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Gerald Maurice Edelman (born July 1, 1929) is an American biologist who shared the 1972 Nobel Prize in Physiology or Medicine for work with Rodney Robert Porter on the immune system.[1] Edelman's Nobel Prize-winning research concerned discovery of the structure of antibody molecules.[2] In interviews, he has said that the way the components of the immune system evolve over the life of the individual is analogous to the way the components of the brain evolve in a lifetime. There is a continuity in this way between his work on the immune system, for which he won the Nobel Prize, and his later work in neuroscience and in philosophy of mind.

Education and careerEdit

Gerald Edelman was born in 1929 in Ozone Park, Queens, New York, to Ashkenazi Jewish parents, physician Edward Edelman, and Anna (née Freedman) Edelman, who worked in the insurance industry.[3] After being raised in New York, he attended college in Pennsylvania where he graduated magna cum laude with a B.S. from Ursinus College in 1950 and received an M.D. from the University of Pennsylvania School of Medicine in 1954.[3]

After a year at the Johnson Foundation for Medical Physics, he became a house officer at the Massachusetts General Hospital and then practiced medicine in France while serving with US Army Medical Corps.[3] Edelman joined the Rockefeller Institute for Medical Research as a graduate fellow in 1957, working in the laboratory of Henry Kunkel and receiving a Ph.D. in 1960.[3] Rockefeller made him the Assistant (later Associate) Dean of Graduate Studies until 1966, when he became a professor at the school.[3] In 1992, he moved to California and became a professor of neurobiology at The Scripps Research Institute.[4]

After his Nobel prize award, Edelman began research into the regulation of primary cellular processes, particularly the control of cell growth and the development in multi-celled organisms, focussing on cell-to-cell interactions in early embryonic development and in the formation and function of the nervous system. These studies led to the discovery of cell adhesion molecules (CAMs), which guide the fundamental processes that help an animal achieve its shape and form, and by which nervous systems are built. One of the most significant discoveries made in this research is that the precursor gene for the neural cell adhesion molecule gave rise in evolution to the entire molecular system of adaptive immunity.[5]

Edelman is the founder and director of The Neurosciences Institute, a nonprofit research center in San Diego that studies the biological bases of higher brain function in humans, and is on the scientific board of the World Knowledge Dialogue project.[6]

Edelman is a member of the USA Science and Engineering Festival's Advisory Board.[7]

Nobel PrizeEdit

While in Paris serving in the Army, Edelman read a book that sparked his interest in antibodies.[8] He decided that, since the book said so little about antibodies, he would investigate them further upon returning to the United States, which led him to study physical chemistry for his 1960 Ph.D.[8] Research by Edelman and his colleagues and Rodney Robert Porter in the early 1960s produced fundamental breakthroughs in the understanding of the antibody's chemical structure, opening a door for further study.[9] For this work, Edelman and Porter shared the Nobel Prize in Physiology or Medicine in 1972.[1]

In its Nobel Prize press release in 1972, the Karolinska Institutet lauded Edelman and Porter's work as a major breakthrough:

"The impact of Edelman's and Porter's discoveries is explained by the fact that they provided a clear picture of the structure and mode of action of a group of biologically particularly important substances. By this they laid a firm foundation for truly rational research, something that was previously largely lacking in immunology. Their discoveries represent clearly a break-through that immediately incited a fervent research activity the whole world over, in all fields of immunological science, yielding results of practical value for clinical diagnostics and therapy.[10]

Disulfide bondsEdit

File:Anticorps.png
Diagram illustrating the disulfide bonds (red) that link the light (green) and heavy (blue) protein subunits of Immunoglobulin G (IgM)molecules. This diagram also illustrates the relative positions of the variable (V) and constant (C) domains of an IgG molecule. The heavy and light chain variable regions come together to form antigen binding sites at the end of the two symmetrical arms of the antibody.

Edelman's early research on the structure of antibody proteins revealed that disulfide bonds link together the protein subunits.[2] The protein subunits of antibodies are of two types, the larger heavy chains and the smaller light chains. Two light and two heavy chains are linked together by disulfide bonds to form a functional antibody.

Molecular models of antibody structureEdit

Using experimental data from his own research and the work of others, Edelman developed molecular models of antibody proteins.[11] A key feature of these models included the idea that the antigen binding domains of antibodies (Fab) include amino acids from both the light and heavy protein subunits. The inter-chain disulfide bonds help bring together the two parts of the antigen binding domain.

Antibody sequencingEdit

Edelman and his colleagues used cyanogen bromide and proteases to fragment the antibody protein subunits into smaller pieces that could be analyzed for determination of their amino acid sequence.[12][13] At the time when the first complete antibody sequence was determined (1969)[14] it was the largest complete protein sequence that had ever been determined. The availability of amino acid sequences of antibody proteins allowed recognition of the fact that the body can produce many different antibody protein with similar antibody constant regions and divergent antibody variable regions.

TopobiologyEdit

Topobiology is Edelman’s theory which asserts that morphogenesis is driven by differential adhesive interactions among heterogeneous cell populations and it explains how a single cell can give rise to a complex multi-cellular organism. As proposed by Edelman in 1988 topobiology is the process that sculpts and maintains differentiated tissues and is acquired by the energetically favored segregation of cells through heterologous cellular interactions.

Theory of consciousnessEdit


Edelman is noted for his theory of consciousness, which he has documented in a trilogy of technical books, and in several subsequent books written for a general audience including Bright Air, Brilliant Fire (1992), A Universe of Consciousness (2001, with Giulio Tononi), Wider than the Sky (2004) and Second Nature: Brain Science and Human Knowledge (2007).

In Second Nature Edelman defines human consciousness as being:

"... what you lose on entering a dreamless deep sleep ... deep anesthesia or coma ... what you regain after emerging from these states. [The] experience of a unitary scene composed variably of sensory responses ... memories ... situatedness ... "

The first of Edelman's technical books, Neural Darwinism (1987) explores his theory of memory that is built around the idea of plasticity in the neural network in response to the environment. The second book, Topobiology (1988), proposes a theory of how the original neuronal network of a newborn's brain is established during development of the embryo. The Remembered Present (1990) contains an extended exposition of his theory of consciousness.

Edelman has asked whether we should attempt to construct models of functioning minds or models of brains which, through interactions with their surroundings, can develop minds. His answer is that we should make model brains and pay attention to how they interact with their environment. Edelman accepts the existence of qualia and incorporates them into his brain-based theory of consciousness. His concept of qualia attempts to avoid the pitfalls of the idea of special qualia with non-functional properties, which was criticized by Daniel Dennett.

Edelman proposes a biological theory of consciousness, based on his studies of the immune system. He explicitly locates his theory within Charles Darwin's Theory of Natural Selection, citing the key tenets of Darwin's population theory, which postulates that individual variation within species provides the basis for the natural selection that eventually leads to the evolution of new species.[15] He rejects dualism and also dismisses newer hypotheses such as the so-called 'computational' model of consciousness, which liken the brain's functions to the operations of a computer.

Edelman argues that the mind and consciousness are wholly material and purely biological phenomena, arising from highly complex cellular processes within the brain, and that the development of consciousness and intelligence can be satisfactorily explained by Darwinian theory.

In Edelman's view, human consciousness depends on and arises from the uniquely complex physiology of the human brain:

  • the vast number of neurons and associated cells in the brain
  • the almost infinitely complex physiological variations in neurons (even of the same general type) and in their connections with other cells
  • the massive multiple parallel reentrant connections between individual cells, and between larger neuronal groups, and so on, up to entire functional regions and beyond.

Edelman's theory is strongly anti-reductionist and seeks to explain consciousness by reference to the extraordinarily rich and complex morphology of the brain. A newborn baby's brain comprises a massive population of neurons (approx. 100 billion cells) and those that survive the initial phases of growth and development will make approximately 100 trillion connections with each other. A sample of brain tissue the size of a match head contains about a billion connections, and if we consider how these neuronal connections might be variously combined, the number of possible permutations becomes hyper-astronomical—in the order of ten followed by millions of zeros.[16] The young brain contains many more neurons than will ultimately survive to maturity and Edelman argues that this great redundant capacity is needed because neurons are the only cells in the body that cannot be renewed and because only those cells and networks best adapted to their ultimate purpose will be selected as they organise into neuronal groups.

Neural DarwinismEdit

Edelman's theory of neuronal group selection, also known as Neural Darwinism, has three basic tenets—Developmental Selection, Experiential Selection and Reentry.

  • Developmental selection -- the formation of the gross anatomy of the brain is controlled by genetic factors, but in any individual the connectivity between neurons at the synaptic level and their organisation into functional neuronal groups is determined by somatic selection during growth and development. This process generates tremendous variability in the neural circuitry—like the fingerprint or the iris, no two people will have precisely the same synaptic structures in any comparable area of brain tissue. Their high degree of functional plasticity and the extraordinary density of their interconnections enables neuronal groups to self-organise into many complex and adaptable "modules". These are made up of many different types of neurons which are typically more closely and densely connected to each other than they are to neurons in other groups.
  • Experiential selection -- Overlapping the initial growth and development of the brain, and extending throughout an individual's life, a continuous process of synaptic selection occurs within the diverse repertoires of neuronal groups. This process may strengthen or weaken the connections between groups of neurons and it is constrained by value signals that arise from the activity of the ascending systems of the brain, which are continually modified by successful output. Experiential selection generates dynamic systems that can 'map' complex spatio-temporal events from the sensory organs, body systems and other neuronal groups in the brain onto other selected neuronal groups. Edelman argues that this dynamic selective process is directly analogous to the processes of selection that act on populations of individuals in species, and he also points out that this functional plasticity is imperative, since not even the vast coding capability of entire human genome is sufficient to explicitly specify the astronomically complex synaptic structures of the developing brain.[17]
  • Reentry
Main article: Reentry (neural circuitry)-- the third tenet of Edelman's thesis is the concept of reentrant signalling between neuronal groups. He defines reentry as the ongoing recursive dynamic interchange of signals that occurs in parallel between brain maps, and which continuously interrelates these maps to each other in time and space (film clip: Edelman demonstrates spontaneous group formation among neurons with re-entrant connections [18]). Reentry depends for its operations on the intricate networks of massively parallel reciprocal connections within and between neuronal groups, which arise through the processes of developmental and experiential selection outlined above. Edelman describes reentry as "a form of ongoing higher-order selection ... that appears to be unique to animal brains" and that "there is no other object in the known universe so completely distinguished by reentrant circuitry as the human brain".

Evolution theoryEdit

Edelman and Gally were the first to point out the pervasiveness of Degeneracy in biological systems and the fundamental role that degeneracy plays in facilitating evolution.[19]

PersonalEdit

Edelman married Maxine M. Morrison in 1950.[3] They have two sons, Eric, a visual artist in New York City, and David, a neuroscientist at Bennington College. Their daughter, Judith Edelman, is a bluegrass musician and recording artist.

PublicationsEdit

  • Neural Darwinism: The Theory of Neuronal Group Selection (Basic Books, New York 1987). ISBN 0192860895
  • Topobiology: An Introduction to Molecular Embryology (Basic Books, 1988, Reissue edition 1993) ISBN 0465086535
  • The Remembered Present: A Biological Theory of Consciousness (Basic Books, New York 1990). ISBN 046506910X
  • Bright Air, Brilliant Fire: On the Matter of the Mind (Basic Books, 1992, Reprint edition 1993). ISBN 0465007643
  • The Brain, Edelman and Jean-Pierre Changeux, editors, (Transaction Publishers, 2000). ISBN 0765807173
  • A Universe of Consciousness: How Matter Becomes Imagination, Edelman and Giulio Tononi, coauthors, (Basic Books, 2000, Reprint edition 2001). ISBN 0465013775
  • Wider than the Sky: The Phenomenal Gift of Consciousness (Yale Univ. Press 2004) ISBN 0300102291

See alsoEdit

ReferencesEdit

  1. 1.0 1.1 The Nobel Prize in Physiology or Medicine 1972. URL accessed on 2007-09-27.
  2. 2.0 2.1 Structural differences among antibodies of different specificities by G. M. Edelman, B. Benacerraf, Z. Ovary and M. D. Poulik in Proc Natl Acad Sci U S A (1961) volume 47, pages 1751-1758.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 (1973). Gerald M. Edelman: Biography. Les Prix Nobel en 1972. Nobel Foundation. URL accessed on 2007-09-27. (Including Addendum, May 2005.)
  4. Gerald M. Edelman: Curriculum Vitae. (PDF) URL accessed on 2007-09-27.
  5. Nobelprize.org - Gerald M. Edelman biography
  6. World Knowledge Dialogue. URL accessed on 2007-10-12.
  7. http://www.usasciencefestival.org/about/advisors
  8. 8.0 8.1 Frontiers Profile: Gerry Edelman. URL accessed on 2007-09-27.
  9. Karolinksa Institutet (October 1972). The Nobel Prize in Physiology or Medicine 1972. Press release. Retrieved on 2007-09-27. “Their discoveries represent clearly a break-through that immediately incited a fervent research activity the whole world over [...]”
  10. Kaarolinska Institutet press release, October 1972
  11. PMID 14173001 (PMID 14173001)
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  12. PMID 5650389 (PMID 5650389)
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  13. PMID 4177258 (PMID 4177258)
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  14. PMID 5257969 (PMID 5257969)
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  15. Gerald M. Edelman & Jean-Pierre Changeux (eds), The Brain (Transaction Publishers, 2001), p.45
  16. Gerald Edelman, Bright Air, Brilliant Fire (Penguin, 1992), p.17
  17. Gerald Edelman, Bright Air, Brilliant Fire (Penguin, 1992), p.224
  18. Gerald Edelman: "From Brain Dynamics to Consciousness: A Prelude to the Future of Brain-Based Devices", Video, IBM Lecture on Cognitive Computing, June 2006
  19. Edelman and Gally (2001). Degeneracy and complexity in biological systems. Proceedings of the National Academy of Sciences, USA 98 (24): 13763–13768.

External link Edit

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