Thursday, July 30, 2015

David Parker’s reply

David Parker has sent me the following reply to my ’Notes on the relevance of neurophysiology to self-knowledge’:

As I say, consciousness is not an aspect that I have thought much about, I think there are far more questions that we have to address at lower levels before we get to be able to deal with this.  Although there is the idea, Moravec’s paradox, that lower-level processes like movement and initial perceptual processes that have had a longer time to be refined by evolution are actually the most complicated aspects, with the more recent effects being simpler. Rodney Brooks claims that thinking that things like movement are simpler than cognitive effects reflects a bias of researchers, who in considering themselves intelligent consider things that they find challenging, cognition etc.. must be more sophisticated than things like movement which we can all, children and insects, do effortlessly.

I suppose I am a physicalist/materialist, which given my background is not a surprise, and this biases what I expect to the foundation for consciousness to be. I am happy to admit that our knowledge of nervous systems is still very primitive. Just as a late 19th century expert physicist or neurophysiologist would be shocked by the disciplines in their modern form, there is of course the chance that a century from now our knowledge of the brain will alter in ways that make our current attempts to understand as pointless as Descartes attempts to explain reflexes. Nevertheless, I will offer a reply that assumes that what we know about the brain now is sufficient to offer, in principle, a physiological account of consciousness.

I suppose one issue is to define what we mean by consciousness. A neurologist would have a different definition to a philosopher. Francis Crick, one of the people who worked out the structure of DNA, spent the last 30 years of his life on consciousness (obituary claims that he solved the problem of consciousness are simply hagiography). He wrote “ one should define it (consciousness). You do not win battles by debating exactly what is meant by the word battle. You need to have good troops, good weapons, a good strategy, and then hit the enemy hard. The same applies to solving a difficult scientific problem”. I think for many people this would seem trivially a very weak argument.

Could the brain be considered a control system that ensures survival given certain features of the environment? It combines direct concrete responses to the world, sensations, reflexes etc.., with an abstract representational model of the world that at least gives rise to awareness of the world and predictions of the consequences of actions etc... given the current state of the environment and the body. This abstract view is modifiable, and can exist in neural structures (the cerebellum is a prime site where these internal models are thought to form). Most of our day to day behaviour seems to be “automated”, we don’t need to be consciously aware of what we are doing, unless we force ourselves to do this or something happens that brings functions to attention. There may thus be a general control system that overseas various functions served by specific areas and keeps things running, with certain areas brought to focus as needs require. One aspect of brain damage after stroke or injury seems to be the loss of this automatic ability, things seem to be attended to by breaking it into parts rather than being generated as a smooth automated whole. Maybe this is what consciousness is, the ability to be aware of the internal (self) and external signals, to coordinate and adjust these signals in a way that preserves function in a self-organised manner; a set of structures, maybe the whole central nervous system, acting together to ensure correct function. This would differ to some higher-level command centre that sits at a peak, either corporeal or not.

Much of the neurobiological evidence focuses on the analysis of visual pathways. Cognition (and thus mind, if you consider this a fair link?) arises from anatomical and functional aspects: various people (Hubel and Wiesel, Semir Zeki, David van Essen) have shown how simple features such as lines, colours etc.. in the visual cortex arise from lower level processes in the cells and synapses in the retina (already at the retina there is a complex network with several uncertainties of how it works), and how these are used to form perceptions ultimately of the form and position/movement of objects in a visual scene. There is the idea of a “grandmother” cell (more recently the “Jennifer Aniston” cell), a hypothetical cell that is the final point  in the visual cortex processing hierarchy where all the features of dots of light, lines, edges, colour, form, movement, maybe also memory and emotional components, are integrated to give the conscious perception of a face. This is unlikely to be a single cell; we lose many neurons every day and if one cell was responsible we would randomly lose whole percepts. But it could be a network of cells, and when all the features of a grandmothers face, the memory, and the associated feelings are brought together the circuit is active and this gives rise to the thought or actual perception of that face. I realise that your question is “how” does that activity give this conscious feeling, and I have to say we don’t know – presumably we learn these associations and update them as a face changes with aging, and this learning is fairly accepted to reflect the laying down of a particular activity pattern in the cortex. So when that pattern is repeated either by a thought (a trigger from something internal or external, like Proust’s Madeleine), or by artificial stimulation of the cortex with current or a drug, that conscious image is retrieved. But again, without labouring the point too much, we are ignorant of the complete mechanistic details of how a fly flies, so we are some way off having the knowledge that we would need to address this question. So the scheme is far from complete, but maybe it shows a potential to reduce cognitive functions to physiology?

Problem of qualia, individual subjective component of perception. Schrodinger said, “The sensation of color cannot be accounted for by the physicist's objective picture of light-waves. Could the physiologist account for it, if he had fuller knowledge than he has of the processes in the retina and the nervous processes set up by them in the optical nerve bundles and in the brain? I do not think so”. I know that qualia, and philosophical zombies and other thought experiments etc..., are a major philosophical debate. I can’t do this justice in my ignorance, but I have never really got this. That I have a subjective impression of a “redness” of an object that is specific to me does not seem to negate physicalism, that this impression is formed from interactions between nerve cells, just as a perception of a straight line is formed that way. We maybe lack a way of explaining mental terms by references to physical properties, but this doesn’t mean we wont be able to.

The neurosurgeon Wilder Penfield reported that when he stimulated areas of the cortex the primary somatosensory areas resulted in location of a “touch” but higher areas reported more qualitative effects, being stroked by velvet/sandpaper etc.. Could this be a neural representation of a qualia, a subjective impression solely generated by neuronal activity? And we seem to learn these associations. Experimental studies and rare instances of feral/impoverished children show that without exposure to certain features within a critical period can lead to “blindness” to these aspects ( Penfield also had, albeit a small number of patients who reported that stimulation of the temporal lobes could give rise to vivid recall of memories, again suggesting a neuronal basis.

The brain does not completely determine behaviour. This reflects the interaction of the brain and body with environment. This applies to basic functions, reflexes etc…, and there seems no reason also why this may not also relate to consciousness. So maybe it is not enough to look inside a brain to explain this. The field of biosemantics views the mind as a product of an evolutionary history, and claims in this case nothing can be asked about the mind in the absence of this history. Maybe this muddies the water further, a collective consciousness of the sort that Jung proposed. Modern science in its reductionist fervour will not countenance these effects, everything is brain and everything in brain is neuron, but we clearly inhabit a world that impinges on us and alters our behaviour countless times a day. To say that behaviour, consciousness, psychiatric or psychological issues all come down to the biology of the brain seems untenable, but one that is difficult to critique in the current climate. The psychiatrist RD Laing had what I think is a good quote. He dealt with schizophrenics on a Glasgow psychiatric ward in the 1950’s. The expert view was that these patients were psychotic with no insight, and they were subjected to various “treatments”. Laing wrote of his experiences something like, “I am more troubled by the fearless power in the eyes of my colleagues than by the powerless fear in the eyes of the patients”. He later pushed the heresy further by actually talking to these patients.

The question of whether our perceptions are a reflection of the external world is a question that I suppose is impossible to answer, there is always the appeal to solipsism which seems impossible to negate in someone who argues we can never know what is out there. From the physicalist perspective, the outside world is physics, various types of electromagnetic waves and forces, chemicals etc.., that impinge on our senses. The interaction of this physical world with the physical world of our sensory receptors gives rise to physical effects in the nervous system. We know from neurobiology that what we perceive is a computed form of the exterior due to various stages of processing that filter out or emphasise various features – and sensation/perception isn’t a hierarchical ascending chain, sensory systems have at least as many descending pathways, i.e. from the cortical regions out to the sensory structure. Is it an accurate representation? I suppose here we could appeal to the fact that we can tend to agree on sensory experiences, albeit they can be idiosyncratic in terms of the quality of tastes, hues, smells, sounds, but these may be the individual learnt components I talked about above. Maybe a better appeal is that it seems to work, we all navigate our way through a sea of electromagnetic waves, forces, chemicals without accidentally banging into things, falling over, or poisoning ourselves.

Moravec (1988) had an interesting thought experiment. Imagine that a surgeon can replace a single neuron in your brain with a totally exact artificial version, and then successively did this for each neuron. At what point, if ever, do you stop being you? If everything could be replaced in total anatomical and physiological detail would you not be you? Even if the neural architecture led to some emergent non-corporeal consciousness then this would also be created by the artificial you. I find these thought experiments mostly unhelpful. For philosophical zombies I cannot get far into the discussion without thinking – but they don’t and wont exist.

From your comments on Notes on the relevance of neurophysiology to self-knowledge, I don’t know if there is a profound discrepancy between our physical brain and the world of our consciousness. I will grant that by appearance a brain may not seem capable of the effects that underlie our consciousness. Maybe the same could be said of just walking, running etc.., given the tremendous amount of processing that may be needed to control multiple joints and 100’s of muscle groups rapidly and precisely. Yet we know it does that. Whenever I see brains in anatomy classes I am struck by the thought that this structure somehow generated thoughts feelings, memories etc.. of that person, not that there must be a mismatch between this and our mental life. But that is of course looking at it through a physicalist lens. As I have said before, we are still in a primitive state of knowledge about the workings of even simpler brains, and we shouldn’t let our lack of insight eliminate the possibility that when we know more about its operations some of these issues may melt away.

You write, “…for the world we are conscious of is not interfered with by the physical processes in the brain, by the electrical currents and chemical transmitters generated by neurons”. I suppose this again comes down to our lack of knowledge, maybe all of our conscious processes will be represented by the activity of complex networks of neurons. But we do know that our consciousness can be affected by targeting the properties of neurons and synapses, anaesthetics and psychoactive drugs with opposite effects on consciousness for example. We can interfere with consciousness in various ways; detecting it, I suppose a group of doctors would agree or disagree strongly on whether someone was conscious or not, and maybe they could tell from EEG or brain scans, but I think this may be a trivial response to you as you are not referring to being awake or asleep but to more subtle aspects of consciousness. As I wrote before, we know that we can do things now that we couldn’t do 20, 50, 100 years ago, and we should be open to the idea that going forward in those periods of time we may know more. I am not saying we necessarily will make major steps forward and that we must eventually understand these effects, but we shouldn’t hold up our lack of insight now as a reflection that consciousness will forever be beyond physiological explanation? Neuroscientists do not help themselves here; they make great claims to understanding, or that this understanding will very soon be obtained, that treatments for various neurological and psychological phenomena will soon be in place, while all the time we know little that would satisfy any lay persons questions about how our brains do what they intuitively know they can do, and we can effectively intervene to do very little when the brain goes wrong. It seems that claims to understanding are inversely related to our actual understanding, which may be a reflection of a Kuhnian crisis, the field has not achieved anywhere near as much as it would like, and to hide this we cover it with ever more exaggerated claims to actual or imminent understanding.

As for emergent properties, I grant you that to some extent this is a term thrown around to “explain” complex effects, and I have done just this in my reply to you and you are right not to be impressed. I suppose the best way to define it is an effect that is not reducible to the component parts, some property that is incommensurate with its components. Maybe your example of typing of single cells and synapses in the visual and motor pathways would not be a good example, as while single cells/synapses would not explain this effect, by tracing the activity along the visual pathways, through association areas, and then to the different motor areas and ultimately out to the muscles, we could in principle provide a mechanistic account of the chain of activity from one cell to the next that explains how you can see the key you want to press, make that motor response, and check what you have typed on the screen. Maybe an emergent effect for consciousness could occur through the summed activity in neurons. This, we know, can result in a “field” around the active neuron, either through electrical effects or through changes in different ion levels as a result of activity. These are dynamic and non-linear, and depend on the anatomy of the system (so not just the activity of a cell and the resulting non-linear changes, but also the organisation of the local space around the cells, a space that can itself expand and shrink as a result of the activity, creating a highly dynamic and non-linear circular interaction, something that would be difficult to analyse experimentally or treat mathematically). These field effects, termed ephaptic to distinguish a less intimate association than a synapse – you will understand the etymology. They have received relatively little attention, but where they have been studied we know that they can influence neuronal activity. Maybe this is an effect that exists outside and beyond the basic cellular properties of the nervous system, detecting the summed activity in various areas, while not being located to any area, and in turn altering the state of the nervous system?

So, this is a list of several replies to your comments. I don’t know how useful you will find it, I reflect the possible physical basis, reflecting my background. As I have said before, what is needed is debate between different views that allow people to remove their blinkers – I find this discussion outside my day to day work useful: it makes me consider things I take for granted (e.g. throwaway references to emergent effects in a previous mail). Neuroscientists seem keen to emphasise what they know and what they can do, and hold onto current paradigms and ideas dogmatically. Claims abound: that in a decade (eight years now) the billion Euro Human Brian Project will create a simulated brain that is fully conscious and talking to us. It won’t, and while dissenters within the project are growing, sensible critique against this white elephant was already there. I don’t accept that psychiatric illness is necessarily biological, causality is difficult to show, and claims of genes or transmitters for this or that have had a troubled history and logical errors abound. I don’t see why our knowledge of the brain is so advanced that computers and robotic systems will threaten humanity, conferences seriously discuss this. If we made computing/robotic systems based on our knowledge these systems will not be a threat – the best robots look like they have Parkinson’s disease – I am sure we can agree that there are far greater threats than this to humanity that we could easily deal with. Scanning brains for employment or legal issues is suggested to detect personality and criminal intent, but is science fiction for the most part. And claims of drug-induced cognitive enhancement or application of neuroscience to schools is troubling given our current understanding– there are reasoned and useful ideas around language/math learning etc.. but taken out of control these could make previous applications of neuroscience seem reasoned (I attach a review from several years ago about neuroscience and society if you were interested in any of this things). We should do what I naively thought scientists did, present ideas for rational debate, address issues, fill gaps, and correct errors and change views when necessary. I have learnt to my cost, as you seem to have, that discussing uncertainties is not welcome (in raising issues in my field I was told “ have a family, you have children. You need a job. As things stand I will support you...” , I am lucky to still be in science, albeit funding my work myself to some extent). But when what we take as simple systems are currently beyond our understanding, claims that analyses and ideas/hypotheses are complete or beyond reproach seem bizarre, not critiques. Another quote: the 1990’s were termed the decade of the brain, on being asked to comment on this the neuroscientist Torsten Wiesel, I referred to him above, said something like “ we don’t need a decade, we need a millennium”. There seems a growing tide of people coming in who want to move away from the feudal system that we have. So I enjoy thinking about the issues you raise, although I may add little.

No comments:

Post a Comment