Cortical plasticity within and across lifetimes. Leah Krubitzer

The neocortex is the part of the brain that is involved in perception, cognition, and volitional motor control. In mammals it is a highly dynamic structure that has been dramatically altered within an individual’s lifetime and in different lineages throughout the course of evolution.  These alterations account for the remarkable variations in behavior that species exhibit. Because we cannot study the evolution of the neocortex directly, we must make inferences from comparative analysis of brains as well as developmental mechanisms that give rise to aspects of the phenotype.  Comparative studies allow us to appreciate the types of changes that have been made to the neocortex and the similarities that exist across taxa, and ultimately the constraints imposed on the evolving brain. Developmental studies inform us on how phenotypic transitions may arise by alterations in developmental cascades or changes in the physical environment in which the brain develops. Both genes and the sensory environment contribute to aspects of the phenotype and similar features, such as the size of a cortical field, can be altered in a variety of ways.  Although both genes and the laws of physics place formidable constraints on the evolution of the neocortex, mammals have evolved a number of mechanisms that allow them to loosen these constraints and often alter the course of their own evolution.