound Localization: a By-product of Growing Larger During Evolution

摘要

Two principal functions of the auditory system are pattern recognition and sound localization. The medial superior olive is traditionally thought to function exclusively in sound localization. In larger mammals, neurons in this nucleus are sensitive to interaural time disparities, a chief cue for sound localization. Mammals with smaller heads do not experience substantial interaural time differences, although most of them also possess a well-developed medial superior olive. This begs the question of what the function of this nucleus in small mammals is, and - since ancestral Mesozoic mammals were small-of its evolutionary origin. We present evidence that the medial superior olive of small mammals serves in the context of pattern recognition, not sound localization. Our results indicate that the evolutionary origin of coding for sound localization in the medial superior olive was serendipitous and occurred only in relatively large mammalian species.