The proto-cortical amygdala: a perspective on the functional and evolutionary relationship between the basolateral amygdala complex and neocortex in mammals

The basolateral amygdala complex (BNC) plays an important role in learning, memory, motivation, and social behaviour, with its dysfunction implicated in a wide variety of psychiatric disorders. Despite being one of the most intensely researched areas of the brain, much is still unknown about its microanatomical structure and function, relationships and evolutionary origins. In this review, we offer a multidisciplinary approach through the lens of comparative anatomy and evolutionary developmental studies to provide a better understanding of the anatomical and functional relationship between the amygdala and cortex in memory, learning, and social behaviour. Particular attention is paid to the evolutionary origin of pallial areas across amniotes, as well as homology between principal neurons, cortical layers, BNC nuclei, and connectivity between these areas. We argue that the basolateral amygdala complex functions as an early form of the mammalian neocortex. This theory will help to further the understanding of amygdala and cortex function in both health and psychiatric disease.