Some principles of brain evolution

Abstract

The evolutionary changes in all parts of the brain occur in gray and white matter. Many changes in the brain stem have resulted in a diverse set of locomotor patterns. The red nucleus in terrestrial vertebrates was differentiated from the tegmentum of fish and amphibians. The red nucleus structure has changed considerably during verte­brate and mammalian development. In lower vertebrates the larger neurons are the predominate form and dur­ing the evolution the number of these neurons diminishes and the number of the small neurons increases con­stantly. The rubrospinal tract progressively declines from lower mammals to primates. This could be linked to the loss of locomotor activity of the upper extremities. The differentiation of respective cortical areas is an important process in the evolution of the cerebral cortex. The common sensorimotor cortex in lower mammals is differentiated into sensory and motor areas. Human speech led to the formation of Broca`s speech area and Wernicke`s area probably half a million years ago. The birth of lit­eracy, about 5000 years ago caused the formation of the Exner`s Writing Area, which is still connected to many other areas of the cerebral cortex and other brain structures.