Wider Than the Sky: The Phenomenal Gift of Consciousness
http://www.100md.com
《新英格兰医药杂志》
"Consciousness is the guarantor of all we hold to be human and precious. Its permanent loss is considered equivalent to death, even if the body persists in its vital signs." It is with this allusion to the permanent vegetative state that Gerald Edelman opens his latest book, Wider Than the Sky. Edelman aims to answer the question of how the firing of our neurons gives rise to conscious, subjective experiences — or, as philosophers call it, "qualia." He hopes "to disenthrall those who believe the subject is exclusively metaphysical or necessarily mysterious." The title of the book comes from a poem by Emily Dickinson: "The Brain — is wider than the Sky — / For — put them side by side — / The one the other will contain" (circa 1862).
Having laid the groundwork in his critically acclaimed books Neural Darwinism (1987), Topobiology (1988), Remembered Present (1990), Bright Air, Brilliant Fire (1992), and A Universe of Consciousness (2000, written with Giulio Tononi), Edelman here elegantly summarizes his thinking on consciousness. This is, as he calls it himself, a small book, but reading it requires a concentrated effort. Edelman sees his work as a completion of Charles Darwin's in the sense that he views consciousness as a product of evolution, and he cites the idea from Darwin's notebook (1838) that "he who understands baboon will do more toward metaphysics than Locke." Edelman emphasizes that a brain-based explanation of consciousness cannot and need not offer an "explanation that replicates or creates any particular conscious experience," in the same way that a theory that explains how a hurricane arises cannot create the experience of a hurricane or even get one wet "by description."
For Edelman, a biologic theory of consciousness must rest on a global theory of the brain (a reference to Bernard Baars's Global Workspace Theory) and must strictly obey the principles of physics: "no spooky forces that contravene thermodynamics." He makes the distinction between primary and higher-order consciousness. Primary consciousness relates to being mentally aware of a scene, in what Edelman has coined the "remembered present" (a reference to William James's "specious present"). This could be compared to the form of consciousness associated with rapid-eye-movement sleep. Primary consciousness would have evolved as our species did (it remains unclear when), because it increased the chances of survival. According to Edelman, animals with primary consciousness experience qualia but are not conscious of being conscious. Only humans and, "to some minimal degree," higher primates would have a higher-order consciousness that permits them to have a social concept of the self and concepts of the past and the future. Higher consciousness in its most developed form, Edelman thinks, requires the acquisition of language.
Edelman, who won the Nobel Prize in Physiology or Medicine in 1972 for his studies on the structure and diversity of antibodies (which established that the immune system works according to Darwinian principles), once again applies the theory of natural selection to his own theory of neuronal group selection, which he first proposed in 1978. Key to this hypothesis is the proposal that "reentry" is a central organizing principle that governs the functioning of our brains: the dynamic recursive signaling ("reentry") within the thalamocortical system (the "dynamic core") would give rise to our conscious perceptions. These core states change within hundreds of milliseconds as different circuits are activated by stimuli within our environment, our bodies, and our brains. Only some of these states are stable and thus become integrated, giving rise to the unitary property of consciousness. Similarly, memory is considered nonrepresentational and necessarily associative as a result of the interactions among massively degenerate networks. Edelman thinks that computer or machine models of consciousness will not work and that much of cognitive psychology is ill founded, since there are no functional states that can be uniquely equated with defined or coded computational states in individual brains and no processes that can be equated with the execution of algorithms.
"A genuine glimpse into what consciousness is would be the scientific achievement, before which all past achievements would pale. But at present, psychology is in the condition of physics before Galileo," wrote William James in 1899. Edelman's hypotheses, even if they are still far from solving all of the detailed mechanistic problems related to the local operations of networks in the brain, give us such a glimpse. Together with the writings of other pioneers such as Francis Crick, this book has the great merit of offering testable hypotheses to the ever-increasing number of "consciousnologists."
Steven Laureys, M.D., Ph.D.
Université de Liege
4000 Liege, Belgium
steven.laureys@ulg.ac.be(Gerald M. Edelman. 201 pp)
Having laid the groundwork in his critically acclaimed books Neural Darwinism (1987), Topobiology (1988), Remembered Present (1990), Bright Air, Brilliant Fire (1992), and A Universe of Consciousness (2000, written with Giulio Tononi), Edelman here elegantly summarizes his thinking on consciousness. This is, as he calls it himself, a small book, but reading it requires a concentrated effort. Edelman sees his work as a completion of Charles Darwin's in the sense that he views consciousness as a product of evolution, and he cites the idea from Darwin's notebook (1838) that "he who understands baboon will do more toward metaphysics than Locke." Edelman emphasizes that a brain-based explanation of consciousness cannot and need not offer an "explanation that replicates or creates any particular conscious experience," in the same way that a theory that explains how a hurricane arises cannot create the experience of a hurricane or even get one wet "by description."
For Edelman, a biologic theory of consciousness must rest on a global theory of the brain (a reference to Bernard Baars's Global Workspace Theory) and must strictly obey the principles of physics: "no spooky forces that contravene thermodynamics." He makes the distinction between primary and higher-order consciousness. Primary consciousness relates to being mentally aware of a scene, in what Edelman has coined the "remembered present" (a reference to William James's "specious present"). This could be compared to the form of consciousness associated with rapid-eye-movement sleep. Primary consciousness would have evolved as our species did (it remains unclear when), because it increased the chances of survival. According to Edelman, animals with primary consciousness experience qualia but are not conscious of being conscious. Only humans and, "to some minimal degree," higher primates would have a higher-order consciousness that permits them to have a social concept of the self and concepts of the past and the future. Higher consciousness in its most developed form, Edelman thinks, requires the acquisition of language.
Edelman, who won the Nobel Prize in Physiology or Medicine in 1972 for his studies on the structure and diversity of antibodies (which established that the immune system works according to Darwinian principles), once again applies the theory of natural selection to his own theory of neuronal group selection, which he first proposed in 1978. Key to this hypothesis is the proposal that "reentry" is a central organizing principle that governs the functioning of our brains: the dynamic recursive signaling ("reentry") within the thalamocortical system (the "dynamic core") would give rise to our conscious perceptions. These core states change within hundreds of milliseconds as different circuits are activated by stimuli within our environment, our bodies, and our brains. Only some of these states are stable and thus become integrated, giving rise to the unitary property of consciousness. Similarly, memory is considered nonrepresentational and necessarily associative as a result of the interactions among massively degenerate networks. Edelman thinks that computer or machine models of consciousness will not work and that much of cognitive psychology is ill founded, since there are no functional states that can be uniquely equated with defined or coded computational states in individual brains and no processes that can be equated with the execution of algorithms.
"A genuine glimpse into what consciousness is would be the scientific achievement, before which all past achievements would pale. But at present, psychology is in the condition of physics before Galileo," wrote William James in 1899. Edelman's hypotheses, even if they are still far from solving all of the detailed mechanistic problems related to the local operations of networks in the brain, give us such a glimpse. Together with the writings of other pioneers such as Francis Crick, this book has the great merit of offering testable hypotheses to the ever-increasing number of "consciousnologists."
Steven Laureys, M.D., Ph.D.
Université de Liege
4000 Liege, Belgium
steven.laureys@ulg.ac.be(Gerald M. Edelman. 201 pp)