The Organization of Human Language Cortex: Special Adaptation or Common Cortical Design?

Abstract

Understanding the neural basis of language is one of the oldest and most difficult pursuits in neuroscience. Despite decades of accumulated data on aphasic subjects with cortical damage, we still know relatively little of how language functions are represented within the neural circuitry of the brain. A major issue of debate is whether language is a species-specific adaptation built into the neocortex, or a by-product of neocortical expansion. Cognitive studies emphasizing the universal nature of language abilities, the consistencies of language structure, and the consistent time course of language development have all indicated that language abilities are innate and must be built into the brain by evolutionary forces. Comparative studies of primates are equivocal since we have little evidence indicating that primate communication is homologous to human language systems. Much of this confusion is related to a lack of information regarding the neural basis of human communication. Recent anatomical data from human brains indicates that left hemisphere regions can have unique types of organization that may be responsible for functional specialization.