Gerald Edelman:

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(Copyright © 2000 Piero Scaruffi | Legal restrictions - Termini d'uso )

Edelman's biological theory of consciousness begins with his theory of how higher-level cognitive functions emerge: from reentrant processes. Consciousness arises from the interaction of two parts of the neural system that differ in their anatomical structure and evolutionary history: the one responsible for categorizing (external stimuli) and the one responsible for "instinctive" behavior (homeostatic control of behavior). At this level concepts are not absolute, but can be remembered.
"Primary consciousness" (being aware of things in the world) therefore arises from "reentrant loops" that interconnect "perceptual categorization" and "value-laden" memory. Primary consciousness has an evolutionary reason to be, since it helps abstract and organize complex changes in the environment.
In order to have higher consciousness the brain must also be able to make the distinction between the self and the rest of the world and to order events in time. A higher-level consciousness (being aware of itself), unique to humans, is then possible if the brain is capable of: perceptual categorization, memory, learning and self-nonself discrimination.
Edelman thinks that two parts of the nervous system differ radically in their evolution, organization and function. And that consciousness emerges as the product of an ongoing categorical comparison of the workings of those two kinds of nervous system. The part that is crucial to consciousness has evolved to be dedicated to adaptive, homeostatic and endocrine functions related to the individual's immediate needs for survival. Such functions therefore reflect evolutionarily selected values that have contributed to fitness. Regions that are assigned to define self within a species include the amygdala, the hippocampus, the limbic system, the hypothalamus. Regions that operate to define nonself include the cortex, the thalamus and the cerebellum.
From an evolutionary point of view, the milestone moment was when a category-value link emerged, because then the basis for consciousness was laid.
Edelman then provides a detailed neurophysiological model of how memory works, in particular how time and space (and successions within them) are represented can be represented by brain organs.
Edelman thinks that concept formation preceded language. Concepts are driven by the perceptual system and stored in memory. With the advent of language concepts become absolute, independent of time. The brain structures that are responsible for concept formation are those that can categorize, discriminate and recombine patterns of activity in different kinds of global mappings. Language was enabled by the evolutionary emergence of special anatomy: the acquisition of phonological capacities provided the means forst for semantics and then for syntax to arise by linking the preexisting conceptual learning with the emerging lexical learning.
The biggest problem of this book (or any other Edelman book) is that its language is very unscientific. There is virtually no single sentence that would survive the scrutiny of a mathematician. Most of them are obscure, especially when it comes to the key concepts. Therefore one is left with the impression that most of it is pure speculation dressed up in obscure sentences in order to appear more scientific than it is. Here is the mother of all examples. To summarize the process that yields consciousness (presumably the most important claim of the book) Edelman writes: "Put otherwise, consciousness is an outcome of a recursively comparative memory in which previous self-nonself categorizations are continually related to ongoing present perceptual categorizations and their short-term succession, before such categorizations have become part of that memory". For all practical purposes this definition is fully equivalent to "blah blah blah blah".

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