reviewed by Piero Scaruffi
(Root page for Piero's web site)
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 per-
cepts 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 interac-
tion: between the body and the brain, and between them and the
environment.
Damasio formulates the somatic-marker hypothesis: a special class of
feelings, acquired by experience, express predicted future outcomes of
known situations and help the mind make decisions.
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. Nonethe-
less, 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, emo-
tions, 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 infor-
mation is processed, moving from station to station through the brain,
each station creates new connections reaching back to the earlier lev-
els 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 prefron-
tal 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 informa-
tion. 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.
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