Book review of Antonio Damasio

Antonio Damasio:
DESCARTES' ERROR (G.P. Putnam's Sons, 1995)

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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.
Briefly stated, the only thing that matters is what goes on in the brain. The brain maintains a representation of what is going on in the body. A change in the environment may result in a change in the body. This is immediately reflected in the brain's representation of the body state. The brain also creates associations between body states and emotions. Finally, the brain makes decisions by using these associations, whether in conjunction or not with reasoning.
The brain evolved over millions of years for a purpose: it was advantageous to have an organ that could monitor, integrate and regulate all the other organs of the organism. The brain's original purpose was, therefore, to manage the wealth of signals that represent the state of the body ("soma"), signals that come mainly from the inner organs and from muscles and skin. That function is still there, although the brain has evolved many other functions (in particular, for reasoning). Damasio has identified a region of the brain (in the right, "non-dominant" hemisphere) that could be the place where the representation of the body state is maintained. At least, Damasio's experiments show that, when the region is severely damaged (usually after a stroke), the person loses awareness of the left side of the body.
The brain links the body changes with the emotion that accompanies it. For example, the image of a tiger with the emotion of fear. By using both inputs, the brain constructs new representations that encode perceptual information and the body state that occurred soon afterwards. Eventually, the image of a tiger and the emotion of fear, as they keep occurring together, get linked in one brain event. The brain stores the association between the body state and the emotional reaction. That association is a "somatic marker".
Somatic markers are the repertory of emotional learning that we have acquired throughout our lives and that we use for our daily decisions. The somatic marker records emotional reactions to situations. Former emotional reactions to similar past situations is just what the brain uses to reduce the number of possible choices and rapidly select one course of action. There is an internal preference system in the brain that is inherently biased to seek pleasure and avoid pain. When a similar situation occurs again, an "automatic reaction" is triggered by the associated emotion: if the emotion is positive, like pleasure, then the reaction is to favor the situation; if the emotion is negative, like pain or fear, then the reaction is to avoid the situation. The somatic marker works as an alarm bell, either steering us away from choices that experience warns us against or steering us towards choices that experience makes us long for. When the decision is made, we do not necessarily recall the specific experiences that contributed to form the positive or negative feeling.
In philosophical terms, a somatic marker plays the role of both belief and desire. In biological terms, somatic markers help rank "qualitatively" a perception.
In other words, the brain is subject to a sort of "emotional conditioning". Once the brain has "learned" what the emotion associated to a situation, the emotion will influence any decision related to that situation. The brain areas that monitor body changes begin to respond automatically whenever a similar situation arises.
It is a popular belief that emotion must be constrained because it is irrational: too much emotion leads to "irrational" behavior. Instead, Damasio shows that a number of brain-damage cases in which a reduction in emotionality was the cause for "irrational" behaviour.
Somatic markers help make "rational" decisions, and help making them quickly. Emotion, far from being a biological oddity, is actually an integral part of cognition. Reasoning and emotions are not separate: in fact, they cooperate.
Damasio believes that the brain structures responsible for emotion and the ones responsible for reason partially overlap, and this fact lends physical, neural evidence to his hypothesis that emotion and reason cooperate. Those brain structures also communicate directly with the rest of the body, and this suggests the importance of their operations for the organism's survival.

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