Understanding the Neuroself: Patricia Smith Churchland's Perspective, Lecture notes of Philosophy

Download Understanding the Neuroself: Patricia Smith Churchland's Perspective and more Lecture notes Philosophy in PDF only on Docsity! [ 41 ] PROCEEDINGS OF THE AMERICAN PHILOSOPHICAL SOCIETY VOL. 155, NO. 1, MARCH 2011 1 Read 24 April 2009, as part of the symposium “The Relation of Organ, Limb, and Face Transplantation.” This article is based on chapter 3, “Self & Self-Knowledge,” in Brain-Wise (Cambridge, Mass.: MIT Press, 2002). The Brain and Its Self 1 PATRICIA SMITH CHURCHLAND Philosophy Department University of California, San Diego NAKING OUT of the MRI tube where I had lain for the past half hour, I glimpsed Dr. Hanna Damasio studying the lab’s dis- play screen. Off the gurney, I went to her side and stared at the S image of my brain on the screen. “Is that—me?” Well, yes, in a certain sense. And yet not simply, or merely, me. Certainly not familiarly me. Here is what I thought: “Somehow, starting in infancy, my brain built a story about itself—its body, its history, its ‘now,’ and its world. From the inside, I know that story—though I think of it as reality, not just a story. Indeed, it is my inner reality. So how does this happen? What is it for me to be a construction of my brain?” In one form or another, these questions have had a long and convo- luted history, born in the unfl inching curiosity of the ancient Greeks, and fi nding voice in diverse cultures. Until recently, the only explana- tory resources for addressing puzzling behavior depended on mytholo- gizing in the case of others, and myth-fi ltered introspection in the case of oneself. Not surprisingly, early explanations invoked possession by devils or, if you were luckier, divine forces, to account for epileptic sei- zures or schizophrenic hallucinations. In the absence of understanding, the punishment theory of mental dysfunction commanded widespread belief, yet it was wholly untestable—and essentially untested. Melancholia (what we now call chronic depression) and phobias were often surmised to be essentially character fl aws—fl aws that might be overcome with suffi cient gumption. The existence of witches, hexes, curses, and spells had a far longer history as brute fact than does our appreciation of such potent neurochemicals as serotonin. Obsessive hand- washing, a mere fi fteen years ago, was widely assumed to be a manifes- tation of repressed sexuality. Nevertheless, even as early as 400 BC, the great Greek physician, Hippocrates, was convinced that events such as 42 patricia smith churchland sudden paralysis or creeping dementia had their originating causes in brain damage—which implied, in his view, that normal movement and normal speech had their originating causes in the well-tempered brain. Brains, however, are not easy organs to fi gure out. Imagine Hip- pocrates, dissecting the brain of a dead warrior after autopsy, and pon- dering an area of sword-destroyed tissue. To what theoretical resources could he reach to begin to make sense of something so complex as the relation between fl uent speech and the pinkish tissue found in the skull? Remember, in 400 BC nothing was understood about the nature of the cells that make up the body, let alone of the special nature of the cells that make up the brain. Techniques for isolating neurons—brain cells— to see what they looked like could begin only in the nineteenth century. Techniques for isolating living neurons to explore their function did not appear until well into the twentieth century. Figuring out how neurons do what they do requires high-level tech- nology. And that, needless to say, depends on immense infrastructural science; on cell biology, advanced physics, and twentieth-century chem- istry. It requires sophisticated modern notions like molecule and protein, and modern tools like the light microscope and the electron microscope. What is most important, making progress on how brains work de- pended on understanding electricity. This is because what makes brain cells special is their capacity to signal one another by causing fast micro changes in each other’s electrical state. Living as we do in an electrical world, it is sobering to recall that as late as 1800, electricity was typi- cally considered deeply mysterious and quite possibly occult. Only a fter discoveries by Ampère and Faraday at the dawn of the nineteenth century was electricity clearly understood to be a physical phenome- non, behaving according to well-defi ned laws, and capable of being harnessed for practical purposes. In this century, modern neuroscience and psychology allow us to go beyond myth and introspection to approach the “self” as a natural phe- nomenon whose causes and effects can be addressed by science. Helped by new experimental techniques and new explanatory tools, we can pry loose real understanding of how the brain comes to know its own body, how it builds a coherent model of its world, and how changes in brain tissue can entail changes in the very self itself. Neurobiology is beginning to reveal why some brains are more susceptible than others to alcohol or heroin addiction, or why some brains slide into incoher- ent world-models. Progress is visible on the staged emergence of self in childhood, as well as the cruel inch-by-inch loss of self in dementia. Though well short of full answers, neuroscience has discovered much about the effects of localized brain lesions on complex decision making or speech or voluntary behavior. the brain and its self 45 3. Brains Emulate Body and Self A. The General Idea Referring to “the self” suggests the self must be a kind of thing, such as a specifi c organ in the brain, the way that the spleen or the pancreas is a specifi c organ in the body. Clearly, however, the “pancreas paradigm” for thinking about the self won’t work. The self is not an organ in the brain; nor, so far as we know, is there a discrete region of the brain that “makes” the self. But if the self is not a thing like the pancreas, and if it is not a continuous sensation, what is it? The best hypothesis is that it involves a complex idea (representa- tion) that the brain generates through activity in various different re- gions, including the regions representing the body and a representation using memory of the past. The brain activity that we know introspec- tively as “myself” is probably part of a set of larger patterns of activity the brain deploys for making sense of and getting by in its world. Given these considerations, it is preferable to talk about the problem of self- representation rather than the problem of the self. But what is it for the brain to represent anything, let alone “self”? Must there not be a self if the brain represents it? B. Representation in the Brain Part of the major business of nervous systems, from crayfi sh to humans, is to make good predictions about food, mates, enemies, and friends, so that the body can live on to reproduce. Poor predictors often end up as meals for better predictors. Imposing structure on our sensory stimuli in the service of better prediction is what representation is all about. Using internal representations allows for much more sophisticated be- havior than mere stimulus-response refl exes. Using internal representa- tions is a common strategy that nervous systems have developed as part of evolution’s way of favoring adaptive structures. The philosopher Rick Grush2 has developed a useful tool for get- ting a handle on this. Suppose I am running a huge construction crane, which is a very high-tech crane that I can operate from the comfort of my offi ce a mile away. It would be a good idea for the engineer to de- sign it so that I have access to a small-scale model that shows where the hook will be if I give the order for a certain movement. That way I can correct my movement without waiting for feedback from the gigantic 2 See Rick Grush, “Emulation and Cognition” (Ph.D. diss., UCSD, 1995); idem, “The A rchitecture of Representation,” Philosophical Psychology 10 (1997): 5–25. 46 patricia smith churchland hook-in-the-world. The emulator in my offi ce generates internal feed- back that helps me predict. Even better, the designer could allow me to fi ddle with the model so that I can test possible movements before I choose the best, thereby maximizing the accuracy of the movement when I do fi nally make the actual hook move. Very crudely, this is what Grush thinks brains do. They build “emulators” of the world and of their bodies in that world. Of course if you looked in my brain you would not see a minia- ture world of tiny trees and dogs and so forth—just cells connected to cells, signaling each other and displaying patterns of activity. Nor is there a little person in my head who sits and watches a screen. That part of the emulator story does not at all fi t what brains do. What we can take from the emulator story is the similarity in function. Some patterns of neuronal activity seem to be performing the same function as the crane-emulator. Exactly how this works is not known. Nevertheless, it seems evident that inner modeling of the body and its world is an evolutionary achieve- ment that means the organism can do smarter things than other wise. Not all aspects of the organism’s world need be emulated in its brain— only those that matter to it, given its way of making a living.3 Bees can de- tect ultraviolet light, and that helps them forage among fl owers. Humans do not perceptually represent that aspect of the world, unless we build a tool to do it for us. In a similar vein, I shall not need all aspects of the crane-world explicitly emulated—just those relevant to getting the job done. Some world-emulation will be on- line, as when the brain displays per- ceptual construction and fi lling-in. Thus we see a Dalmatian in the leafy background even though the stimulus itself is degraded (fi g. 1). We see the tomato as uniformly red even though it is shadowed and highlighted and partially occluded; we hear our names spoken in a noisy room. Off-line, so to speak, we remember where we cached the food by the river; we plan how to cross a turbulent stream; we daydream and fantasize. Figure 1. A Dalmatian dog in the dappled light, standing on a leaf-strewn pavement 3 Kathleen Akins, “Of Sensory Systems and the ‘Aboutness’ of Mental States,” Journal of Philosophy 93.7 (1996): 337–72. the brain and its self 47 On the Grush hypothesis, the brain emulates the ecologically relevant —the “relevant-to-my-kind-of-creature”—features of the world, and then m anipulates these emulations to plan, hide, forage, and so forth. I may consider the problem of crossing the turbulent stream, go on to imagine a route that would be easier if a log were stretched from one rock to another, and go on to imagine the size of the log needed and how to get it into place. This involves manipulation of the image or, as we may say, of the river-crossing emulation. C. Body Models So far we have focused on emulations that capture features of the out- side world, but brains can also emulate aspects of the body. You can, for example, imagine your body standing when you are sitting, or the size it was when you were fi ve. Sexual fantasies are potent instances in which real body effects can be produced by the brain’s manipulation of a two-body emulation. Imaginary tennis and golf have been demon- strated to be highly signifi cant in improving one’s actual game. Hiding your body from another viewer requires enormous represen- tational sophistication. You need some understanding of the visual as- pect of your body, its proportions relative to the shield. Most critically, you need to grasp how the scene will look from another’s viewpoint. Remember playing hide-and-seek, and the importance of knowing the visibility of one’s body from various perspectives. From the perspective of whoever is “it,” there must be no feet sticking out, no hair showing above, though visibility to our fellow hiders doesn’t matter. A very young child may think she is hidden from others when she puts her hands over her eyes. She does not yet have a representation of how she looks from another’s eyes. But she probably has spent lots of time watching her fi ngers manipulate food, toys, the dog, and her own toes, and probably her visually-anchored body-schema is still emerging. An integrated body-schema, with both visual and somatosensory di- mensions, will have begun to develop from her very early days, even if she cannot yet manage all the subtleties of the difference between “I can see me” and “You can see me.” D. Self-Models Additionally, complex brains can emulate aspects of what the brain itself is doing, and the “self,” I suggest, is one such result. That is, it may have a model of the brain’s activities, perhaps cast in perceptual images resem- bling familiar external events. As the philosopher Patricia Kitcher sees it, something like this is what Kant had in mind as the basis for “self.”