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<ul><li><p>112</p><p>How the BrainCreates the Mind</p><p>Philosophers, neuroscientists and laypeople have long wondered </p><p>how the conscious mind comes to be. A more complete understanding </p><p>of the workings of the brain ought to lead to an eventual solution</p><p>As the millennium draws to a close, it is apparent that one question towers above all others in</p><p>the life sciences: How does the set of processes we call mind emerge from the activity of</p><p>the organ we call brain? The question is hardly new. It has been formulated in one way</p><p>or another for centuries. Once it became possible to pose the question and not be</p><p>burned at the stake, it has been asked openly and insistently. Recently the question has preoccupied both</p><p>the expertsneuroscientists, cognitive scientists and philosophersand others who wonder about the ori-</p><p>gin of the mind, specifically the conscious mind.</p><p>The question of consciousness now occupies center stage because biology in general and neuroscience in</p><p>particular have been so remarkably successful at unraveling a great many of lifes secrets. More may have</p><p>been learned about the brain and the mind in the 1990sthe so-called decade of the brainthan during the</p><p>entire previous history of psychology and neuroscience. Elucidating the neurobiological basis of the con-</p><p>scious minda version of the classic mind-body problemhas become almost a residual challenge.</p><p>Contemplation of the mind may induce timidity in the contemplator, especially when consciousness be-</p><p>comes the focus of the inquiry. Some thinkers, expert and amateur alike, believe the question may be unanswer-</p><p>able in principle. For others, the relentless and exponential increase in new knowledge may give rise to a vertigi-</p><p>nous feeling that no problem can resist the assault of science if only the theory is right and the techniques are</p><p>powerful enough. The debate is intriguing and even unexpected, as no com-</p><p>parable doubts have been raised over the likelihood of explaining how the</p><p>brain is responsible for processes such as vision or memory, which are obvious</p><p>components of the larger process of the conscious mind.</p><p>The multimedia mind-show occurs constantly as the brainprocesses external and internalsensory events. As the brain answers the unasked question of who is experiencing the mind-show, the sense of self emerges.</p><p>by Antonio R. Damasio</p><p>SLIM</p><p> FIL</p><p>MS</p><p>Copyright 1999 Scientific American, Inc.</p></li><li><p>Copyright 1999 Scientific American, Inc.</p></li><li><p>I am firmly in the confident camp: a substantialexplanation for the minds emergence from thebrain will be produced and perhaps soon. Thegiddy feeling, however, is tempered by the ac-knowledgment of some sobering difficulties.</p><p>Nothing is more familiar than the mind. Yetthe pilgrim in search of the sources and mecha-nisms behind the mind embarks on a journeyinto a strange and exotic landscape. In no particu-lar order, what follows are the main problems fac-ing those who seek the biological basis for theconscious mind.</p><p>The first quandary involves the perspectiveone must adopt to study the conscious mind inrelation to the brain in which we believe it origi-nates. Anyones body and brain are observable tothird parties; the mind, though, is observableonly to its owner. Multiple individuals confront-ed with the same body or brain can make thesame observations of that body or brain, but nocomparable direct third-person observation ispossible for anyones mind. The body and itsbrain are public, exposed, external and unequiv-ocally objective entities. The mind is a private,hidden, internal, unequivocally subjective entity.</p><p>How and where then does the dependence of afirst-person mind on a third-person body occurprecisely? Techniques used to study the brain in-clude refined brain scans and the measurement ofpatterns of activity in the brains neurons. Thenaysayers argue that the exhaustive compilation</p><p>of all these data adds up to correlates of mentalstates but nothing resembling an actual mentalstate. For them, detailed observation of livingmatter thus leads not to mind but simply to thedetails of living matter. The understanding ofhow living matter generates the sense of self thatis the hallmark of a conscious mindthe sensethat the images in my mind are mine and areformed in my perspectiveis simply not possible.This argument, though incorrect, tends to silencemost hopeful investigators of the conscious mind.</p><p>To the pessimists, the conscious-mind problemseems so intractable that it is not even possible toexplain why the mind is even about somethingwhy mental processes represent internal states orinteractions with external objects. (Philosophersrefer to this representational quality of the mindwith the confusing term intentionality.) This ar-gument is false.</p><p>The final negative contention is the reminderthat elucidating the emergence of the consciousmind depends on the existence of that same con-scious mind. Conducting an investigation withthe very instrument being investigated makesboth the definition of the problem and the ap-proach to a solution especially complicated. Giv-en the conflict between observer and observed,we are told, the human intellect is unlikely to beup to the task of comprehending how mindemerges from brain. This conflict is real, but thenotion that it is insurmountable is inaccurate.</p><p>In summary, the apparent uniqueness of theconscious-mind problem and the difficulties thatcomplicate ways to get at that problem generatetwo effects: they frustrate those researchers com-mitted to finding a solution and confirm the con-viction of others who intuitively believe that a so-lution is beyond our reach.</p><p>Evaluating the Difficulties</p><p>Those who cite the inability of research on theliving matter of the brain to reveal the sub-stance of mind assume that the current knowl-edge of that living matter is sufficient to makesuch judgment final. This notion is entirely unac-ceptable. The current description of neurobiologi-cal phenomena is quite incomplete, any way youslice it. We have yet to resolve numerous detailsabout the function of neurons and circuits at themolecular level; we do not yet grasp the behaviorof populations of neurons within a local brain re-gion; and our understanding of the large-scalesystems made up of multiple brain regions is alsoincomplete. We are barely beginning to addressthe fact that interactions among many noncon-tiguous brain regions probably yield highly com-plex biological states that are vastly more than thesum of their parts.</p><p>In fact, the explanation of the physics related tobiological events is still incomplete. Consequent-ly, declaring the conscious-mind problem insolu-ble because we have studied the brain to the hilt</p><p>114 SCIENTIFIC AMERICAN December 1999 How the Brain Creates the Mind</p><p>The brains businessis representing otherthings. Studies with</p><p>macaques show a remarkable fidelity</p><p>between a seen shape(a) and the shape of</p><p>the neural activitypattern (b) in one ofthe layers of the pri-</p><p>mary visual cortex.</p><p>a</p><p>b</p><p>DIM</p><p>ITRY</p><p> SC</p><p>HID</p><p>LOV</p><p>SKY;</p><p>SOU</p><p>RCE:</p><p>Too</p><p>tell </p><p>et a</p><p>l.,Jo</p><p>urna</p><p>l of N</p><p>euro</p><p>scie</p><p>nce,</p><p>May</p><p> 198</p><p>8.</p><p>Copyright 1999 Scientific American, Inc.</p></li><li><p>and have not found the mind is ludicrous. Wehave not yet fully studied either neurobiology orits related physics. For example, at the finest levelof description of mind, the swift construction,manipulation and superposition of many sensoryimages might require explanation at the quantumlevel. Incidentally, the notion of a possible role forquantum physics in the elucidation of mind, anidea usually associated with mathematical physi-cist Roger Penrose of the University of Oxford, isnot an endorsement of his specific proposals,namely, that consciousness is based on quantum-level phenomena occurring in the microtubulesconstituents of neurons and other cells. Thequantum level of operations might help explainhow we have a mind, but I regard it as unneces-sary to explain how we know that we own thatmindthe issue I regard as most critical for acomprehensive account of consciousness.</p><p>The strangeness of the conscious-mind prob-lem mostly reflects ignorance, which limits theimagination and has the curious effect of makingthe possible seem impossible. Science-fictionwriter Arthur C. Clarke has said, Any sufficientlyadvanced technology is indistinguishable frommagic. The technology of the brain is so com-plex as to appear magical, or at least unknow-able. The appearance of a gulf between mentalstates and physical/biological phenomena comesfrom the large disparity between two bodies ofknowledgethe good understanding of mind wehave achieved through centuries of introspectionand the efforts of cognitive science versus the in-complete neural specification we have achievedthrough the efforts of neuroscience. But there is noreason to expect that neurobiology cannot bridgethe gulf. Nothing indicates that we have reachedthe edge of an abyss that would separate, in prin-ciple, the mental from the neural.</p><p>Therefore, I contend that the biological process-es now presumed to correspond to mind process-es in fact are mind processes and will be seen to beso when understood in sufficient detail. I am notdenying the existence of the mind or saying thatonce we know what we need to know about biol-ogy the mind ceases to exist. I simply believe thatthe private, personal mind, precious and unique,indeed is biological and will one day be describedin terms both biological and mental.</p><p>The other main objection to an understandingof mind is that the real conflict between observerand observed makes the human intellect unfit tostudy itself. It is important, however, to point outthat the brain and mind are not a monolith: theyhave multiple structural levels, and the highest ofthose levels creates instruments that permit theobservation of the other levels. For example, lan-guage endowed the mind with the power to cate-gorize and manipulate knowledge according tological principles, and that helps us classify obser-vations as true or false. We should be modestabout the likelihood of ever observing our entirenature. But declaring defeat before we even make</p><p>the attempt defies Aristotles observationthat human beings are infinitely curiousabout their own nature.</p><p>Reasons for Optimism</p><p>My proposal for a solution to the co-nundrum of the conscious mind re-quires breaking the problem into twoparts. The first concern is how we generatewhat I call a movie-in-the-brain. Thismovie is a metaphor for the integratedand unified composite of diverse sensoryimagesvisual, auditory, tactile, olfactoryand othersthat constitutes the multime-dia show we call mind. The second issue isthe self and how we automatically gener-ate a sense of ownership for the movie-in-the-brain. The two parts of the problem arerelated, with the latter nested in the for-mer. Separating them is a useful researchstrategy, as each requires its own solution.</p><p>Neuroscientists have been attemptingunwittingly to solve the movie-in-the-brain part of the conscious-mind problemfor most of the history of the field. The en-deavor of mapping the brain regions in-volved in constructing the movie began al-most a century and a half ago, when PaulBroca and Carl Wernicke first suggestedthat different regions of the brain were in-volved in processing different aspects oflanguage. More recently, thanks to the ad-vent of ever more sophisticated tools, theeffort has begun to reap handsome rewards.</p><p>Researchers can now directly record theactivity of a single neuron or group of neu-rons and relate that activity to aspects of aspecific mental state, such as the percep-tion of the color red or of a curved line.Brain-imaging techniques such as PET(positron emission tomography) scansand fMR (functional magnetic resonance)scans reveal how different brain regions ina normal, living person are engaged by acertain mental effort, such as relating aword to an object or learning a particularface. Investigators can determine howmolecules within microscopic neuron circuits par-ticipate in such diverse mental tasks, and they canidentify the genes necessary for the productionand deployment of those molecules.</p><p>Progress in this field has been swift ever sinceDavid H. Hubel and Torsten Wiesel of HarvardUniversity provided the first clue for how braincircuits represent the shape of a given object, bydemonstrating that neurons in the primary visualcortex were selectively tuned to respond to edgesoriented in varied angles. Hubel and Margaret S.Livingstone, also at Harvard, later showed thatother neurons in the primary visual cortex re-spond selectively to color but not shape. AndSemir Zeki of University College London found</p><p>How the Brain Creates the Mind SCIENTIFIC AMERICAN December 1999 115</p><p>HA</p><p>NN</p><p>A D</p><p>AM</p><p>ASI</p><p>ONeuroscience continuesto associate specificbrain structures withspecific tasks. Somelanguage regions arehighlighted in a and b.Color-processing (red)and face-processing(green) regions areshown in c. Ones ownbody sense depends onthe region shown in d.</p><p>a</p><p>b</p><p>c</p><p>d</p><p>Copyright 1999 Scientific American, Inc.</p></li><li><p>that brain regions that received sensory informa-tion after the primary visual cortex did were spe-cialized for the further processing of color or move-ment. These results provided a counterpart to ob-servations made in living neurological patients:damage to distinct regions of the visual cortices in-terferes with color perception while leaving dis-cernment of shape and movement intact. </p><p>A large body of work, in fact, now points to theexistence of a correspondence between the struc-ture of an object as taken in by the eye and thepattern of neuron activity generated within thevisual cortex of the organism seeing that object[see illustration on page 114].</p><p>Further remarkable progress involving aspects ofthe movie-in-the-brain has led to increased in-sights related to mechanisms of learning andmemory. In rapid succession, research has revealedthat the brain uses discrete systems for differenttypes of learning. The basal ganglia and cerebel-lum are critical for the acquisition of skills, for ex-ample, learning to ride a bicycle or play a musicalinstrument; the hippocampus is integral to thelearning of facts pertaining to such entities as peo-ple, places or events. And once facts are learned,the long-term memory of those facts relies onmulticomponent brain systems, whose key partsare located in the vast brain expanses known ascerebral cortices.</p><p>Moreover, the process by which newly learnedfacts are consolidated in long-term memory goes</p><p>beyond properly working hippocampi and cere-bral cortices. Certain processes must take place, atthe level of neurons and molecules, so that theneural circuits are etched, so to speak, with theimpressions of a newly learned fact. This etchingdepends on strengthening or weakening the con-tacts between neurons, known as synapses. Aprovocative recent finding by Eric R. Kandel ofColumbia University and Timothy P. Tully ofCold Spring Harbor Laboratory is that etching theimpression requires the synthesis of fresh pro-teins, which in turn rely on the engagement ofspecific genes within the neurons charged withsuppo...</p></li></ul>