Why Can Birds Be So Smart? Background, Significance, and Implications of the Revised View of the Avian Brain

In the early twentieth century, the anatomical nomenclature of the avian telencephalon (cerebrum) was developed on the basis of flawed assumptions about homology to mammals. The classic terminology implied that the majority of the avian telencephalon was basically composed of nuclei forming massive basal ganglia which controlled only simple, unlearned behavior. Later research revealed that this assumption was inaccurate and that the avian telencephalon contains a welldeveloped pallium in addition to basal ganglia. The avian pallium is equivalent to specific mammalian counterparts (e.g., neocortex, claustrum, and/or amygdala) that are responsible for complex and sophisticated behavior. In 2002, based on a revised interpretation of the avian brain organization, the new nomenclature was proposed by comparative neuroscientists who participated in the Avian Brain Nomenclature Forum. This paper presents the general background and significance of the revised view of the avian brain, as well as implications for understanding the remarkable cognitive abilities of birds.