Scientific Understanding of Consciousness
Consciousness as an Emergent Property of Thalamocortical Activity

Convergence Zones for Language

 

Dr. Antonio Damasio, a neurologist with his wife Dr. Hannah Damasio, has developed a theory of cognition and language that is receiving rave reviews from linguists and neuroscientists.

The brain has special areas for processing language very much along the lines of Dr. Ojemann's essential areas, Dr. Damasio said, but these areas do not constitute an independent language organ with little boxes where nouns, verbs and other language features are processed.

Rather, the essential areas can be thought of as "convergence zones" where the key to the combination of components of words and objects is stored. Thus knowledge of words and concepts is distributed widely throughout the brain but needs a third-party mediator -- the convergence zone -- to bring the knowledge together, during reactivation.

An example helps explain this difficult concept, Dr. Damasio said. "When I ask you to think about a styrofoam cup," he said, "you do not go into a filing cabinet in your brain and come up with a ready-made picture of a cup. Instead, you compose an internal image of a cup drawn from its features. The cup is part of a cone, white, crushable, three inches high and can be manipulated.

"In reactivating the concept of this cup," Dr. Damasio said, "you draw on distant clusters of neurons that separately store knowledge of cones, the color white, crushable objects and manipulated objects. Those clusters are activated simultaneously by feedback firing from a convergence zone. You can attend to the revival of those components in your mind's eye and from an internal image of the whole object."

The same process is true of words, Dr. Damasio said. "When I ask you to tell me what the object is, you do not go into a filing cabinet where the word 'cup' is stored," he said. "Rather, you use a convergence zone for the word 'cup' by activating distant clusters of neurons that store the phonemes 'c' and 'u' and 'p'. You can perceive their momentary revival in your mind's ear or allow them to activate the motor system and vocalize the word 'cup.' "

To read, speak or make other lexical operations about a styrofoam cup, the brain requires a third-party convergence zone that mediates between word and concept convergence zones, the scientist said. "Only then can we operate linguistically and evoke the word from the concept or vice versa," Dr. Damasio said.

Convergence zones are probably established in early childhood during language learning and as memories are formed, Dr. Damasio said. New ones are formed and old ones can be rearranged throughout life.

 

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