The brain exhibits all of the properties of an evolutionary system. In the developing brain, there is an initial oversupply of neurons. The combinatorial possibilities that exist within and between neuronal groups is a source of variation that is selected from. The brain, which is only approx. 25% formed at birth, matures through processes of degeneracy and associativity. The dynamic interplay between the variation and selection of neuronal groups is a source of self-organisation. The brain has the capacity to store patterns of activation and to recreate acts separated in time from the original events. Memory biases the processes of organisation towards increased complexity. (For a more extensive explanation of the brain as an evolutionary system see Edelman 1987; 1993; 2004).
To be honest, I have not met many people who truly understand every aspect of Edelman’s theory of neuronal group selection (TNGS). In fact, if I have gone some way to understanding some part of his theory, then it has been largely through my reading of secondary literature material, returning frequently to his new books and then discussing his work with some of my friends like Dr Juan Dominguez and Dr Ryszard Maleszka who give me the impression they suitably understand TNGS. I look forward to hopefully discussing TNGS with Daniel Lende one day who wrote a fantastic blog about Changeux and Edelman
My favourite work of Edelman’s is his book called “A Universe of Consciousness“, but the most accessible books for most readers are: Wider than the sky and Bright Air, Brilliant Fire.
My favourite Edelman quote (and possibly Edelman’s favourite as well):
“If our view of memory is correct, in higher organisms every act of perception is, to some degree, an act of creation, and every act of memory is, to some degree, an act of imagination.”
(Edelman and Tononi, 2000:101)
Edelman’s Theory of Neuronal Group Selection (TNGS) takes an integrative approach that situates brain science in relation to physics and evolutionary biology. A central part of TNGS is the proposal that the brain operates as a selectional system—using homeostatic guides and value-category memory systems, it selects from a diversity of behaviours and internal states which are represented in functional neuronal groups. Consciousness, in Edelman’s view, is due to the distributed activities of populations of neurons in many different areas of the brain.
Small aside: Whilst Edelman himself doesn’t subscribe to any branch of mysticism, the idea that what we see is an internal construct and what we remember is an imagination is congruent to Hinduism’s notion of maya (the world is an illusion). Similarly, Edelman’s proposal that there is no homunculus closely parallels the Buddhist notion that there is no essential self. Indeed, the idea that what we see is an internal construct and what we remember is an imagination fits nicely not only with leading philosophers of mind (e.g. Gerald Edelman & Daniel Dennet), but with the ancient wisdom of Buddhist sages.
Edelman relates physiological mechanisms to psychological behaviours through a process called perceptual categorisation. The function of perceptual categorization in the vertebrate nervous system is to maintain homeostasis between the internal and external environment. Perceptual categorization is the ability to selectively discriminate objects or events within an unlabelled environment. Edelman assumes that the resulting categories are useful to a given species and are adaptive. Perceptual categorization and concept formation (maps of perceptual maps) would not be adaptive to an animal in the absence of memory, an essential component of consciousness. Primary consciousness is the result of the dynamic interaction between ongoing perception and memory through the reentrant connections in the thalamocortical system. This evolutionary development has led to our ability to construct and form a meaningful picture of the world. Perceptual categorization is a process that both depends upon and leads to action within that scene. Edelman’s theory, of how this neural activity in the reentrant dynamic core phenomenally transforms into higher order consciousness, verges on the epiphenomenal. Though, he suggests that his theory eliminates this paradox when properly understood. Whilst Wider than the sky is his most accessible book, it still can lose the reader in jargon, as do his earlier works.
So let me go over some things again and revise Edelman’s position:
Edelman believes that consciousness is a unitary phenomenon that arises from the contemporaneous activities of distributed populations of neurons. He suggests that any biological theory of mind demands that psychological behaviours are firmly embedded in neurophysiological mechanisms (this is perhaps where Dr Daniel Lende would correctly suggest Edelman needs some sound anthropology as well). Perceptual categorization is a function of the brain that relates psychological activity to underlying physiological processes. It represents the ability of the vertebrate nervous system to maintain homeostasis between internally determined reference levels and external disturbances. Perceptual categorization is the ability to selectively discriminate objects or events within an unlabelled environment. When coupled with memory, perceptual categorization and concept formation (maps of perceptual maps) become adaptive to an animal. Primary consciousness is the result of the dynamic interaction between ongoing perception and memory through the reentrant connections in the thalamocortical system.
Overall, Edelman’s polemic is intuitively appealing, but relevant data can be scarce. Parts of his theory, however, have been contested. In looking for a biological theory of consciousness, we can quickly dismiss non-biological theories. The one neuron:one quale computational approach of neuroscience researchers such as Francis Crick and Semir Zeki have serious difficulties in terms of testability (what is it sometimes referred to? The Grandmother cell theory?). William Calvin would certainly differ with Edelman’s concept of value-category memory, suggesting that humans don’t always select beneficial alternatives. Indeed, if humans do have internal value systems for navigating the external environment, then if I may make assumptions about Calvin’s perspective, then perhaps it would be a matter of retraining these values in order to properly balance our long-term needs with our short-term desires.
Edelman, G.E. (1987) Neural Darwinism: The Theory of Neuronal Group Selection. New York: Basic Books, 1987.
Edelman, G.E. (2004) Wider than the sky: the phenomenal gift of consciousness. Yale University Press.
Edelman, G.E. (1993) Bright Air, Brilliant Fire: On the Matter of Mind. New York: Basic Books.
Edelman, G.E. & Gally, J.A. (2001) Degeneracy and complexity in biological systems. Proceedings of the National Academy of Sciences. 98(24), 13763-13768.
Tononi, G., Sporns, O., Edelman, G.E. (1999) Measures of degeneracy and redundancy in biological networks. Proceedings of the National Academy of Science USA, 96(6), 3257-62.