From Scientific American
When he was still a student, Richard Feynman hinted at a career to come as a scientific wonderer when he wrote: "I wonder why. I wonder why. / I wonder why I wonder / I wonder why I wonder why / I wonder why I wonder!" Such wondering, and meta-wondering, takes us to the heart of what geneticist-cum-neuroscientist Francis Crick (who would know) calls "the major unsolved problem in biology"--explaining how billions of neurons swapping chemicals give rise to such subjective experiences as consciousness, self-awareness, and awareness that others are conscious and self-aware. The body of literature attempting to solve this problem is extensive, and getting one's mind around the field is a herculean task successfully executed by psychologist Susan Blackmore in her delightful introduction, Consciousness. Presented as a textbook, it is so highly engaging that I recommend it for general readers, too. In many ways, the book is structured like a brain, with loads of independent modules (boxes and sidebars featuring profiles, concepts and activities) tied together by a flowing narrative and integrated into a conceptual whole. The easy problem, Blackmore says, is explaining each of the functional parts of the brain, such as "the discrimination of stimuli, focusing of attention, accessing and reporting mental states, deliberate control of behavior, or differences between waking and sleep." In contrast, the hard problem in consciousness studies "is experience: what it is like to be an organism, or to be in a given mental state." Adding up all of the solved easy problems does not equal a solution to the hard problem. Something else is going on in private subjective experiences--called qualia--and there is no consensus on what it is. Dualists hold that qualia are separate from physical objects in the world and that mind is more than brain. Materialists contend that qualia are ultimately explicable through the activities of neurons and that mind and brain are one. Blackmore, uniquely qualified to assess all comers (she sports multihued hair, is a devotee of meditation, and studies altered states of consciousness), allows the myriad theorists to make their case (including her own meme-centered theory) so that you can be the judge. Making a strong case for the materialist position is Gerald M. Edelman's latest contribution, Wider Than the Sky, offered as a "concise and understandable" explanation of consciousness "to the general reader." Concise it is, but as for understandable, Edelman understates: "It will certainly require a concentrated effort on the part of the reader." As director of the Neurosciences Institute in La Jolla, Calif., a Nobel laureate and author of several books on consciousness (Neural Darwinism, The Remembered Present and Bright Air, Brilliant Fire), Edelman has impeccable credentials. But science writing for a general audience involves more than expunging scholarly references and providing a glossary of technical terms as a substitute for clear exposition. To wit, on memory Edelman writes that "it is more fruitfully looked on as a property of degenerate nonlinear interactions in a multidimensional network of neuronal groups." Such prose is common throughout the book, which is a shame because Edelman is a luminously entertaining conversationalist, and his theory that the brain develops in a Darwinian fashion of neuronal variation and selection, and that consciousness is an emergent property of increasingly complex and integrated neuronal groups, has considerable support from neuroscience research. An ideal combination of exquisite prose and rigorous science can be found in California Institute of Technology neuroscientist Christof Koch's The Quest for Consciousness. A rock climber adorned with a tattoo of the Apple Computer logo on his arm, Koch takes an unabashed neurobiological approach, the natural extension of what his longtime collaborator Francis Crick started in 1994 when he wrote in The Astonishing Hypothesis "that 'you,' your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules." To me, the most astonishing aspect of this theory is that it is astonishing to anyone. Where else could the mind be but in the brain? Nevertheless, finding the neuronal correlates of consciousness (NCC) has proved elusive, so instead of concocting a grand unified theory, Koch and Crick undertook a very specific research program focusing on the visual system, to understand precisely how photons of light striking your retina become fully integrated visual experiences. Koch and his colleagues, for example, discovered a single neuron that fires only when the subject sees an image of President Bill Clinton. If this neuron died, would Clinton be impeached from the brain? No, because the visual representation of Clinton is distributed throughout several areas of the brain, in a hierarchical fashion, eventually branching down to this single neuron. The visual coding of any face involves several groups of neurons--one to identify the face, another to read its expression, a third to track its motion, and so on. This hierarchy of data processing allows the brain to economize neural activity through the use of combinatorics: "Assume that two face neurons responded either not at all or by firing vigorously. Between them, they could represent four faces (one face is encoded by both cells not firing, the second one by firing activity in one and silence in the other, and so on). Ten neurons could encode 210, or about a thousand faces.... It has been calculated that less than one hundred neurons are sufficient to distinguish one out of thousands of faces in a robust manner. Considering that there are around 100,000 cells below a square millimeter of cortex, the potential representational capacity of any one cortical region is enormous." Given that the brain has about 100 billion neurons, consciousness is most likely an emergent property of these hierarchical and combinatoric neuronal connections. How, precisely, the NCC produce qualia remains to be explained, but Koch's scientific approach, in my opinion, is the only one that will solve the hard problem.
Michael Shermer writes the Skeptic column for Scientific American and is publisher of Skeptic and author of The Science of Good and Evil (Henry Holt and Company, 2004).
From The New England Journal of Medicine
"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.
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