ON THE SEARCH FOR THE NEURAL CORRELATE OF CONSCIOUSNESS

David J. ChalmersPhilosophy ProgramResearch School of Social SciencesAustralian National University

I will discuss one aspect of the role that neuroscience plays in the search for a theory ofconsciousness. Whether or not neuroscience can solve all the problems of consciousnesssinglehandedly, it undoubtedly has a major role to play. Recent years have seen striking (notável)progress in neurobiological research bearing on the problems of consciousness. Theconceptual foundations of this sort of research, however, are only beginning to be laid (colocadas). I willlook at some of the things that are going on, from a philosopher’s perspective, and will try tosay something helpful about these foundations.We have all been hearing (ouvido) a lot about the “neural correlate of consciousness”. This phraseis intended to refer to the neural system or systems primarily associated with consciousexperience. The acronym of the day is “NCC” – Neurais correlatos consciência. We all have an NCC inside our head, we justhave to find out what it is. In recent years we have seen quite a few proposals about theidentity of the NCC. One of the most famous proposals is Crick and Koch’s suggestionconcerning 40-hertz oscillations. That proposal has since faded (desaparecido aos poucos) away a little but there are allsorts of other suggestions out there. The picture is almost reminiscent of particle physics,where they have something like 236 particles and people talk about the “particle zoo”. Instudying consciousness, one might talk about the “neural correlate zoo”.A brief list of suggestions that have been put forward includes:

40-hertz oscillations in the cerebral cortex (Crick and Koch 1990).Intralaminar nucleus in the thalamus (Bogen 1995).Re-entrant loops in thalamocortical systems (Edelman 1989).40-hertz rhythmic activity in thalamocortical systems (Llinas et al 1994).Nucleus reticularis (Taylor and Alavi 1995).This paper appears in Toward a Science of Consciousness II: The Second Tucson Discussions and Debates (S. Hameroff, A. Kaszniak, and A.Scott, eds), published with MIT Press in 1998. It is a transcript of my talk at the second Tucson conference in April 1996, lightly edited to include the contents of overheads and to exclude some diversions with a consciousness meter. A more in-depth argument for some of the claims in this paper can be found in Chapter 6 of my book The Conscious Mind (Chalmers, 1996).

Extended reticular-thalamic activation system (Newman and Baars 1993).Anterior cingulate system (Cotterill 1994).Neural assemblies bound by NMDA (Flohr 1995).Temporally-extended neural activity (Libet 1994).Back-projections to lower cortical areas (Cauller and Kulics 1991).Visual processing within the ventral stream (Milner and Goodale 1995).Neurons in visual cortex projecting to prefrontal areas (Crick and Koch 1995).Neural activity in area V5 (Tootell et al 1995).Certain neurons in the superior temporal sulcus and inferior temporal cortex(Logothetis and Schall 1989, Sheinberg and Logothetis 1997).Neuronal gestalts in an epicenter (Greenfield 1995).

Outputs of a comparator system in the hippocampus (Gray 1995).Quantum coherence in microtubules (Hameroff 1994).Global workspace (Baars 1988).High-quality representations (Farah 1994).Selector inputs to action systems (Shallice 1988).

The list includes a few “cognitive correlates” of consciousness (CCC?) but the generalidea is similar. We find some intriguing commonalities among the proposals in this list. Anumber of them give a major role to interactions between the thalamus and the cortex, forexample. All the same, the great number and diversity of the proposals can be overwhelming.I propose to step back and try to make sense of all this activity by asking some foundationalquestions.A primary question is this: how can one search for the neural correlate of consciousness?As we all know, measuring consciousness is problematic. The phenomenon is not directly andstraightforwardly observable. It would be much easier if we had a way of getting atconsciousness directly—if we had, for example, a consciousness meter.If we had such an instrument, searching for the NCC would be straightforward. Wewould wave the consciousness meter and measure a subject’s consciousness directly. At thesame time, we would monitor the underlying brain processes. After a number of trials, wewould say such-and-such brain processes are correlated with experiences of various kinds, sothere is the neural correlate of consciousness.Alas, we have no consciousness meter, and for principled reasons it seems we cannothave one. Consciousness just is not the sort of thing that can be measured directly. What,then, do we do without a consciousness meter? How can the search go forward? How does allthis experimental research proceed?2I think the answer is this: we get there with principles of interpretation, by which weinterpret physical systems to judge the presence of consciousness. We might call these pre-experimental bridging principles. They are the criteria that we bring to bear in looking atsystems to say (1) whether or not they are conscious now, and (2) which information they areconscious of, and which they are not. We cannot reach in directly and grab those experiences,so we rely on external criteria instead.That is a perfectly reasonable thing to do. But something interesting is going on. Theseprinciples of interpretation are not themselves experimentally determined or experimentallytested. In a sense they are pre-experimental assumptions. Experimental research gives us a lotof information about processing; then we bring in the bridging principles to interpret theexperimental results, whatever those results may be. They are the principles by which wemake inferences from facts about processing to facts about consciousness, and so they areconceptually prior to the experiments themselves. We cannot actually refine themexperimentally (except perhaps by first-person experimentation!), because we have noindependent access to the independent variable. Instead, these principles will be based onsome combination of (1) conceptual judgments about what counts as a conscious process, and(2) information gleaned from our first-person perspective on our own consciousness.I think we are all stuck in this boat. The point applies whether one is a reductionist or ananti-reductionist about consciousness. A hard-line reductionist might put some of these pointsa little differently, but either way the experimental work will require pre-experimentalreasoning to determine the criteria for ascribing consciousness. Of course such principles areusually left implicit in empirical research. We do not usually see papers saying “Here is thebridging principle, here are the data, and here is what follows.” But it is useful to make themexplicit. The very presence of these principles has strong and interesting consequences in thesearch for the NCC.In a sense, in relying on these principles we are taking a leap into the epistemological

unknown. Because we do not measure consciousness directly, we have to make something ofa leap of faith. It may not be a big leap, but nevertheless it suggests that everyone doing thiswork is engaged in philosophical reasoning. Of course one can always choose to stay on solidground, talking about the empirical results in a neutral way, but the price of doing so is thatone gains no particular insight into consciousness. Conversely, as soon as we draw anyconclusions about consciousness, we have gone beyond the information given. So we need topay careful attention to the reasoning involved.What are these principles of interpretation? The first and by far the most prevalent is theprinciple of verbal report. When someone says “Yes, I see that table now”, we infer that they3are conscious of the table. When someone says “Yes, I see red now”, we infer that they arehaving an experience of red. Of course one might always say “How do you know?”—aphilosopher might suggest that we may be faced with a fully functioning zombie—but in factmost of us do not believe that the people around us are zombies, and in practice we are quiteprepared to rely on this principle. As pre-experimental assumptions go, this one is relativelysafe—it does not require a huge leap of faith—and it is very widely used.The principle here is that when information is verbally reported, it is conscious. One canextend this principle slightly, for no one believes an actual verbal report is required forconsciousness; we are conscious of much more than we report on any given occasion. Thus anextended principle might say that when information is directly available for verbal report, it isconscious.Experimental researchers do not rely only on these principles of verbal report andreportability. The principles can be somewhat limiting when we want to do broaderexperiments. In particular, we do not want to restrict our studies of consciousness to subjectsthat have language. In fact, at this conference we saw a beautiful example of research onconsciousness in language-free creatures. I refer to the work by Nikos Logothetis and hiscolleagues (e.g., Logothetis and Schall 1989; Leopold and Logothetis 1996, Sheinberg andLogothetis 1997). This work uses experiments on monkeys to draw conclusions about theneural processes associated with consciousness. How do Logothetis et al manage to drawconclusions about a monkey’s consciousness without getting any verbal reports? They rely onthe monkey pressing bars: if the monkey can be made to press a bar in an appropriate way inresponse to a stimulus, we can say that that stimulus was consciously perceived.The criterion at play seems to be require that the information be available for an arbitraryresponse. If it turned out that the monkey could press a bar in response to a red light but coulddo nothing else, we would be tempted to say that it was not a case of consciousness at all, butsome sort of subconscious connection. If on the other hand we find information that isavailable for response in all sorts of different ways, then we will say that it is conscious.The underlying general principle is something like this: When information is directlyavailable for global control in a cognitive system, then it is conscious. If information isavailable for response in many motor modalities, we will say it is conscious, at least in arange of relatively familiar systems such as humans, other primates and so on. This principlesquares well with the preceding one, when the capacity for verbal report is present:availability for verbal report and availability for global control seem to go together in suchcases (report is one of the key aspects of control, after all, and it is rare to find information4that is reportable but not available more widely). But this principle is also applicable whenlanguage is not present.A correlation between consciousness and global availability (for short) seems to fit thefirst-person evidence—that gleaned from our own conscious experience—quite well. Wheninformation is present in my consciousness, it is generally reportable, and it can generally bebrought to bear in controlling behavior in all sorts of ways. I can talk about it, I can point inthe general direction of a stimulus, I can press bars, and so on. Conversely, when we find

information that is directly available in this way for report and other aspects of control, it isgenerally conscious information. One can bear out this idea by considering cases.There are some tricky puzzle cases to consider, such as blindsight, where one has someavailability for control but arguably no conscious experience. Those cases might best behandled by invoking the directness criterion: insofar as the information here is available forreport and other control processes at all, the availability is indirect by comparison to the directand automatic availability in standard cases. One might also stipulate that it is availability forvoluntary control that is relevant, to deal with cases of involuntary unconscious response,although that is a complex issue. I discuss a number of puzzle cases in more detail elsewhere(Chalmers 1997), where I also give a much more detailed defense of the idea that somethinglike global availability is the key pre-empirical criterion for the ascription of consciousness.But this principle remains at best a first-order approximation of the functional criteriathat come into play. I am less interested today in getting all the fine details right than inexploring the consequences of the idea that some such functional criterion is required and isimplicit in all the empirical research on the neural correlate of consciousness. If you disagreewith the criterion I have suggested—presumably because you can think of counterexamples—you may want to use those examples to refine it or to come up with a better criterion of yourown. The crucial point is that in the very act of experimentally distinguishing conscious fromunconscious processes, some such criterion is always at play.My question is: If something like this is right, then what follows? That is, if some suchbridging principles are implicit in the methodology for the search for the NCC, then what arethe consequences? I will use global availability as my main functional criterion in thisdiscussion, but many of the points should generalize.The first thing one can do is produce what philosophers might call a rationalreconstruction of the search for the neural correlate of consciousness. With a rationalreconstruction we can say: Maybe things do not work exactly like this in practice, but therational underpinnings of the procedure have something like this form. That is, if one were totry to justify the conclusions one has reached as well as possible, one’s justification would5follow the shape of the rational reconstruction. In this case, a rational reconstruction mightlook something like this:(1)(2)so(3)Consciousness <-> neural process N (conclusion).Consciousness <-> global availability (bridging principle)Global availability <-> neural process N (empirical work)According to this reconstruction, one implicitly embraces some sort of pre-experimentalbridging principle that one finds plausible on independent grounds, such as conceptual orphenomenological grounds. Then one does the empirical research. Instead of measuringconsciousness directly, we detect the functional property. We see that when this functionalproperty (e.g., global availability) is present, it is correlated with a specific neural process(e.g., 40-hertz oscillations). Combining the pre-empirical premise and the empirical result, wearrive at the conclusion that this neural process is a candidate for the NCC.Of course it does not work nearly so simply in practice. The two stages are highlyintertwined; our pre-experimental principles may themselves be refined as experimentalresearch goes along. Nevertheless I think one can make a separation into pre-empirical andexperimental components for the sake of analysis. With this rational reconstruction in hand,what sort of conclusions follow? I want to draw out about six consequences here.(1) The first conclusion is a characterization of the neural correlates of consciousness. Ifthe NCC is arrived at via this methodology, then whatever it turns out to be, it will be a

mechanism of global availability. The presence of the NCC wherever global availability ispresent suggests that it is a mechanism that subserves global availability in the brain. The onlyalternative is that it might be a symptom rather than a mechanism of global availability; but inprinciple that possibility ought to be addressable by dissociation studies, lesioning, and so on.If a process is a mere symptom of availability, we ought to be able to empirically dissociate itfrom global availability while leaving the latter intact. The resulting data would suggest to usthat consciousness can be present even when the neural process in question is not, thusindicating that it was not a perfect correlate of consciousness after all.(A related line of reasoning supports the idea that a true NCC must be a mechanism ofdirect availability for global control. In principle, mechanisms of indirect availability willdissociable from the empirical evidence for consciousness, for example by directlystimulating the mechanisms of direct availability. The indirect mechanisms will be “screened6off” by the direct mechanisms in much the same way as the retina is screened off as an NCCby the visual cortex.)In fact, if one looks at the various proposals, this template seems to fit them pretty well.For example, the 40-hertz oscillations discussed by Crick and Koch were put forwardprecisely because of the role they might have in binding and integrating information intoworking memory, and working memory is of course a major mechanism whereby informationis made available for global control in a cognitive system. Similarly, it is plausible thatLibet’s extended neural activity is relevant precisely because the temporal extendedness ofactivity gives certain information the capacity to dominate later processes that lead to control.Baars’ global workspace is a particularly explicit example of such a mechanism; it is putforward explicitly as a mechanism whereby information can be globally disseminated. Allthese mechanisms and many of the others seem to be candidates for mechanisms of globalavailability in the brain.(2) This reconstruction suggests that a full story about the neural processes associatedwith consciousness will do two things. First, it will explain global availability in the brain.Once we know all about the relevant neural processes, we will know precisely howinformation is made directly available for global control in the brain, and this will be anexplanation in the full sense. Global availability is a functional property, and as always theproblem of explaining the a function’s performance is a problem to which mechanisticexplanation is well-suited. So we can be confident that in a century or two global availabilitywill be straightforwardly explained. Second, this explanation of availability will do somethingelse: It will isolate the processes that underlie consciousness itself. If the bridging principle isgranted, then mechanisms of availability will automatically be correlates of phenomenologyin the full sense.Now, I do not think this is a full explanation for consciousness. One can always ask whythese processes of availability should give rise to consciousness in the first place. As yet wecannot explain why they do so, and it may well be that full details about the processes ofavailability will still fail to answer this question. Certainly, nothing in the standardmethodology I have outlined answers the question; that methodology assumes a relationbetween availability and consciousness, and therefore does nothing to explain it. Therelationship between the two is instead taken as something of a primitive. So the hard problemremains. But who knows: Somewhere along the line we may be led to the relevant insightsthat show why the link is there, and the hard problem may then be solved. In the meantime,whether or not we have solved the hard problem, we may nevertheless have isolated the basis7for consciousness in the brain. We just have to keep in mind the distinction betweencorrelation and explanation.(3) Given this paradigm, it is likely that there will be many neural correlates ofconsciousness. This suggestion is unsurprising, but the rational reconstruction illustrates just

why such a multiplicity of correlates should exist. There will be many neural correlates ofconsciousness because there will be many mechanisms of global availability. There will bemechanisms in different modalities: the mechanisms of visual availability may be quitedifferent from the mechanisms of auditory availability, for example. (Of course they may bethe same, in that we could find a later area that would integrate and disseminate all thisinformation, but that is an open question.) There will also be mechanisms at different stagesin the processing path whereby information is made globally available: early mechanisms andlater ones. All these may be candidates for the NCC. And we will find mechanisms at manylevels of description: for example, 40-hertz oscillations may well be redescribed as high-quality representations, or as part of a global workspace, at a different level of description. Itmay therefore turn out that a number of the animals in the zoo, so to speak, can co-existbecause they are compatible in one of these ways.I will not speculate much further on just what the neural correlates of consciousness are.No doubt some of the ideas in the initial list will prove to be entirely off the track, and someof the others will prove closer to the mark. But I hope the conceptual issues are becomingclearer.(4) This way of thinking about things allows one to make sense of a idea that issometimes floated: that of a consciousness module. Sometimes this notion is disparaged;sometimes it is embraced. But the methodology in the search for an NCC suggests that it is atleast possible that there could turn out to be such a module. What would it take? It wouldrequire some sort of functionally localizable, internally integrated area, through which allglobal availability runs. It need not be anatomically localizable, but to qualify as a module itwould need to be localizable in some broader sense. For example, the parts of the modulewould have to have high-bandwidth communication among themselves, compared to therelatively low-bandwidth communication that they have with other areas. Such a thing couldturn out to exist. It does not strike me as especially likely that things will turn out this way; itseems just as likely that we will find multiple independent mechanisms of global availabilityin the brain, scattered around without much mutual integration. If that is the result, we willprobably say that there is no consciousness module after all. But that is another of thoseempirical questions.8If something like this module did turn out to exist in the brain, it would resemble Baars’conception of a global workspace: a functional area responsible for integrating information inthe brain and disseminating it to multiple nonconscious specialized processes. In fact, manyof the ideas I put forward here are compatible with things that Baars has been saying for yearsabout the role of global availability in the study of consciousness. Indeed, this way of lookingat things suggests that some of his ideas are almost forced on us by the methodology. Thespecial epistemological role of global availability helps explain why the idea of a globalworkspace is a useful way of thinking about almost any empirical proposal aboutconsciousness. If NCCs are identified as such precisely because of their role in global control,then at least on a first approximation, we should expect the global workspace idea to be anatural fit.(5) We can also apply this picture to a question that has been discussed frequently at thisconference: Are the neural correlates of visual consciousness to be found in V1, in theextrastriate visual cortex, or elsewhere? If our picture of the methodology is correct, then theanswer presumably will depend on which visual area is most directly implicated in globalavailability.Crick and Koch have suggested that the visual NCC is not to be found within V1,because V1 does not contain neurons that project to the prefrontal cortex. This reasoning hasbeen criticized by Ned Block for conflating access consciousness and phenomenalconsciousness (see Block, this volume); but interestingly, the picture I have developedsuggests that it may be good reasoning. The prefrontal cortex is known to be associated with

control processes; so if a given area in the visual cortex projects to prefrontal areas, then itmay well be a mechanism of direct availability. And if it does not project in this way, it is lesslikely to be such a mechanism; at best it might be indirectly associated with globalavailability. Of course we still have plenty of room to raise questions about the empiricaldetails. But the broader point is that for the sort of reasons discussed in (2) above, it is likelythat the neural processes involved in explaining access consciousness will simultaneously beinvolved in a story about the basis of phenomenal consciousness. If something like this idea isimplicit in their reasoning, Crick and Koch might escape the charge of conflation. Of coursethe reasoning depends on these somewhat shaky bridging principles, but then all work on theneural correlates of consciousness must appeal to such principles somewhere, so thislimitation cannont be held against Crick and Koch in particular.(6) Sometimes the neural correlate of consciousness is conceived of as the Holy Grail fora theory of consciousness. It will make everything fall into place. For example, once we9discover the NCC, then we will have a definitive test for consciousness, enabling us todiscover consciousness wherever it arises. That is, we might use the neural correlate itself as asort of consciousness meter. If a system has 40-hertz oscillations (say), then it is conscious; ifit has none, then it is not conscious. Or if a thalamocortical system turns out to be the NCC,then a system without such a system is unlikely to be conscious. This sort of reasoning is notusually put quite so baldly, but I think one finds some version of it quite frequently.This reasoning can be tempting, but one should not succumb to the temptation. Given thevery methodology that comes into play here, we have no way of definitely establishing agiven NCC as an independent test for consciousness. The primary criterion for consciousnesswill always remain the functional property we started with: global availability, or verbalreport, or whatever. That is how we discovered the correlations in the first place. 40-hertzoscillations (or whatever) are relevant only because of their role in satisfying this criterion.True, in cases where we know that this association between the NCC and the functionalproperty is present, the NCC might itself function as a sort of “signature” of consciousness,but once we dissociate the NCC from the functional property, all bets are off. To take anextreme example: If we have 40-hertz oscillations in a test tube, that condition almostcertainly will not yield consciousness. But the point applies equally in less extreme cases.Because it was the bridging principles that gave us all the traction in the search for an NCC inthe first place, it is not clear that anything follows in cases where the functional criterion isthrown it away. So there is no free lunch here: one cannot get something for nothing.Once we recognize the central role of pre-experimental assumptions in the search for theNCC, we realize that there are limitations on just what we can expect this search to tell us.Still, whether or not the NCC is the Holy Grail, I hope that I have said enough to make it clearthat the quest for it is likely to enhance our understanding considerably. And I hope to havemade a case that philosophy and neuroscience can come together to help clarify some of thedeep problems involved in the study of consciousness.10BibliographyBaars, B.J. 1988. A Cognitive Theory of Consciousness. Cambridge: Cambridge UniversityPress.Bogen, J.E. 1995. On the neurophysiology of consciousness, parts I and II. Consciousnessand Cognition, 4:52-62 & 4:137-58.Cauller, L.J. & Kulics, A.T. 1991. The neural basis of the behaviorally relevant N1component of the somatosensory evoked potential in awake monkeys: Evidence thatbackward cortical projections signal conscious touch sensation. Experimental BrainResearch 84:607-619.Chalmers, D.J. 1996. The Conscious Mind: In Search of a Fundamental Theory. Oxford:Oxford University Press.

Chalmers, D.J. 1997. Availability: the cognitive basis of experience? Behavioral and BrainSciences 20: 148-9. Also in N. Block, O. Flanagan, & G. Güzeldere (eds) The Nature ofConsciousness (MIT Press, 1997).Cotterill, R. 1994. On the unity of conscious experience. Journal of Consciousness Studies 2:290-311.Crick, F. and Koch, C. 1990. Towards a neurobiological theory of consciousness. Seminars inthe Neurosciences 2: 263-275.Crick, F. & Koch, C. 1995. Are we aware of neural activity in primary visual cortex? Nature375: 121-23.Edelman, G.M. 1989. The Remembered Present: A Biological Theory of Consciousness. NewYork: Basic Books.Farah, M.J. 1994. Visual perception and visual awareness after brain damage: A tutorialoverview. In (C. Umilta and M. Moscovitch, eds.) Consciousness and UnconsciousInformation Processing: Attention and Performance 15. Cambridge: MIT Press.Flohr, H. 1995. Sensations and brain processes. Behavioral Brain Research 71: 157-61.Gray, J.A. 1995. The contents of consciousness: A neuropsychological conjecture. Behavioraland Brain Sciences 18: 659-722.Greenfield, S. 1995. Journey to the Centers of the Mind. New York: W.H. Freeman.Hameroff, S.R. 1994. Quantum coherence in microtubules: A neural basis for emergentconsciousness? Journal of Consciousness Studies 1: 91-118.Leopold, D.A. & Logothetis, N.K. 1996. Activity-changes in early visual cortex reflectmonkeys’ percepts during binocular rivalry. Nature 379: 549-553.Libet, B. 1993. The neural time factor in conscious and unconscious events. In Experimentaland Theoretical Studies of Consciousness (Ciba Foundation Symposium 174). New York:Wiley.Llinas, R.R., Ribary, U., Joliot, M. & Wang, X.-J. 1994. Content and context in temporalthalamocortical binding. In (G. Buzsaki, R.R. Llinas, & W. Singer, eds.) Temporal Codingin the Brain. Berlin: Springer Verlag.Logothetis, N. & Schall, J. 1989. Neuronal correlates of subjective visual perception. Science245: 761-63.11Milner, A.D., and Goodale, M. A. 1995. The Visual Brain in Action. Oxford: OxfordUniversity Press.Shallice, T. 1988. Information-processing models of consciousness: possibilities andproblems. In (A. Marcel and E. Bisiach, eds.) Consciousness in Contemporary Science.Oxford: Oxford University Press.Sheinberg, D. L. and Logothetis, N.K. 1997. The role of temporal cortical areas in perceptualorganization. Proceedings of the National Academy of Sciences USA 94: 139-141.Taylor, J.G. & Alavi, F.N. 1993. Mathematical analysis of a competitive network forattention. In (J.G. Taylor, ed.) Mathematical Approaches to Neural Networks. New York:Elsevier.Tootell, R.B., Reppas, J.B., Dale, A.M., Look, R.B., Sereno, M.I., Malach, R., Brady, J. &Rosen, B.R. 1995. Visual motion aftereffect in human cortical area MT revealed byfunctional magnetic resonance imaging. Nature 375:139-41.

Na pesquisa para o correlato neural da Consciência [*]

David J. Chalmers David J. Chalmers

Department of Philosophy Departamento de Filosofia University of Arizona Universidade do Arizona Tucson, AZ 85721 Tucson, AZ 85721

chalmers@arizona.edu chalmers@arizona.edu

*[[ This paper appears in Toward a Science of Consciousness II: The Second Tucson Discussions and Debates (S. Hameroff, A. Kaszniak, and A.Scott, eds), published with MIT Press in 1998. * [[Este papel aparece em direção a uma ciência da Consciência II: The Second Tucson Discussões e Debates (S. Hameroff, A. Kaszniak e A. Scott, eds), publicado com MIT Press em 1998. It is a transcript of my talk at the second Tucson conference in April 1996, lightly edited to include the contents of overheads and to exclude some diversions with a consciousness meter. É uma transcrição da minha palestra na conferência de Tucson segunda em abril de 1996, ligeiramente editado para incluir o conteúdo de despesas gerais e excluir algumas diversões com um medidor de consciência. A more in-depth argument for some of the claims in this paper can be found in Chapter 6 of my book The Conscious Mind (Chalmers, 1996). ]] Um argumento mais em profundidade para algumas das reivindicações neste documento podem ser encontradas no Capítulo 6 do meu livro A Mente Consciente (Chalmers, 1996).]]

I'm going to talk about one aspect of the role that neuroscience plays in the search for a theory of consciousness. Eu vou falar sobre um aspecto do papel que desempenha na neurociência a busca de uma teoria da consciência. Whether or not neuroscience can solve all the problems of consciousness singlehandedly, there is no question that it has a major role to play. Ou não a neurociência pode resolver todos os problemas de consciência sozinho, não há dúvida de que ele tem um papel importante a desempenhar. We've seen at this conference that there's a vast amount of progress in neurobiological research, and that much of it is clearly bearing on the problems of consciousness. Vimos nesta conferência que há uma grande quantidade de progresso na pesquisa neurobiológica, e que muito do que é claramente influência sobre os problemas de consciência. But the conceptual foundations of this sort of research are only beginning to be laid. Mas os fundamentos conceituais deste tipo de pesquisa estão apenas começando a ser estabelecidas. So I will look at some of the things that are going on from a philosopher's perspective and will see if there's anything helpful to say about these foundations. Então eu vou olhar para algumas das coisas que estão acontecendo do ponto de vista de um filósofo e verá se há algo útil a dizer sobre essas fundações.

We've all been hearing a lot about the "neural correlate of consciousness". Todos nós temos ouvido muito sobre o "correlato neural da consciência". This phrase is intended to refer to the neural system or systems primarily associated with conscious experience. Esta frase é usado para se referir ao sistema neural ou sistemas principalmente associada com a experiência consciente. I gather that the catchword of the day is "NCC". Percebi que a palavra de ordem do dia é "NCC". We all have an NCC inside our head, we just have to find out what it is. Todos nós temos um NCC dentro de nossa cabeça, só temos de descobrir o que é. In recent years there have been quite a few proposals about the identity of the NCC. Nos últimos anos tem havido várias propostas sobre a identidade do NCC. One of the most famous proposals is Crick and Koch's suggestion concerning 40-hertz oscillations. Uma das propostas mais famosa é a sugestão de Crick e Koch a respeito de 40 hertz oscilações. That proposal has since faded away a little but there are all sorts of other suggestions out there. Que a proposta, desde então, desapareceu um pouco, mas há toda uma série de sugestões de outros lá fora. It's almost got to a point where it's reminiscent of particle physics, where they have something like 236 particles and people talk about the "particle zoo". É quase chegou a um ponto onde é reminiscente da física de partículas, onde eles têm algo como 236 partículas e as pessoas falam sobre o "zoo de partículas". In the study of consciousness, one might talk about the "neural correlate zoo". No estudo da consciência, pode-se falar sobre o "zoo correlacionar neural". There have also been a number of related proposals about what we might call the "cognitive correlate of consciousness" (CCC?). Houve também uma série de propostas relacionadas com o que poderíamos

chamar de "cognitiva correlato da consciência" (CCC?).

A small list of suggestions that have been put forward might include: Uma pequena lista de sugestões que foram apresentadas podem incluir:

40-hertz oscillations in the cerebral cortex (Crick and Koch 1990) 40 hertz oscilações no córtex cerebral (Crick e Koch 1990)

Intralaminar nucleus in the thalamus (Bogen 1995) Núcleo intralaminar no tálamo (Bogen 1995)

Re-entrant loops in thalamocortical systems (Edelman 1989) Reentrante laços em sistemas tálamo-cortical (Edelman 1989)

40-hertz rhythmic activity in thalamocortical systems (Llinas et al 1994) 40 hertz atividade rítmica em sistemas tálamo-cortical (Llinas et al 1994)

Nucleus reticularis (Taylor and Alavi 1995) Núcleo reticular (Taylor e Alavi 1995) Extended reticular-thalamic activation system (Newman and Baars 1993) Sistema de

ativação reticular estendeu-tálamo (Newman e Baars 1993) Anterior cingulate system (Cotterill 1994) Sistema cingulado anterior (Cotterill 1994) Neural assemblies bound by NMDA (Flohr 1995) Assembléias neurais vinculado por

NMDA (Flohr 1995) Temporally-extended neural activity (Libet 1994) Temporalmente prolongada atividade

neural (Libet 1994) Backprojections to lower cortical areas (Cauller and Kulics 1991) Backprojections para

diminuir as áreas corticais (Cauller e Kulics 1991) Neurons in extrastriate visual cortex projecting to prefrontal areas (Crick and Koch 1995)

Neurônios no córtex visual extra-estriado projetando-se para áreas pré-frontais (Crick e Koch 1995)

Neural activity in area V5/MT (Tootell et al 1995) Atividade neural na área V5/MT (Tootell et al 1995)

Certain neurons in the superior temporal sulcus (Logothetis and Schall 1989) Certos neurônios no sulco temporal superior (Logothetis e Schall 1989)

Neuronal gestalts in an epicenter (Greenfield 1995) Gestalts neuronal em um epicentro (Greenfield, 1995)

Outputs of a comparator system in the hippocampus (Gray 1995) Saídas de um sistema de comparação no hipocampo (Gray, 1995)

Quantum coherence in microtubules (Hameroff 1994) Coerência quântica nos microtúbulos (Hameroff 1994)

Global workspace (Baars 1988) Global de espaço de trabalho (Baars, 1988) Activated semantic memories (Hardcastle 1995) Ativadas memórias semântica (Hardcastle

1995) High-quality representations (Farah 1994) Alta qualidade representações (Farah 1994) Selector inputs to action systems (Shallice 1988) Insumos seletor para sistemas de ação

(Shallice 1988)

There are a few intriguing commonalities among the proposals on this list. Há alguns pontos comuns entre as propostas intrigante nesta lista. A number of them give a central role to interactions between the thalamus and the cortex, for example. Alguns deles dão um papel central às interações entre o tálamo eo córtex, por exemplo. All the same, the sheer number and diversity of the proposals can be a little overwhelming. Tudo a mesma coisa, o grande número e diversidade das propostas pode ser um pouco esmagadora. I propose to step back a little and try to make sense of all this activity by asking some foundational questions. Proponho-me voltar um pouco e tentar dar sentido a toda essa atividade fazendo algumas perguntas fundamentais.

A central question is this: how is it, in fact, that one can search for the neural correlate of consciousness? A questão central é esta: como é que é, de fato, que se pode procurar o correlato neural da consciência? As we all know, there are problems in measuring consciousness. Como todos

sabemos, existem problemas na medição da consciência. It's not a directly and straightforwardly observable phenomenon. Não é um fenômeno diretamente e sem observável. It would be a lot easier if we had a way of getting at consciousness directly; if we had, for example, a consciousness meter. Seria muito mais fácil se tivéssemos uma forma de chegar a consciência diretamente, se tivéssemos, por exemplo, um medidor de consciência.

If we had a consciousness meter, searching for the NCC would be straightforward. Se tivéssemos um medidor de consciência, procurando o NCC seria simples. We'd wave the consciousness meter and measure a subject's consciousness directly. Nós tínhamos consciência de onda do medidor e medir a consciência de um sujeito diretamente. At the same time, we'd monitor the underlying brain processes. Ao mesmo tempo, a gente acompanhar os processos cerebrais subjacentes. After a number of trials, we'd say OK, such-and-such brain processes are correlated with experiences of various kinds, so that's the neural correlate of consciousness. Após uma série de ensaios, nós diríamos OK, tais processos e tal cérebro estão correlacionados com as experiências de vários tipos, de modo que é o correlato neural da consciência.

Alas, we don't have a consciousness meter, and there seem to be principled reasons why we can't have one. Infelizmente, não temos um medidor de consciência, e parece haver razões de princípio porque nós não podemos ter um. Consciousness just isn't the sort of thing that can be measured directly. Consciência não é apenas o tipo de coisa que pode ser medido diretamente. So: What do we do without a consciousness meter? Então: O que vamos fazer sem um metro consciência? How can the search go forward? Como pode a busca avançar? How does all this experimental research proceed? Como é que toda essa pesquisa experimental proceder?

I think the answer is this: we get there through principles of interpretation . Acho que a resposta é esta: vamos chegar lá através de princípios de interpretação. These are principles by which we interpret physical systems to judge whether or not they have consciousness. Estes são princípios pelos quais nós interpretamos sistemas físicos para avaliar se têm ou não consciência. We might call these pre-experimental bridging principles . Poderíamos chamar estes princípios pré-experimental ponte. These are the criteria that we bring to bear in looking at systems to say (a) whether or not they are conscious now, and (b) what information they are conscious of, and what information they are not. Estes são os critérios que trazemos para ter em olhar para os sistemas de dizer (a) ou não estão conscientes agora, e (b) as informações que eles estão conscientes de, e as informações que eles não são. We can't reach in directly and grab those experiences and "transpersonalize" them into our own, so we rely on external criteria instead. Não podemos chegar diretamente no e agarrar essas experiências e "transpersonalize"-los em nosso próprio, por isso contamos com critérios externos vez.

That's a perfectly reasonable thing to do. Isso é uma coisa perfeitamente razoável a fazer. But in doing this we have to realize that something interesting is going on. Mas ao fazer isso, temos de perceber que algo interessante está acontecendo. These principles of interpretation are not themselves experimentally determined or experimentally tested. Estes princípios de interpretação não são eles próprios determinados experimentalmente ou testadas experimentalmente. In a sense they are pre-experimental assumptions. Em certo sentido, eles são suposições pré-experimentais. Experimental research gives us a lot of information about processing; then we bring in the bridging principles to interpret the experimental results, whatever those results may be. Pesquisa experimental nos dá muitas informações sobre o processamento, em seguida, trazemos os princípios de extrapolação para interpretar os resultados experimentais, o que quer que esses resultados podem ser. They are the principles by which we make inferences from facts about processing to facts about consciousness, so they are conceptually prior to the experiments themselves. Eles são os princípios pelos quais fazemos inferências a partir de fatos sobre o processamento de fatos sobre a consciência, então eles são conceitualmente antes dos experimentos si. We can't actually refine them experimentally (except perhaps through first-person experimentation!), because we don't have any independent access to the independent variable. Nós não podemos realmente refiná-los experimentalmente (exceto talvez através da experimentação em primeira pessoa!), Porque não

temos qualquer acesso independente para a variável independente. Instead, these principles will be based on some combination of (a) conceptual judgments about what counts as a conscious process and (b) information gleaned from our first-person perspective on our own consciousness. Em vez disso, estes princípios será baseado em uma combinação de (a) julgamentos conceitual sobre o que conta como um processo consciente e (b) informação recolhida a partir de nossa perspectiva em primeira pessoa sobre a nossa própria consciência.

I think we are all stuck in this boat. Acho que estamos todos presos nesse barco. The point applies whether one is a reductionist or an anti-reductionist about consciousness. O ponto aplica-se se alguém é um reducionista ou um anti-reducionista sobre a consciência. A hard-line reductionist might put some of these points slightly differently, but either way, the experimental work is going to require pre-experimental reasoning to determine the criteria for ascription of consciousness. A reducionista linha-dura pode colocar alguns desses pontos de forma ligeiramente diferente, mas de qualquer forma, o trabalho experimental vai exigir pré-experimental de raciocínio para determinar os critérios para atribuição de consciência. Of course such principles are usually left implicit in empirical research. É claro que tais princípios são geralmente deixado implícito na pesquisa empírica. We don't usually see papers saying "Here is the bridging principle, here are the data, and here is what follows." Nós não costumamos ver papéis dizendo: "Aqui é o princípio ponte, aqui estão os dados, e aqui está o que se segue." But it's useful to make them explicit. Mas é útil para torná-los explícitos. The very presence of these principles has some strong and interesting consequences in the search for the NCC. A presença destes princípios tem algumas conseqüências forte e interessante em busca do NCC.

In a sense, in relying on these principles we are taking a leap into the epistemological unknown. Em certo sentido, em confiar nesses princípios estamos dando um salto para o desconhecido epistemológica. Because we don't measure consciousness directly, we have to make something of a leap of faith. Porque não medimos a consciência diretamente, nós temos que fazer algo de um salto de fé. It may not be a big leap, but nevertheless it suggests that everyone doing this sort of work is engaged in philosophical reasoning. Pode não ser um grande salto, mas, no entanto, sugere que toda a gente a fazer este tipo de trabalho está envolvida no raciocínio filosófico. Of course one can always choose to stay on solid ground, talking about the empirical results in a neutral way; but the price of doing so is that one gains no particular insight into consciousness. É claro que sempre se pode optar por ficar em terra firme, falando sobre os resultados empíricos de forma neutra, mas o preço de fazer isso é que se ganha nenhum insight especial na consciência. Conversely, as soon as we draw any conclusions about consciousness, we have gone beyond the information given, so we need to pay careful attention to the reasoning involved. Por outro lado, assim que tirar quaisquer conclusões sobre a consciência, temos ido além da informação dada, por isso precisamos prestar muita atenção para o raciocínio envolvido.

So what are these principles of interpretation? Então, quais são esses princípios de interpretação? The first and by far the most prevalent such principle is a very straightforward one: it's a principle of verbal report. O primeiro e, de longe, o princípio mais prevalente como é muito simples: é um princípio de relato verbal. When someone says "Yes, I see that table now", we infer that they are conscious of the table. Quando alguém diz "Sim, eu vejo essa tabela agora", podemos inferir que eles estão conscientes da tabela. When someone says "Yes, I see red now", we infer that they are having an experience of red. Quando alguém diz "Sim, eu vejo vermelho agora", podemos inferir que eles estão tendo uma experiência de vermelho. Of course one might always say "How do you know?" É claro que sempre se pode dizer: "Como você sabe?" -- a philosopher might suggest that we may be faced with a fully functioning zombie - but in fact most of us don't believe that the people around us are zombies, and in practice we are quite prepared to rely on this principle. - Um filósofo poderia sugerir que nós podemos ser confrontados com um zumbi em pleno funcionamento - mas na verdade a maioria de nós não acreditamos que as pessoas ao nosso redor são zumbis, e, na prática estamos bem preparados para contar com este princípio. As pre-experimental assumptions go, this is a relatively "safe" one - it doesn't require a huge leap of faith - and it is very widely used.

Como pré-experimental suposições vão, este é relativamente um "seguro" - que não requer um enorme salto de fé - e é muito utilizado.

So the principle here is that when information is verbally reported, it is conscious. Assim, o princípio aqui é que quando a informação é relatada verbalmente, é consciente. One can extend this slightly, as no-one believes that an actual verbal report is required for consciousness; we are conscious of much more than we report on any given occasion. Pode-se estender esta ligeiramente, como ninguém acredita que um relatório real verbal é necessária para a consciência, estamos conscientes de muito mais do que informar sobre qualquer dada ocasião. So an extended principle might say that when information is directly available for verbal report, it is conscious. Assim, um princípio estendeu-se dizer que quando a informação está diretamente disponível para o relatório verbal, é consciente.

Experimental researchers don't rely only on these principles of verbal report and reportability. Pesquisadores experimentais não contar apenas com estes princípios do relatório verbal e reportability. These principles can be somewhat limiting when we want to do broader experiments. Estes princípios podem ser um pouco limitante quando queremos fazer experimentos mais amplo. In particular, we don't want to just restrict our studies of consciousness to subjects that have language. Em particular, nós não queremos apenas restringir nossos estudos de consciência para assuntos que têm a língua. In fact just this morning we saw a beautiful example of research on consciousness in language-free creatures. Na verdade esta manhã, vimos um belo exemplo de pesquisa sobre a consciência em linguagem livre de criaturas. I'm referring to the work of Nikos Logothetis and his colleagues (eg Logothetis & Schall 1989; Leopold & Logothetis 1996). Estou me referindo à obra de Nikos Logothetis e seus colegas (por exemplo, Logothetis & Schall, 1989; & Leopold Logothetis 1996). This work uses experiments on binocular rivalry in monkeys to draw conclusions about the neural processes associated with consciousness. Este trabalho utiliza experimentos sobre a rivalidade binocular em macacos para tirar conclusões sobre os processos neurais associadas com a consciência. How do Logothetis et al manage to draw conclusions about a monkey's consciousness without getting any verbal reports? Como Logothetis et al conseguem tirar conclusões sobre a consciência de um macaco sem obter relatos verbais? What they do is rely on a monkey's pressing bars: if a monkey can be made to press a bar in an appropriate way in response to a stimulus, we'll say that that stimulus was consciously perceived. O que eles fazem é confiar em barras de prensagem de um macaco: se um macaco pode ser feito para pressionar uma barra de forma apropriada em resposta a um estímulo, nós vamos dizer que esse estímulo foi percebido conscientemente.

The criterion at play seems to be require that the information be available for an arbitrary response. O critério em jogo parece ser necessário que a informação esteja disponível para uma resposta arbitrária. If it turned out that the monkey could press a bar in response to a red light but couldn't do anything else, we would be tempted to say that it wasn't a case of consciousness at all, but some sort of subconscious connection. Se descobriu-se que o macaco poderia pressionar uma barra em resposta a uma luz vermelha, mas não podia fazer mais nada, estaríamos tentados a dizer que não era um caso de consciência em tudo, mas algum tipo de conexão subconsciente. If on the other hand we find information that is available for response in all sorts of different ways, then we'll say that it is conscious. Se, por outro lado, encontramos a informação que está disponível para resposta em todos os tipos de maneiras diferentes, então vamos dizer que é consciente. Actually Logothetis and his colleagues also use some subtler reasoning about similarities with binocular rivalry in humans to buttress the claim that the monkey is having the relevant conscious experience, but it is clearly the response that carries the most weight. Na verdade Logothetis e seus colegas também usar alguns sutil raciocínio sobre semelhanças com a rivalidade binocular em seres humanos para apoiar a afirmação de que o macaco está tendo a experiência relevante consciente, mas é claramente a resposta que carrega o maior peso.

The underlying general principle is something like this: When information is directly available for global control in a cognitive system, then it is conscious. O princípio subjacente geral é algo como

isto: Quando a informação é diretamente disponível para o controle global de um sistema cognitivo, então é consciente. If information is available for response in many different motor modalities, we will say that it is conscious, at least in a range of relatively familiar systems such as humans and primates and so on. Se a informação está disponível para a resposta motora em diversas modalidades diferentes, vamos dizer que é consciente, pelo menos em uma gama de sistemas relativamente conhecidas, como seres humanos e primatas e assim por diante. This principle squares well with the previous principle in cases where the capacity for verbal report is present: availability for verbal report and availability for global control seem to go together in such cases (report is one of the key aspects of control, after all, and it is rare to find information that is reportable but not available more widely). Este princípio praças bem com o princípio anterior nos casos em que a capacidade de relato verbal é presente: a disponibilidade para o relatório verbal e disponibilidade para o controle global parecem ir juntos em tais casos (relatório é um dos aspectos-chave de controle, afinal, e é raro encontrar a informação que é, mas não reportáveis disponíveis de forma mais ampla). But this principle is also applicable more widely. Mas este princípio é também aplicável mais amplamente.

A correlation between consciousness and global availability (for short) seems to fit the first-person evidence - the evidence gleaned from our own conscious experience - quite well. A correlação entre consciência e disponibilidade global (para o short) parece ajustar-se a evidência em primeira pessoa - as provas colhidas pela nossa própria experiência consciente - muito bem. When information is present in my consciousness, it is generally reportable, and it can generally be brought to bear in the control of behavior in all sorts of different ways. Quando a informação está presente em minha consciência, é geralmente reportáveis, e geralmente pode ser exercida no controle de comportamento em todos os tipos de formas diferentes. I can talk about it, I can point in the general direction of a stimulus, I can press bars, and so on. Eu posso falar sobre isso, eu posso apontar na direção geral de um estímulo, eu posso pressionar barras, e assim por diante. Conversely, when we find information that is directly available in this way for report and other aspects of control, it is generally conscious information. Por outro lado, quando encontramos a informação que está diretamente disponível desta forma para o relatório e outros aspectos de controle, é a informação geralmente consciente. I think one can bear this out by consideration of cases. Acho que se pode comprovar isso por conta dos casos.

There are some interesting puzzle cases to consider, such as the case of blindsight, where one has some kind of availability for control but arguably no conscious experience. Existem alguns casos de quebra-cabeça interessante considerar, como o caso da cegueira, onde se tem algum tipo de disponibilidade para o controle, mas sem dúvida nenhuma experiência consciente. Those cases might best be handled by invoking the directness criterion: insofar as the information here is available for report and other control processes at all, it is available only indirectly, by comparison to the direct and automatic availability in standard cases. Nesses casos pode ser melhor tratado por invocando o critério de objetividade: na medida em que as informações aqui está disponível para relatórios e outros processos de controle em tudo, ele está disponível apenas indiretamente, por comparação com a disponibilidade directa e automática em casos normais. One might also stipulate that it is availability for voluntary control that is relevant, to deal with certain cases of involuntary unconscious response, although that is a complex issue. Pode-se também prever a sua disponibilidade para o controle voluntário que é relevante, para lidar com certos casos de resposta inconsciente involuntário, apesar de que é uma questão complexa. I discuss a number of puzzle cases in more detail elsewhere (Chalmers 1996, forthcoming), where I also give a much more detailed defence of the idea that something like global availability is the key pre-empirical criterion for the ascription of consciousness. I discutir um número de casos de quebra-cabeça com mais detalhes em outro lugar (Chalmers 1996, no prelo), onde também dou uma defesa muito mais detalhada da idéia de que algo como a disponibilidade global é o critério pré-empírico-chave para a atribuição de consciência.

But this remains at best a first-order approximation of the functional criteria that come into play.

Mas este continua sendo o melhor em uma aproximação de primeira ordem dos critérios funcionais que entram em jogo. I'm less concerned today to get all the fine details right than to work with the idea that some such functional criterion is required and indeed is implicit in all the empirical research on the neural correlate of consciousness. Estou menos preocupado hoje para obter todos os detalhes certos do que para trabalhar com a idéia de que algum critério como funcional é necessária e, na verdade está implícita em todas as pesquisas empíricas sobre o correlato neural da consciência. If you disagree with the criterion I've suggested here - presumably because you can think of counterexamples - you may want to use those counterexamples to refine it or to come up with a better criterion of your own. Se você não concordar com o critério que eu sugeri aqui - provavelmente porque você pode pensar de contra-exemplos - você pode querer usar os contra-exemplos para refiná-la ou para chegar a um melhor critério de seu próprio país. But the point I want to focus on here is that in the very act of experimentally distinguishing conscious from unconscious processes, some such criterion is always at play. Mas o ponto que quero focar aqui é que no próprio ato de distinguir experimentalmente conscientes dos processos inconscientes, alguns desses critérios é sempre em jogo.

So the question I want to ask is: if something like this is right, then what follows? Então, a pergunta que eu quero perguntar é: se algo como isto está certo, então o que se segue? That is, if some such bridging principles are implicit in the methodology of the search for the NCC, then what are the consequences? Ou seja, se alguns princípios, tais ponte estão implícitas na metodologia da pesquisa para o NCC, em seguida, quais são as consequências? I will use global availability as my central functional criterion in the discussion that follows, but many of the points should generalize. Vou usar a minha disponibilidade global como critério central funcional na discussão que se segue, mas muitos dos pontos deve generalizar.

The first thing one can do is produce what philosophers might call a rational reconstruction of the search for the neural correlate of consciousness. A primeira coisa que se pode fazer é produzir o que os filósofos poderiam chamar de uma reconstrução racional da pesquisa para o correlato neural da consciência. With a rational reconstruction we can say, maybe things don't work exactly like this in practice, but the rational underpinnings of the process have something like this form. Com uma reconstrução racional, podemos dizer, talvez as coisas não funcionam exatamente assim na prática, mas os fundamentos racionais do processo de ter algo parecido com este formulário. That is, if one were to try to justify the conclusions one has reached as well as one can, one's justification would follow the shape of the rational reconstruction. Ou seja, se alguém tentar justificar as conclusões alguem atingiu, assim como pode-se, é uma justificação iria seguir a forma da reconstrução racional. In this case, a rational reconstruction might look something like this: Neste caso, uma reconstrução racional poderia ser algo como isto:

(1) Consciousness <-> global availability (bridging principle) (1) Consciência <-> disponibilidade global (bridging princípio)

(2) Global availability <-> neural process N (empirical work) (2) a disponibilidade global <-> processo neural N (trabalho empírico)

so assim

(3) Consciousness <-> neural process N (conclusion). (3) Consciência <-> processo neural N (conclusão).

According to this reconstruction, one implicitly embraces some sort of pre-experimental bridging principle that one finds plausible on independent grounds, such as conceptual or phenomenological grounds. De acordo com esta reconstrução, um abraça implicitamente algum tipo de pré-experimental princípio ponte que se encontra plausível por motivos independentes, como fundamentos conceituais ou fenomenológica. Then one does the empirical research. Então se faz a pesquisa empírica. Instead of measuring consciousness directly, we detect the functional property. Em vez de medir a consciência diretamente, nós detectamos a propriedade funcional. One sees that

when this functional property (eg global availability) is present, it is correlated with a certain neural process (eg 40-hertz oscillations). Vê-se que quando esta propriedade funcional (disponibilidade global, por exemplo) está presente, é correlacionada com um determinado processo neural (por exemplo, de 40 hertz oscilações). Combining the pre-empirical premise and the empirical result, we arrive at the conclusion that this neural process is a candidate for the NCC. Combinando a premissa pré-empíricos e os resultados empíricos, chegamos à conclusão de que este processo neural é um candidato para o NCC.

Of course it doesn't work nearly so simply in practice. Claro que não funciona quase tão simples na prática. The two stages are very intertwined; our pre-experimental principles may themselves be refined as experimental research goes along. As duas fases são muito interligadas, a nossa pré-experimental princípios pode-se ser refinado como a pesquisa experimental vai junto. Nevertheless I think one can make a separation, at least at the rational level, into pre-empirical and experimental components, for the sake of analysis. No entanto creio que se possa fazer uma separação, pelo menos no nível racional, em componentes pré-empírica e experimental, para fins de análise. So with this sort of rational reconstruction in hand, what sort of conclusions follow? Assim, com este tipo de reconstrução racional na mão, que tipo de conclusões seguir? There are about six consequences that I want to draw out here. Há cerca de seis conseqüências que quero chamar aqui.

(1) The first conclusion is a characterization of the neural correlates of consciousness. (1) A primeira conclusão é a caracterização dos correlatos neurais da consciência. If the NCC is arrived at through this sort of methodology, then whatever it turns out to be, it will be a mechanism of global availability . Se o NCC é que se chegou através deste tipo de metodologia, em seguida, seja lá o que acaba por ser, será um mecanismo de disponibilidade global. The presence of the NCC wherever global availability is present suggests that it is a mechanism that subserves the process of global availability in the brain. A presença da disponibilidade mundial onde NCC está presente sugere que é um mecanismo que subserves o processo de disponibilidade global do cérebro. The only alternative that we have to worry about is that it might be a symptom rather than a mechanism of global availability; but that possibility ought to be addressable in principle by dissociation studies, by lesioning, and so on. A única alternativa que temos que se preocupar é que ele pode ser um sintoma e não um mecanismo de disponibilidade global, mas essa possibilidade deve ser endereçável, em princípio, pela dissociação estudos, por a lesão, e assim por diante. If a process is a mere symptom of availability, we ought to be able to empirically dissociate it from the process of global availability while leaving the latter intact. Se um processo é um mero sintoma de disponibilidade, devemos ser capazes de dissociá-la empiricamente a partir do processo de disponibilidade global, deixando o último intacta. The resulting data would suggest to us that consciousness can be present even when the neural process in question is not, thus indicating that it wasn't a perfect correlate of consciousness after all. Os dados resultantes sugeriria para nós que a consciência pode estar presente mesmo quando o processo neural em questão não é, indicando que não era uma perfeita correlação de consciência depois de tudo.

(A related line of reasoning supports the idea that a true NCC must be a mechanism of direct availability for global control. Mechanisms of indirect availability will in principle be dissociable from the empirical evidence for consciousness, for example by directly stimulating the mechanisms of direct availabilty. The indirect mechanisms will be "screened off" by the direct mechanisms in much the same way as the retina is screened off as an NCC by the visual cortex.) (A linha de raciocínio relacionados suporta a idéia de que um NCC verdadeira deve ser um mecanismo de disponibilidade direta para o controle global. Mecanismos de disponibilidade indiretos serão em princípio indissociável da evidência empírica para a consciência, por exemplo, estimulando diretamente os mecanismos de availabilty direta . Os mecanismos indiretos serão "encoberta" por mecanismos diretos em muito da mesma forma que a retina é encoberta como um NCC pelo córtex visual.)

In fact, if one looks at the various proposals that are out there, this template seems to fit them pretty well. Na verdade, se olharmos para as várias propostas que estão lá fora, este modelo parece se encaixar-los muito bem. For example, the 40-hertz oscillations discussed by Crick and Koch were put forward precisely because of the role they might play in binding and integrating information into working memory, and working memory is of course a central mechanism whereby information is made available for global control in a cognitive system. Por exemplo, as oscilações de 40 hertz discutido por Crick e Koch foram apresentadas precisamente por causa do papel que pode desempenhar na ligação e integração de informações na memória de trabalho e memória de trabalho é, naturalmente, um mecanismo central pelo qual a informação é disponibilizada para o controle global em um sistema cognitivo. Similarly, it is plausible that Libet's extended neural activity is relevant precisely because the temporal extendedness of activity is what gives certain information the capacity to dominate later processes that lead to control. Da mesma forma, é plausível que a atividade neural estendida de Libet é relevante justamente porque a extendedness temporal da atividade é o que dá algumas informações a capacidade de dominar os processos depois que levam ao controle. Baars' global workspace is a particularly explicit proposal of a mechanism in this direction; it is put forward explicitly as a mechanism whereby information can be globally disseminated. Espaço de trabalho global Baars "é uma proposta particularmente explícito de um mecanismo nessa direção, é apresentada explicitamente como um mecanismo pelo qual a informação pode ser disseminada globalmente. All of these mechanisms and many of the others seem to be candidates for mechanisms of global availability in the brain. Todos esses mecanismos e muitos dos outros parecem ser candidatos para os mecanismos de disponibilidade global do cérebro.

(2) This reconstruction suggests that a full story about the neural processes associated with consciousness will to do two things. (2) Esta reconstrução sugere que uma história completa sobre os processos neurais associadas com a consciência vai fazer duas coisas. Firstly, it will explain global availability in the brain. Em primeiro lugar, ele irá explicar a disponibilidade global do cérebro. Once we know all about the relevant neural processes, we will know precisely how information is made directly available for global control in the brain, and this will be an explanation in the full sense. Uma vez que sabemos tudo sobre os processos relevantes neural, saberemos exatamente como a informação é feita diretamente disponíveis para o controle global no cérebro, e isso vai ser uma explicação, no sentido pleno. Global availability is a functional property, and as always the problem of explaining the performance of a function is a problem to which mechanistic explanation is well-suited. Disponibilidade global é uma propriedade funcional, e como sempre o problema de explicar o desempenho de uma função é um problema para o qual a explicação mecanicista é bem adequada. So we can be confident that in a century or two global availability will be straightforwardly explained. Assim, podemos estar confiantes de que em um século ou dois disponibilidade global será diretamente explicado. Secondly, this explanation of availability will do something else: it will isolate the processes that underlie consciousness itself. Em segundo lugar, esta explicação de disponibilidade vai fazer outra coisa: ele vai isolar os processos que subjazem a própria consciência. If the bridging principle is granted, then mechanisms of availability will automatically be correlates of phenomenology in the full sense. Se o princípio de ligação é concedido, então mecanismos de disponibilidade será automaticamente correlatos da fenomenologia no sentido pleno.

Now, I don't think this gives us a full explanation of consciousness. Agora, eu não acho que isso nos dá uma explicação completa de consciência. One can always raise the question of why it is that these processes of availability should give rise to consciousness in the first place. Sempre se pode levantar a questão de porque é que estes processos de disponibilidade deve dar origem à consciência, em primeiro lugar. As yet we have no explanation of why this is, and it may well be that the full details concerning the processes of availability still won't answer this question. Como ainda não temos explicação de por que isso é, e pode muito bem ser que a todas as informações sobre os processos de disponibilidade ainda não vai responder a esta pergunta. Certainly, nothing in

the standard methodology I have outlined answers the question; that methodology assumes a relation between availability and consciousness, and therefore does nothing to explain it. Certamente, nada na metodologia padrão, expus responde à pergunta, que metodologia pressupõe uma relação entre disponibilidade e consciência, e, portanto, não faz nada para explicar. The relationship between the two is instead taken as something of a primitive. A relação entre os dois é tida como algo, em vez de um primitivo. So the hard problem still remains. Então, o problema continua a ser difícil. But who knows: somewhere along the line we may be led to the relevant insights that show why the link is there, and the hard problem may then be solved. Mas quem sabe: em algum lugar ao longo da linha que pode ser levado à insights relevantes que mostram por que o link está lá, e o problema difícil pode ser resolvido. In any case, whether or not we have solved the hard problem, we may nevertheless have isolated the basis of consciousness in the brain. Em qualquer caso, se temos ou não resolveu o problema difícil, podemos, no entanto, ter isolado a base da consciência no cérebro. We just have to keep in mind the distinction between correlation and explanation. Nós apenas temos que manter em mente a distinção entre correlação e explicação.

(3) Given this paradigm, it is likely that there are going to be many different neural correlates of consciousness. (3) Diante desse paradigma, é provável que não vão ser muitos diferentes correlatos neurais da consciência. I take it that this is not going to surprise many people; but the rational reconstruction gives us a way of seeing just why such a multiplicity of correlates should exist. Eu entendo que isso não vai surpreender muitas pessoas, mas a reconstrução racional nos dá uma maneira de ver apenas por uma multiplicidade de tais correlações deveria existir. There will be many neural correlates of consciousness because there may well be many different mechanisms of global availability. Haverá muitos correlatos neurais da consciência, porque pode haver muitos mecanismos diferentes de disponibilidade global. There will be mechanisms of availability in different modalities: the mechanisms of visual availability may be quite different from the mechanisms of auditory availability, for example. Haverá mecanismos de disponibilidade em diferentes modalidades: os mecanismos de disponibilidade visual pode ser bastante diferente dos mecanismos de disponibilidade auditivo, por exemplo. (Of course they may be the same, in that we could find a later area that integrates and disseminates all this information, but that's an open question.) There will also be mechanisms at different stages of the processing path whereby information is made globally available: early mechanisms and later ones. (É claro que eles podem ser os mesmos, em que nós poderíamos encontrar uma área mais tarde que integra e divulga todas essas informações, mas isso é uma questão em aberto.) Haverá também mecanismos em diferentes estágios do caminho de processamento pelo qual a informação é feita globalmente disponíveis : mecanismos cedo e os posteriores. So these may all be candidates for the NCC. Assim, estes podem ser todos candidatos para o NCC. And there will be mechanisms at many different levels of description: for example, 40-hertz oscillations may well be redescribed as high-quality representations, or as part of a global workspace, at a different level of description. E haverá mecanismos em muitos níveis diferentes de referência: por exemplo, de 40 hertz oscilações podem muito bem ser redescrita como de alta qualidade representações, ou como parte de um espaço de trabalho global, em um nível diferente da descrição. So it may turn out that a number of the animals in the zoo, so to speak, can co-exist, because they are compatible in one of these ways. Assim, pode acontecer que um número de animais no zoológico, por assim dizer, pode co-existir, porque eles são compatíveis em uma dessas maneiras.

I won't speculate much further on just what the neural correlates of consciousness are . Eu não vou especular muito sobre o que os correlatos neurais da consciência são. No doubt some of the ideas in the initial list will prove to be entirely off-track, while some of the others will prove closer to the mark. Sem dúvida, algumas das idéias na lista inicial irá revelar-se inteiramente fora de pista, enquanto alguns dos outros irá provar mais perto da marca. As we philosophers like to say, humbly, that's an empirical question. À medida que os filósofos gostam de dizer, humildemente, que é uma questão empírica. But I hope the conceptual issues are becoming clearer. Mas eu espero que as

questões conceituais estão se tornando mais clara.

(4) This way of thinking about things allows one to make sense of a idea that is sometimes floated: that of a consciousness module . (4) Esta forma de pensar sobre as coisas permite dar sentido a uma ideia de que às vezes é lançada: a de um módulo de consciência. Sometimes this notion is disparaged; sometimes it is embraced. Às vezes, essa noção é menosprezado, por vezes, é abraçado. But this picture of the methodology in the search for an NCC suggests that it is at least possible that there could turn out to be such a module. Mas esta imagem da metodologia na busca de um NCC sugere que é pelo menos possível que não poderia revelar-se como um módulo. What would it take? O que seria necessário? It would require that there turns out to be some sort of functionally localizable, internally integrated area, through which all global availability runs. Seria necessário que acaba por ser uma espécie de localizável funcionalmente, área interna integrada, através do qual toda a disponibilidade mundial é executado. It needn't be anatomically localizable, but to qualify as a module it would need to be localizable in some broader sense. Não precisa ser anatomicamente localizáveis, mas para se qualificar como um módulo que teriam de ser localizável em algumas sentido mais amplo. For example, the parts of the module would have to have high-bandwidth communication among themselves, compared to the relatively low-bandwidth communication that they have with other areas. Por exemplo, as partes do módulo teria que ter alta largura de banda de comunicação entre si, em comparação com o relativamente baixa largura de banda de comunicação que têm com outras áreas. Such a thing could turn out to exist. Tal coisa pudesse vir a existir. It doesn't strike me as especially likely that things will turn out this way; it seems just as likely that there will be multiple independent mechanisms of global availability in the brain, scattered around without any special degree of mutual integration. Não me parece especialmente provável que as coisas vão sair desta forma, parece bem provável que haverá vários mecanismos independentes de disponibilidade global no cérebro, espalhadas sem nenhum grau especial de integração mútua. If that's so, we will likely say that there doesn't turn out to be a consciousness module after all. Se é assim, é bem provável que dizer que lá não vir a ser um módulo de consciência depois de tudo. But that's another one of those empirical questions. Mas isso é outra daquelas questões empíricas.

If something like this does turn out to exist in the brain, it would resemble Baars' conception of a global workspace: a functional area responsible for the integration of information in the brain and for its dissemination to multiple nonconscious specialized processes. Se algo como isso não vir a existir no cérebro, ele seria semelhante concepção Baars "de um espaço de trabalho global: uma área funcional responsável pela integração de informações no cérebro e para a sua divulgação a vários processos inconscientes especializados. In fact I should acknowledge that many of the ideas I'm putting forward here are compatible with things that Baars has been saying for years about the role of global availability in the study of consciousness. Na verdade eu deveria reconhecer que muitas das idéias que eu estou propondo aqui são compatíveis com as coisas que Baars vem dizendo há anos sobre o papel da disponibilidade mundial no estudo da consciência. Indeed, this way of looking at things suggests that some of his ideas are almost forced on one by the methodology. Na verdade, esta maneira de olhar as coisas sugere que algumas de suas idéias são quase forçado em um pela metodologia. The special epistemological role of global availability helps explain why the idea of a global workspace provides a useful way of thinking about almost any empirical proposal about consciousness. O papel especial epistemológico da disponibilidade mundial ajuda a explicar porque a idéia de um espaço de trabalho global fornece uma maneira útil de pensar sobre quase qualquer proposta empíricas sobre a consciência. If NCC's are identified as such precisely because of their role in global control, then at least on a first approximation, we should expect the global workspace idea to be a natural fit. Se NCC são identificadas como tal, precisamente devido ao seu papel no controle global, pelo menos em uma primeira aproximação, devemos esperar que a idéia do espaço de trabalho global para ser um ajuste natural.

(5) We can also apply this picture to a question that has been discussed frequently at this conference: are the neural correlates of visual consciousness to be found in V1, in the extrastriate visual cortex, or elsewhere? (5) Podemos também aplicar essa imagem para uma questão que tem sido discutido com freqüência nesta conferência: são os correlatos neurais da consciência visual para ser encontrado em V1, no córtex visual extra-estriado, ou em outro lugar? If our picture of the methodology is correct, then the answer will presumably depend on which visual area is most directly implicated in global availability. Se a nossa imagem da metodologia é correta, então a resposta vai depender de qual presumivelmente área visual é mais diretamente implicados na disponibilidade global.

Crick and Koch have suggested that the visual NCC is not to be found within V1, as V1 does not contain neurons that project to the prefrontal cortex. Crick e Koch sugerem que o NCC visual não deve ser encontrada dentro de V1, como V1 não contém neurônios que se projetam para o córtex pré-frontal. This reasoning has been criticized by Ned Block for conflating access consciousness and phenomenal consciousness (see Block, this volume); but interestingly, the picture I have developed suggests that it may be good reasoning. Este raciocínio tem sido criticado por Ned Block para confundir a consciência de acesso e da consciência fenomenal (ver Block, neste volume), mas curiosamente, a imagem que tenho desenvolvido sugere que pode ser bom raciocínio. The prefrontal cortex is known to be associated with control processes; so if a given area in the visual cortex projects to prefrontal areas, then it may well be a mechanism of direct availability. O córtex pré-frontal é conhecido por estar associado a processos de controlo; por isso, se uma determinada área nos projetos córtex visual para áreas pré-frontais, então ele pode muito bem ser um mecanismo de disponibilidade direta. And if it does not project in this way, it is less likely to be such a mechanism; at best it might be indirectly associated with global availability. E se não projeto, desta forma, é menos provável de ser um mecanismo desse tipo, na melhor das hipóteses, pode ser indiretamente associados à disponibilidade global. Of course there is still plenty of room to raise questions about the empirical details. Claro que há ainda muito espaço para levantar questões sobre os detalhes empíricos. But the broader point is that for the sort of reasons discussed in (2) above, it is likely that the neural processes involved in explaining access consciousness will simultaneously be involved in a story about the basis of phenomenal consciousness. Mas o ponto principal é que para o tipo de razões discutidas em (2) acima, é provável que os processos neurais envolvidos na explicação da consciência de acesso será, simultaneamente, estar envolvido em uma história sobre a base da consciência fenomenal. If something like this is implicit in their reasoning, Crick and Koch might escape the charge of conflation. Se algo como isso está implícito no seu raciocínio, Crick e Koch poderia escapar da acusação de fusão. Of course the reasoning does depend on these somewhat shaky bridging principles, but then all work on the neural correlates of consciousness must appeal to such principles somewhere, so this can't be held against Crick and Koch in particular. É claro que o raciocínio não depende de estes princípios um pouco instável ponte, mas depois todo o trabalho sobre os correlatos neurais da consciência deve apelar a tais princípios em algum lugar, então isso não pode ser usado contra Crick e Koch, em particular.

(6) Sometimes the neural correlate of consciousness is conceived of as the Holy Grail for a theory of consciousness. (6) Às vezes, o correlato neural da consciência é concebida como o Santo Graal para uma teoria da consciência. It will make everything fall into place. Ele vai fazer cair tudo no lugar. For example, once we discover the NCC, then we'll have a definitive test for consciousness, enabling us to discover consciousness wherever it arises. Por exemplo, quando descobrimos o NCC, então nós vamos ter um teste definitivo para a consciência, que nos permite descobrir a consciência sempre que surge. That is, we might use the neural correlate itself as a sort of consciousness meter. Ou seja, podemos usar o correlato neural-se como uma espécie de medidor de consciência. If a system has 40-hertz oscillations (say), then it is conscious; if it has none, then it is not conscious. Se um sistema tem de 40 hertz oscilações (digamos), então ele está consciente, se ele não tem nenhuma, então não é consciente. Or if a thalamocortical system turns out to be the NCC, then a

system without that system is unlikely to be conscious. Ou se um sistema tálamo-cortical acaba por ser o NCC, em seguida, um sistema sem que o sistema é improvável que seja consciente. This sort of reasoning is not usually put quite so baldly as this, but I think one finds some version of it quite frequently. Este tipo de raciocínio não é normalmente colocado tão descaradamente como este, mas acho que se encontra alguma versão dela com bastante freqüência.

This reasoning can be tempting, but one should not succumb to the temptation. Esse raciocínio pode ser tentador, mas não se deve sucumbir à tentação. Given the very methodology which comes into play here, there is no way to definitely establish a given NCC as an independent test for consciousness. Dada a metodologia muito que entra em jogo aqui, não há maneira de estabelecer definitivamente um NCC dado como um teste independente para a consciência. The primary criterion for consciousness will always remain the functional property we started with: global availability, or verbal report, or whatever. O principal critério para a consciência será sempre a propriedade funcional começamos com: disponibilidade global, ou um relatório verbal, ou o que quer. That's how we discovered the correlations in the first place. É assim que descobriu as correlações, em primeiro lugar. 40-hertz oscillations (or whatever) are relevant only because of the role they play in satisfying this criterion. 40 hertz oscilações (ou qualquer outro) são relevantes só por causa do papel que desempenham em satisfazer este critério. True, in cases where we know that this association between the NCC and the functional property is present, the NCC might itself function as a sort of "signature" of consciousness; but once we dissociate the NCC from the functional property, all bets are off. Verdadeiro, nos casos em que sabemos que essa associação entre o NCC ea propriedade funcional está presente, a NCC pode-se funcionar como uma espécie de "assinatura" de consciência, mas uma vez que dissociar o NCC a partir da propriedade funcional, todas as apostas estão fora . To take an extreme example, if we have 40-hertz oscillations in a test tube, that almost certainly won't yield consciousness. Para tomar um exemplo extremo, se tivermos 40 hertz oscilações em um tubo de ensaio, que quase certamente não renderá consciência. But the point applies equally in less extreme cases. Mas o ponto aplica-se igualmente em casos menos extremos. Because it was the bridging principles that gave us all the traction in the search for an NCC in the first place, it's not clear that anything follows in cases where the functional criterion is thrown it away. Porque foi a princípios de extrapolação que nos deu toda a tracção de na busca de um NCC, em primeiro lugar, não é claro que nada segue nos casos em que o critério funcional é jogado fora. So there's no free lunch here: one can't get something for nothing. Portanto, não há almoço de graça aqui: não se pode obter algo para nada.

Once one recognizes the central role that pre-experimental assumptions play in the search for the NCC, one realizes that there are some limitations on just what we can expect this search to tell us. Uma vez que se reconhece o papel central que a pré-experimental suposições jogar em busca do NCC, percebe-se que existem algumas limitações sobre o que podemos esperar desta pesquisa para nos dizer. Still, whether or not the NCC is the Holy Grail, I hope that I have said enough to make it clear that the quest for it is likely to enhance our understanding considerably. Ainda assim, se o NCC é o Santo Graal, espero que eu tenha dito o suficiente para deixar claro que a busca por ela é susceptível de reforçar a nossa compreensão consideravelmente. And I hope to have convinced you that there are important ways in which philosophy and neuroscience can come together to help clarify some of the deep problems involved in the study of consciousness. E espero tê-lo convencido de que há aspectos importantes em que a filosofia e neurociência podem se unir para ajudar a esclarecer alguns dos profundos problemas envolvidos no estudo da consciência.

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