The Single-Neuron Theory: Closing in on the Neural Correlate of Consciousness PDF
Preview The Single-Neuron Theory: Closing in on the Neural Correlate of Consciousness
steven sevush the single-neuron theory closing in on the neural correlate of consciousness The Single-Neuron Theory Steven S evush The Single-Neuron Theory Closing in on the Neural Correlate of Consciousness Steven Sevush School of Medicine University of Miami Miami , Florida , USA ISBN 978-3-319-33707-4 ISBN 978-3-319-33708-1 (eBook) DOI 10.1007/978-3-319-33708-1 Library of Congress Control Number: 2016947045 © Th e Editor(s) (if applicable) and Th e Author(s) 2016 Th is work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifi cally the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfi lms or in any other physical way, and trans- mission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Th e use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specifi c statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Th e publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. Cover illustration: © Th e Science Picture Company / Alamy Stock Photo Printed on acid-free paper Th is Palgrave Macmillan imprint is published by Springer Nature Th e registered company is Springer International Publishing AG Switzerland Foreword Th e question posed by this book is very simple yet very perplexing. When we look at a red rose, where exactly in our head are the mental events that give rise to that sense of redness? And if there were any doubt that this sensed redness is concocted inside the head, rather than outside, think of that viral smartphone snap of the blue and black—or was it white and gold?—dress. Th e colours we sense may track refl ectance or transmission properties of patches of the outside world quite well, most of the time. But if the tracking can fail we know we must be getting an internal mock- up, not ‘the outside world itself’. As Newton understood well, colours are ‘phantasms’ manufactured inside by brains and we want to know where. We want to know the neural correlates of consciousness. I t is sometimes suggested that thoughts and sensations have no particular position in space. What seems more likely, however, is that this is just a false inference based on the fact that we have no machinery for tracking where ideas are inside us in the way we do have for things we can see or pick up, like red roses. (We do seem to have internal time tracking.) In the same way, a police speed-trap camera can happily report to us the plate number of the car going past but cannot report where its hard drive is in relation to its light sensor because it has no device to sense that. Th at is no reason to think that the signals that indicate the plate number A675 RFT is passing by are in no particular place inside, even if, for other r easons, we may suspect that there is no sense of redness inside when it is a fi re engine passing. v vi Foreword Th ere are even those who claim that the redness is neither in the rose nor in our heads but in our ‘active’ interaction with the world. Suffi ce it to say that such theories have problems explaining quite what active interaction with the world is involved in hearing the doorbell ring unex- pectedly, or dreams and afterimages, or why certain drugs in overdose make the world blue or yellow. Moreover, without specifying that any particular internal event is necessary for a particular sensation, they are almost certainly untestable and therefore outside science. Th e redness must be in the brain, and to understand how it comes about we want to know where. Strangely, although a lot has been written on this subject in the last 20 years, very few authors have grasped the nettle of how to produce a solution that makes physical sense. At least a proportion of people pick- ing up this book will, like myself, already have a bookcase devoted to the topic of consciousness, sporting names like Crick, Penrose, Damasio, James, Edelman and Dennett. Whether you do or do not, it does not matter, because this book is diff erent in one crucial respect. It asks the question ‘how could that actually work?’ And this goes beyond narrowly defi ned physics—it is the question we ask as children when faced with a conjuring trick. We have a basic sense of things having to join up. Strangely, apart from Steven Sevush, most neuroscientists in the fi eld seem to have lost sight of that. Th e recent resurgence of interest in studying how the ‘mind’ works owes a lot to a rather unlikely duo of champions, Stuart Hameroff and David Chalmers. Hameroff has pursued a detailed biophysical investiga- tion into the fundamental physical events in brains that might constitute consciousness. Chalmers asked the question ‘but why would that be con- scious?’ Another prominent fi gure, Christof Koch, has replied ‘no idea, but don’t worry, it will be obvious when we have the answer’. Sevush’s approach seems to me to be much more powerful. Given the known structure of the brain and the fact that we can admire a red rose, he asks what sort of story could link the two that would actually work in terms of our basic understanding of cause and eff ect. I should declare an interest here. Over much the same period as Sevush, I have, independently, come to a very similar conclusion about how the brain gives rise to experience. We have encountered the same issues and Foreword vii resolved them the same way. My approach, however, has focused on the more abstract questions about causality. Sevush can reasonably regard many of my arguments as ‘fi lawsofy’, as Richard Feynman called it. He is interested, as a neurobiologist, in how the link from brain cells to redness could work in practice. Moreover, he insists on seeing how it could work at all levels of structure and function. Very often, theorists of conscious- ness will work at one level or other—focusing on molecular physics or nerve networks or computational issues. Sevush wants a story that will make sense in practical terms all the way down from cortical lobes to fun- damental physics. He may not have defi ned every step in full detail but he analyses each level closely enough to establish if it could actually work. Sevush’s approach has a long and venerable history, dating at least back to Hippocrates. It is amusing to refl ect that the supposedly great and ven- erable Aristotle made a pig’s ear of it in comparison, suggesting that the brain cooled the blood. William James perhaps most famously in modern times attacked the problem and concluded that there was simply no pos- sible answer consistent with physics. He bottled out. Th at is not good enough for Sevush. Th ere has to be an answer, even if common sense at fi rst seems to suggest it is impossible. F rom what I have said it might seem that this book has a rather dry agenda: more engine stripping than poetry. I hope not to give that impres- sion. Sevush is motivated by the rose as much as any of us: the marvel of experience. It is just that he wants to know how the marvel works. After all, the rose itself, in all its splendour, grows eff ortlessly out of the possibilities laid down by the laws of nature we now understand quite well. Surely the redness should be the same sort of marvel? Leibniz had the idea that perfection was the generation of maximum richness from the simplest of reasons. Th e simpler the reasons, the more marvellous the result. It is very fashionable these days to think that mysterious things like experience ‘emerge’ from complexity. But all too often that seems to be a smoke screen for ignorance. Sevush would ask: ‘but how could that work?’ Th e explanation for the redness of the rose given in this book will, I am pretty sure, prove puzzling and maybe inconceivable to many readers. As I have written in the past, it is the most diffi cult idea I have ever come across. It is diffi cult because it challenges our conception of our selves viii Foreword much in the way that Wallace and Darwin challenged the uniqueness of the human animal. If you might have thought the idea of having a mon- key as an ancestor was an aff ront then you may be in for a tough time here. It is not so much that others have not produced similarly belittling theories. Daniel Dennett almost denies your very existence as a human subject or ‘mind’. What is diff erent here is that Sevush accepts that there are real human subjects, but places them, one each, inside a vast number of cells in a particular part of the brain. Th ere is no single ‘me’, even if it seems that way. Again, this idea is not in itself new. Elizabeth Anscombe suggested long ago that each human being might contain multiple expe- riencing subjects. Th e diff erence is that Sevush gives reasons why this is the only reasonable interpretation of neurobiology and thereby con- fronts us with a practical possibility rather than a rhetorical philosophical question. T o build a theory of experience with this degree of depth and breadth in neurobiological terms is a pretty impressive achievement. Th e story is well worth reading. London Jonathan C. W. Edwards 15.3.2016 Introduction One Friday in December E very book has a story behind the story. Th e tale for this book begins on a Friday in December, three weeks before the millennium. It had been many years since I fi rst embarked on my quest to understand conscious- ness and I was beginning to face up to the sad truth that my eff ort had grown cold, with little chance of rekindling. Th en, a colleague at the University of Miami invited me to attend an informal discussion on con- sciousness that was to take place that afternoon in the philosophy depart- ment on the main campus. I usually avoided making the several mile trip to the main campus but I decided in this case to make an exception. Good decision. Not because of the discussion that took place at the meet- ing but for what happened after the meeting broke up. Th e discussion focused on philosopher Charles Siewart’s new book— an abstract philosophical work defending the position that conscious- ness is a signifi cant construct, not just an epiphenomenon. In attendance were four or fi ve philosophers, two neuroscientists, and me, a behavioral neurologist. I was both impressed and distressed by the interchange. I was impressed by Siewart’s mental acumen—he was just fl at-out smart. I was distressed by everyone’s familiarity with terms and ideas that were unknown to me. Clearly, I had been out of the loop for a long time. ix
The list of books you might like
