(Copyright © 1999 Piero Scaruffi | Legal restrictions - Termini d'uso )
Damasio is trying to build a neurobiology of rationality.
In this book he provides a neurophysiological analysis of memory, emotions and consciousness.
The book has three themes. 1. Human reason depends on the interaction among several brain systems rather than on a single brain centre. 2. Feelings are views of the body's internal organs. Feelings are percepts and they are as cognitive as any other percept. 3. The mind is about the body: the neural processes that are experienced as the mind are about the representation of the body in the brain. The mental requires the existence of a body for more than mere support: the mind is not a phenomenon of the brain alone. The mind derives from the entire organism as a whole. The mind reflects two types of interaction: between the body and the brain, and between them and the environment.
The neural basis for the self resides with the continous reactivation of 1. the individual's past experience (which provides the individual's sense of identity) and 2. a representation of the individual's body (which provides the individual's sense of a whole). The self is continously reconstructed. This is a purely non-verbal process: language is not a prerequisite for consciousness. Nonetheless, language is the source of the "I", a second order narrative capacity. Damasio's "embodied mind" is closely related to Edelman's "self imbued with value".
Damasio's theory of convergence zones (not presented in this book) is tackling the issue of consciousness. When an image enters the brain via the visual cortex, it is channelled through "convergence zones" in the brain until it is identified. Each convergence zone handles a category of objects (faces, animals, trees, etc): a convergence zone does not store permanent memories of words and concepts but helps reconstructing them. Once the image has been identified, an acoustical pattern corresponding to the image is constructed by another area of the brain. Finally an articulatory pattern is constructed so that the word that the image represents can be spoken. There are about twenty known categories that the brain uses to organize knowledge: fruits/vegetables, plants, animals, body parts, colors, numbers, letters, nouns, verbs, proper names, faces, facial expressions, emotions, sounds.
"Convergence zones" are indexes that draw information from other areas of the brain. The memory of something is stored in bits at the back of the brain (near the gateways of the senses): features are recognized and combined and an index of these features is formed and stored. When the brain needs to bring back the memory of something, it will follow the instructions in that index, recover all the features and link them to other associated categories. As information is processed, moving from station to station through the brain, each station creates new connections reaching back to the earlier levels of processing. These connections always allows the brain to work in reverse. Convergence zones may be common to all individuals or different from individual to individual, based on experience.
Emotions are the brain's interpretation of reactions to changes in the world. Emotional memories involving fear can never be erased The prefrontal cortex, amygdala and right cerebral cortex form a system for reasoning that gives rise to emotions and feelings. The prefrontal cortex and the amygdala process a visual stimulus by comparing it with previous experience and generate a response that is transmitted both to the body and to the back of the brain.
Convergence zones are organized in a hierarchy: lower convergence zones pass information to higher convergence zones. Lower zones select relevant details from sensorial information and send summaries to higher zones, which successively refine and integrate the information. In order to be conscious of something a higher convergence zone must retrieve from the lower convergence zones all the sensory fragments that are related to that something. Therefore, consciousness occurs when the higher convergence zones fire signals back to lower convergence zones.
In this book
Damasio formulated the "somatic-marker hypothesis", but it was barely
sketched. It will be refined as follows in following writings.