Let’s explain away

3 Replies

What is the difference between explaining and explaining away? If I watch a magician do a trick and I witness some object appear from nowhere or simply disappear before my eyes, I of course want to know how these things happen. I want an explanation. But do I want an explanation of how matter can be created or destroyed or do I want an explanation of how the magician made it appear to me what matter appeared and disappeared in a flash? It depends on whether I believe that magic happens or whether I believe that magic is a misleading performance. So someone could say, “you have not explained the magic, you have just explained it away.” To this the answer is, “I have not explained the magic because it never happened and was an illusion but I have explained the actual events that caused the illusion.”

When Dennett published his book ‘Consciousness Explained’, the clever retort was that the book should have been called ‘Consciousness Explained Away’. There have been a few people lately explaining consciousness, that appear to be doing the same thing, explaining it away. Consciousness is not the problem – it is the insistent on a conscious mind that has to be explained away. As soon as people believe that they consciously think as opposed to being consciously aware of thoughts, then the problems occur. Wanting to know how we consciously think is like wanting to know how real magical magic happens. So it would be wise and reasonable to stop trying to explain how we have a conscious mind and concentrate on explaining how we are aware of our thoughts.

The latest explainer-away the I have encountered is a paper by Oakley and Halligan, Chasing the Rainbow: The Non-conscious nature of being, Frontiers in Psychology Nov 2017 here and a blog post by the same authors in Brainfactor, What if Consciousness is not what drives the Human Mind here . One of the first things they do is to change the names so that their meaning is clear. The contents of consciousness they refer to as the personal narrative and the experience of consciousness is a product of internal broadcasting resulting in personal awareness. The contents and experience are the result of a completely non-conscious system; they use the name non-conscious rather than un-conscious.

The model is illustrated by a figure – the Oakley-Halligan model. (click to enlarge)

“The schematic diagram shows all current CES functions and other psychological activities as non-conscious processes and their products. The most task-relevant of these psychological products are selectedby a Central Executive Structure (CES) to create an ongoing personal narrative via the process of Internal Broadcasting. This personal narrative is passively accompanied by personal awareness – a by-product of Internal Broadcasting. Some components of this narrative are selected by the CES for further transmission (External Broadcasting) via spoken or written language, music, and art to other individuals. The recipients in turn transmit (internally then externally) their own narrative information, which may contain, or be influenced by, the narrative information they have received. The CES also selects some contents of the current personal narrative for storage in autobiographical memory. The contents of external broadcasts contribute (via Cultural Broadcasting) to an autonomous pool of images, ideas, facts, customs, and beliefs contained in folklore, books, artworks, and electronic storage systems (identified as “Culture” in the Figure) that is accessible to others in the extended social group but is not necessarily dependent on direct interpersonal contact. The availability of culturally based resources is a major adaptive advantage to the social group and ultimately to the species as a whole. The CES has access to self- and other-generated externally broadcast content as well as to cultural information and resources, all of which have the potential to provide information that supports the adaptedness of the individual and to be reflected in the contents of their personal narrative. As a passive phenomenon, personal awareness exerts no influence over the CES, the contents of the personal narrative or on the processes of External and Cultural Broadcasting. In the Figure non-conscious process are identified in green and personal awareness (subjective experience) in blue.”

There is a great deal of interesting information and ideas in this paper – comparison of varies models, historical progress, clarification of the absence of conscious control, models of self. And I will probably write another post on some aspects. But I also have a couple of reservations. The authors seem to deal exclusively with human consciousness and put great stress on the social and cultural role of consciousness. I would have liked a little hint to how they thought other animals might differ. One might think from reading the paper that they thought other animals were not conscious. I also thought they played down the very important relationship between personal narrative and memory. I continue to suspect that one of the most important aspects of conscious awareness is in laying down memories. And one of the most important aspects of thought is the use of memory.

We can hope that there is much more coming to explain consciousness by explaining away the conscious mind.

Inner speech is close to uttered speech

1 Reply

There has recently been a paper in eLife by Whitford etal, Neurophysiological evidence of efference copies to inner speech, Dec 2017 doi 10.7554/eLife.28197.001, examining inner speech. They find it very similar to overt speech.

When we speak a series of motor commands are prepared and executed by the mouth, throat and vocal cords. Copies of these commands, called efferemce copies are used to predict what the auditory area will hear. This prediction is called the internal forward model. When incoming sounds match the prediction, the auditory area lowers its response to the speech. This efference copy mechanism applies to other motor commands and is why we cannot tickle ourselves. The sensory pattern that will result from an action is predicted so that self-generated sensory input is attenuated compared to input that is not self-generated. In the case of speech, the actual sounds are predicted and when input arrives at the right time that matches the expected sound, the sound is dampened. This dampening can be measured. The sounds result in a particular brain wave which has an amplitude that matches the volume of the sound and it can be seen in EEG traces. It is called N1 indicating that it is the first event produced negative wave. This wave has less amplitude for sounds in self-generated speech than for identical sounds that were not self-generated.

In their introduction the author say “…the central aim of the present study is to explore whether N1-suppression, which has consistently been observed in response to overt speech, also occurs in response to inner speech, which is a purely mental action. Inner speech – also known as covert speech, imagined speech, or verbal thoughts – refers to the silent production of words in one’s mind. Inner speech is one of the most pervasive and ubiquitous of human activities; it has been estimated that most people spend at least a quarter of their lives engaged in inner speech. An influential account of inner speech suggests that it ultimately reflects a special case of overt speech in which the articulator organs (e.g., mouth, tongue, larynx) do not actually move; that is, inner speech is conceptualized as ‘a kind of action’. Support for this idea has been provided by studies showing that inner speech activates similar brain regions to overt speech, including audition and language-related perceptual areas and supplementary motor areas, but does not typically activate primary motor cortex. While previous data suggest that inner and overt speech share neural generators, relatively few neurophysiological studies have explored the extent to which these two processes are functionally equivalent. If inner speech is indeed a special case of overt speech – ‘a kind of action – then it would also be expected to have an associated internal forward model.” The researcher show that thinking of a particular sound (such as ba) attenuates the N1 signal of an external sound if they are the same sound at the matching timing. The inner speech efference copy and its internal forward model are produced in inner speech and can dampen an external sound if it matches the internal one.

Here is their abstract. “Efference copies refer to internal duplicates of movement-producing neural signals. Their primary function is to predict, and often suppress, the sensory consequences of willed movements. Efference copies have been almost exclusively investigated in the context of overt movements. The current electrophysiological study employed a novel design to show that inner speech – the silent production of words in one’s mind – is also associated with an efference copy. Participants produced an inner phoneme at a precisely specified time, at which an audible phoneme was concurrently presented. The production of the inner phoneme resulted in electrophysiological suppression, but only if the content of the inner phoneme matched the content of the audible phoneme. These results demonstrate that inner speech – a purely mental action – is associated with an efference copy with detailed auditory properties. These findings suggest that inner speech may ultimately reflect a special type of overt speech.”

This probably explains the nature of ‘hearing voices’. If this mechanism failed and inner speech was not properly predicted, it would appear to be external speech. It would not be ‘owned’ by the individual.

Ancient Origins – a great book

Leave a reply

Ancient Origins – a great book

I have just read a book by Feinberg and Mallatt, The Ancient Origins of Consciousness – How the Brain Created Experience. It may turn out to be one of those classic books that cause a big change in accepted science. They tackle the ‘mystery of consciousness’ in a new way, a very biological way. The book ends with, “a satisfying and complete explanation of primary consciousness requires a confluence of points of view, necessarily including neurobiological, evolutionary, and philosophical arguments, each contributing important answers to the ‘hard question’. Perhaps one reason no one has solved it before is that it requires all three perspectives, including what happened over half a billion years ago.” I assume there will be many who find the book’s theory wanting because of they view neurobiological naturalism is impossible and believe normal science cannot explain consciousness. The authors brand of neurobiological naturalism has three postulates which the book documents:

1. “sensory consciousness can be explained by known neurobiological principles”

2. “sensory consciousness is ancient and widespread in the animal kingdom, and diverse neural architectures can create it”

3. “the philosophical issues of ontological subjectivity, neuroontological irreducibility, and the ‘hard problem’ can be explained by the nondissociable confluence of neurobiological and adaptive neuroevolutionary events.”

The book has changed my ideas in a number of ways. First to fall was my attitude to the idea of ’emergent properties’. I have viewed it as a hedge, a cope-out, and even a way to bring dualism back in disguise. This book describes emergence in a way that makes sense. In a layered hierarchy each layer is created from the layer below but is more complex with novel elements which are labeled as emergent. But the external constraints act primarily on the top layer which constrains the layers beneath it. Thus there is both control and innovation by both bottom-up effects and top-down effects. Yes, this arrangement does need its own name and is a typical situation in living organisms. “In living systems such as the human body, cells constrain their subunits (organelles) to work together, the tissues and organs constrain their cells to cooperate, and the entire body constrains its organs to team up, all to perform the many physiological functions needed for the body to survive. If the constraints were to fail at any level, the body would disassemble and die.” A particular type of layered hierarchy, nested maps of the sensory organs such as the retina, is the basis of consciousness.

My second change of thinking was about the nature of the Cambrian explosion. It had seemed to me that the changes between geological periods were caused by changes to the environment like a meteor strikes which kill off the dominant animals and plants and allowed the others to flourish. But the book makes a case of a change to some animals being the cause and not the result of the abrupt explosion 560 – 520 million years ago. The result was new lines of animals which have populated the earth ever since. Predators appeared for the first time and this resulted in an arms race between predators and prey. There were many adaptations, and among them, improved distance sensing: vision, hearing and smell. Anthropoids and vertebrates in particular evolved high mobility and brains that improved sensory processing. A key change was image forming eyes. These allowed topographical maps of the retina. The other senses in vertebrates (except smell) re-evolved from a new cell line, on the pattern of the eye and its mapping in brain. In the resulting hierarchy of topographical maps for the senses, consciousness evolved.

I had assumed that the source of consciousness was lower in the brain than the cerebrum but was surprised by the location. The book documents it arising first in the optical tectum (superior colliculus in humans) and later extending to the thalamus and cerebrum, 220 years ago in mammals. This move not only added more layers to the existing hierarchies and put the top layer in close proximity to the sense of smell and its related memory in the cerebrum. This was a major advancement for consciousness for mammals and later for birds. Again I had to change my view as I had thought that memory and consciousness were always tightly bound.

The book also traces the evolution of affective consciousness (feelings and emotions), just as old as sensory consciousness. What was news to me was the intermingling of interoceptive bodily senses and affective limbic feelings giving three strains of consciousness.

The authors point out that the experience that the brain creates is embodied, personal, and does not include information about its creation – and therefore is wholly subjective and unique to each being. How this is done, the mechanism, is available to objective investigation. The subjective cannot see the objective and objective cannot see the subjective. There is a gap and it cannot be removed but neurobiological naturalism can ‘bridge’ it. This conclusion was not new to me as I have always been suspicious of whether the ‘hard question’ was really a question at all.

It’s a great book.

 

 

Meaning of Consciousness – part 4

5 Replies

For each science there seems to be a naïve folk version. There was a folk physics that allows people to predict that movement of physical objects, and so on with other sciences. This is still seen in expressions like ‘sun rise’ and the spontaneous beliefs on young children. Nothing is as it appears and we get used to the new knowledge. The sky is not as we thought – the stars and sun and moon are not as we thought. The earth is round. Gravity, light, heat are all different then we assumed. Solid material is mostly empty space. The earth is old and constantly changing. Life uses ordinary chemicals and there is no special essence of life. Life evolves. Our naïve folk versions of the world and our bodies have slowly been replaced by better explanations. But we still use a folk version of how the brain works. The unconscious processes were only recognized in the last hundred years. The nature of the brain is still more unknown than known. We guess this by the rate of surprising revelations that appear in the science journals, even the anatomy is not fixed. We are in for a revolution in how we understand our brains and like the Copernican Revolution, Darwinian Revolution and many smaller revelations, it will turn ideas upside down. This is hard – some people got physically dizzy when they learned that the earth rotates – back in the day.

How does the subjective nature of consciousness arise in a physical system? Is it impossible, or ‘an emergent property’, or a normal everyday process? I will pass over the impossible, magical answer. There is a definition of emergent property that has to do with hierarchical levels of scientific theories which I think misunderstands the nature of scientific reduction. What it really seems to mean in practice is that the speaker believes in a material world (or wants to hedge on it) but cannot find a path from a material brain to a subjective experience. So the subjective experience sort of ’emerges’ like a virgin birth from the material world by some new process or whatever that we have yet to find. But that process of emergence is not an ordinary one. Because I am a materialist (no hedging) I am not interest in the weird unknown emergent property. I am looking for a normal everyday process to explain subjective experience.

There really is a gulf here. In 2014 a Russian called Volkov invited 30 people – 9 important western thinkers (including Dennett and Chalmers) and teachers and students from the Moscow State University on a tall ship cruise along southern Greenland. They explored together on land in the mornings and had seminars in the afternoon. The idea was to come to some consensus. They had a great friendly time and in the end not one of them had changed their mind. Not much has changed since then.

To me, once we accept that what we have in consciousness is a model of the world and ourselves in it, that none of it is direct knowledge of the world or of ourselves but a model, then we seem home-free. That is what we have – only a model of the world and a model of ourselves in that world. Who then is the subject that is experiencing these models? If we do not watch out we will have a person inside a person inside a person to infinity. We cannot have a little person watching the screen because they would need perception, memory etc. and would in their turn produce a brain with a screen, to be watched by…. Who is the subject that has the subjective experience? It seem obvious that it must be the model of ourselves that is experiencing the model of the world and ourselves in it. And what we remember is ourselves experiencing the world; we remember a ‘subjective’ experience. It seems so simple. I find this notion very comfortable and satisfying, but then I really do find mysteries unsatisfying.

I have found someone who puts forward this notion or one very similar and more complete and backed up with evidence, Thomas Metzinger. He has written a book called The Ego Tunnel, and in it he lays out a lot of evidence for the idea. He is a philosopher but works with neuroscientists.

But we still have a semantic maze. From our folk psychology, Freudian ideas, and philosophy through the ages, we have accumulated a map of our mental life. Belief, pain, and will are examples of mental vocabulary. There is a rule of thumb in science, ‘cut nature at the joints’. Don’t name entities that are not natural entities. Many of the mental words can slip over to be useful scientific descriptors, but perhaps not all of them. And they may change somewhat in meaning. Take freewill for instance: cutting at the joints, scientist find a progression that goes – goal, plans, intention, execution but there isn’t really a place for freewill except as a marked in consciousness for the whole completed chain that indicates ‘I own responsibility for this action’. To science freewill no longer means freedom to act without the physical restraints of a material world but only decision we are responsible for because they were not forced.

But here is some stubbornness like the people who insist that pain is only what we feel in consciousness, nothing in the brain can be labeled pain only the ‘subjective’ experience. I just hate semantic arguments, and they will go on and on as knowledge progresses and words move from be mental descriptions to being physical descriptions.

Then there is the question of qualia or the colours, sounds, smells of our consciousness. Many cannot accept the idea that the brain could produce qualia. We know that perception gives us the wherewithal to assign shapes and many sorts of characteristics (like colour, movement, texture etc.) to objects. So all that is needed is how the world is assembled out of the results of perception in the global work space (which is not actually a physical space but a process). Through evolution of hundreds of millions of years, this process has been tuned to help us notice what needs to be noticed, recognize what needs to be recognized, understand what needs to be understood. If someone has a better way of doing this than colour, pitch and the other bound characteristics, I would really like to hear it. That is the way our brains model the world and it is an excellent way – built for survival.

There are more unknowns than knowns in how ours brains work. There are lots of surprises to come. But I am happy with the framework I have to fit to ideas into. A non-mysterious, physical, material, and beautiful framework.

Meaning of consciousness – part 3

Leave a reply

What is the function of consciousness? Is the function thinking? There is type 1 thinking, unconscious thinking, and type 2 thinking, which we are conscious of. But it appears that what we are really conscious of is working memory, and not conscious of how an item is created and put in working memory. Type 2 thought is just unconscious processes using working memory as a tool for certain sorts of processing (some language, step-wise logic chains or calculations for example) and the contents of working memory are rendered into consciousness. If type 2 thinking is a function of consciousness then it implies that working memory is somehow dependent of consciousness.

We tend to associate moral responsibility with decisions made consciously, but for thirty of so years there has been growing evidence that we make decisions and execute actions unconsciously before registering them consciously. Libet’s experiment and its descendants just will not go away in spite of decades of trying. The notion that free will and ‘free won’t’ are functions of consciousness just will not work. What seems to be in consciousness is a metaphorical note saying, “I intended this action, I did it, and I morally own it.” There is a phrase, ‘fringe qualia’, which seem to be metaphorical notes about non-sensory information: states of mood and emotion, recognitions, ownership of actions and thoughts, important so take note, and so on. None of these arise within consciousness; they are add from and by unconscious processes. Consciousness can register responsibility for an action but not actually cause the action. There is a theory that consciousness is required to insure that there are not overlaps and gaps in motor plans. The idea is that the motor system needs a working model of the body and environment to proof its plans. This is probably true but not necessarily.

Is the function to give us a sense of self? The impression we have is that we are seeing the world through a hole in our heads around the bridge of the nose from about an inch and a half or so into the brain. But the ‘self’ is a complex mixture of what we control with our muscles, the sensory feelings from inside our bodies, sensory signals from the skin, our memories making a personal narrative, and very especially our consciousness. We naturally seem to identify with some sort of conscious ‘me/I’. Consciousness, as an awareness of ‘ourselves in the world’, has to create the watcher, listener, actor, that is in the world. Self seems essential to consciousness but not perhaps the central function.

Can memory be a function of consciousness? If we think about it, consciousness and memory do seem to go together, at least episodic memory. We remember things that we are conscious of and not things that we are unconscious of. We are aware we have been unconscious when there is a discontinuity in our memory train. It does not seem to require some sort of translation to bring a memory into consciousness – it appears to happen easily. It seems that imaginings are constructed of bits and pieces of memories and they also seem to fit into consciousness without effort. In order to remember experiences, we have to have experiences, and what is it that we experience – it is consciousness. the action. Consciousness can be experimentally tricked into being wrong, taking responsibility for actions the individual did not cause. But we are usually right. Knowing which actions we intentionally cause must be important to judging outcomes and learning from experience. Consciousness seems connected to various short-term memory systems: working memory, sensory memory, verbal memory. Episodic memory also is held together by a continuous self, all events and episodes happen to the same self. Consciousness may be what is prepared for episodic memory, the ‘leading edge’ of episodic memory, so to speak. Or it may be a monitor or newly formed memories, like the monitor head on a tape recorder. The creation of episodic memory would certainly be a function worth the biological cost of consciousness. Being part of the episodic memory system would fit with being an important anchor of the ‘self’. Even the metaphorical notes of the fringe qualia would fit it this episodic memory.

The question is – what exactly is the dependency of memory on consciousness. Episodic memory, imagination and consciousness seem to have the same basic nature or structure or coding. And this structure must be the vehicle of the subjective experience. I have looked for a clear statement of this idea in the literature and the closest seems to be the global workspace of Bernard Baars. He proposed a architecture that would give momentary active subjective experience of events in working memory, consciousness, recalled memory, inner speech and visual imagery.

Do other animals have consciousness? It certainly seems reasonable to assume that most vertebrates do. The source of the awake state comes from deep in the brain stem. Activity from there activates higher regions, the thalamus in particular. Awake, in animals, may not necessarily mean aware, but it would be wiser to assume awareness until proven otherwise, than to do as we have been doing, assume no awareness until proven otherwise. The cerebral cortex does not itself mount consciousness, it is done in partnership with the thalamus, probably be driven by the thalamus. It would seem that a rudimentary consciousness would be possible without a cerebral cortex. It has been found recently that split-brain subjects have one consciousness and not two. This implies that the source of consciousness is is not in the cerebral hemispheres, but must be in some lower region. But the vivid detail of the content must be from the cortex.

Still we do not have a explanation of the subjective nature of consciousness yet but that is for part 4.

 

Meaning of consciousness – Part 2

2 Replies

In part 1 a particular meaning of consciousness was picked out of the group of meanings. So what can be said about this neural idea of consciousness as simply awareness of self and surrounding world, here and now? Is it as it appears? Well, no.

To start with it is questionable whether it is a continuous stream, the ‘stream of consciousness’, as it seems to be. Instead It is likely to be discrete displays. A number of experiments (replicated a number of times) have shown that consciousness is not continuous. But there are also experiments that shown that it is not a straight forward series of frames as in a movie film. There is a fairly convincing in-between theory proposed by Herzag (PLOS Biol 2016). “We experience the world as a seamless stream of percepts. However, intriguing illusions and recent experiments suggest that the world is not continuously translated into conscious perception. Instead, perception seems to operate in a discrete manner, just like movies appear continuous although they consist of discrete images. To explain how the temporal resolution of human vision can be fast compared to sluggish conscious perception, we propose a novel conceptual framework in which features of objects, such as their color, are quasi-continuously and unconsciously analyzed with high temporal resolution. Like other features, temporal features, such as duration, are coded as quantitative labels. When unconscious processing is “completed,” all features are simultaneously rendered conscious at discrete moments in time, sometimes even hundreds of milliseconds after stimuli were presented.” They have a two stage model: a first stage of unconscious processing of features and the binding of these features to entities that ends after at least 400 milliseconds with a best fit solution and the triggering of the second stage of integration into a consciously perceived output. This precept is static but is labeled with features like colour, pitch and also duration, movement, location and the like. Although the precept is unchanging, it is experienced as having duration – as a slice of time although it does not exist for that duration.

This view of consciousness implies that we have no direct knowledge of how this conscious experience is created. We can report our conscious experiences but not how they were created or how accurate they may be. Introspection as a method of observing processes of thought is not a reasonable concept – it is not possible to interrogate the ‘mind’ subjectively, from the inside. “The human mind operates largely out of view, and yet people are unaware of their unawareness, confabulating reasons for their actions and preferences.” (Wilson Science 2008). Subjectively, creating consciousness is a transparent process. It can only be understood through objective study.

If perception is not done consciously and neither is motor control, exactly why do we need the conscious experience? It is almost like consciousness has no function – an extra that the brain does not need.

Chalmers put forward the distinction of the hard question and the easy question. This appears to be a new type of dualism, separating objective knowledge of consciousness from the subjective experience of it. There is an thought experiment called philosophical zombies. Why could there not be people who have no consciousness but who act the same as someone who does? This would mean that the function of consciousness in the brain does not include the experience of consciousness. The function of the easy part, the objective part, the neural part is separate from the function-less, hard, subjective, and mystical part. The core idea here is that a physical brain cannot produce a subjective experience, or if it does then it is by way of some special process that is not known to current science. It has been put forward that consciousness is a universal primitive like mass and everything has consciousness, or it ’emerges’ through some information theory mathematics in objects that are complex enough, or it is some product of quantum mechanics that has not been studied, or it is simply not physical but spiritual. So some people who try to explain consciousness are told that they have not explained it but ‘explained it away’ because the mystery is gone. And other people who try to explain consciousness are told that they have not explained it but made it a mystery because the physical world is over-stepped. This divide is unlikely to disappear in the near future. I have to say that I personally find it impossible to be a dualist. I want a physical explanation of consciousness, preferably in biological terms .

From my biological point of view, consciousness must have a function in the brain because it is very biologically expensive. It cannot just be entertainment. What function does experiencing ourselves in the world have? Does its reason of existence help explain it? That is for part 3.

Meanings of consciousness – part 1

Leave a reply

How little do we agree on what consciousness is? Not much. The word itself (in English) has a number of separate meanings: a type of awareness, such as ‘class consciousness’; awareness in an everyday sense, ‘they were consciousness of the fact that the room would be cold’; a personal awareness of the current moment, ‘his consciousness was filled with bright lights and music’; all mental activity that a person is aware of, ‘conscious self’. There are also meanings that result from translations from words in various languages, cultures and religions that might be translated into words like soul, mind, spirit, or a universal connection. The meaning that I want to concentrate on is the personal awareness of the current moment. But there are still many ways to view this particular consciousness – in spite of view points almost all people agree that they experience this idea of consciousness and assume that their consciousness is like that of others. And there is a general idea that the brain in particular is involved. It is at about that point that the agreement stops.

Until recently Descartes’ notion of consciousness was generally accepted: the mind/consciousness/soul was spiritual and the brain was physical so that animals, with only a brain, were automations without consciousness, thought or feeling, while, humans had a soul/consciousness/mind as well as a brain. How this human dualism might actually be possible, was a puzzle that philosophers worked on for several hundred years and some are still engaged in the riddle. Dualism is now almost gone from science – consciousness is something that the physical brain does by physical processes in neuroscience. I say almost gone because it often creeps back under various guises into the scientific literature.

Given a physical consciousness, the next fork in the road was an question around mind. Freud had made popular the idea of a brain holding two minds, a conscious mind and an unconscious mind. (This is a simplification of his very elaborate theoretical structure.) These two minds were seen in a sort of opposition, with the conscious mind wearing the ‘white hat’ and the unconscious mind wearing the ‘black’ one. There was little known of neuroscience in Freud’s time and his theories are built with entities that we now think of as features of minds rather than brains. Mind ideas are no longer associated with unconscious processes – simply any activity that does not appear in consciousness is considered part of the unconscious brain and no ‘black hat’ is implied. There is still the question of how much consciousness can be thought of as a conscious mind. But in order to side step this question, it has become more and more common to use the word ‘consciousness’ rather than ‘conscious mind’ and ‘unconscious’ or ‘non-conscious’ rather than ‘unconscious mind’. But when people say something like ‘in my mind’ they tend to mean ‘in my conscious mind’ in the Freudian sense. There is a mental vocabulary as well as a neural vocabulary – but to date there is no one-to-one mapping between mental entities and neural ones. There are two possible structures here: conscious mind can imply everything that is, was ever, or could be experienced consciously, a working mind creating thoughts and willing actions; or, consciousness can imply the mechanism creating and the specific content of a moment of conscious experience or awareness. These are very different pictures. The notion of a conscious mind is what underpins introspection as a method of getting direct knowledge of our thought processes. But it has been shown in many ways that introspection is not reliable. So my interest in consciousness is an interest in the momentary experience of the world and our existence in it – the simple conscious experience. All else is unconscious processing (also interesting but not as consciousness).

The indirect route

Leave a reply

There has been a bit of mystery around how different areas of the cortex initiate shared synchrony or seem to pass information between them.

A paper from a few years back (Poulet, Fernandez, Crochet, Peterson; Thalamic control of cortical states; Nature 2012) showed that the activity of the whiskers of mice affected the state of activity in the cortex. How did the whiskers affect the whole cortex rather than just the whisker sensory area? It was via the thalamus shown by producing the effect without whisker activity by stimulation of thalamus alone.

“We investigated the impact of thalamus on ongoing cortical activity in the awake, behaving mouse. We demonstrate that the desynchronized cortical state during active behavior is driven by a centrally generated increase in thalamic action potential firing, which can also be mimicked by optogenetic stimulation of the thalamus. The thalamus therefore is key in controlling cortical states.”

But that was a very general demonstration of thalamic control of large areas of the cortex. What about more specific action? A more recent paper, which uses a wide array of methods, shows a specific case (Wimmer, Schmitt, Davidson, Nakajima, Desseroth, Halassa; Thalamic control of sensory selection in divided attention; Nature 2016).

From their introduction: “Thirty years ago, Francis Crick proposed that the TRN (thalamic reticular nucleus) functions as a searchlight, directing the internal spotlight of attention to thalamo-cortical circuits that process ongoing behavioral demands. Due to technical limitations, this transformative model has been difficult to test, particularly under conditions where the attentional spotlight shifts. Our study combined novel and established technology to provide mechanistic details for Crick’s ‘searchlight hypothesis’. As such, we have taken important step in understanding the circuit mechanisms of sensory selection.”

The object/s of attention can come from bottom-up or top-down processes. In other words they can be triggered by perception or by cognitive and motor demands; triggered by external events or internal tasks. Top-down demands for attention to specific targets appear to originate in the frontal cortex and travel to specific areas of the sensory cortex making them more active. This paper shows that the information travels from the pre-frontal cortex to the appropriate sensory cortex area by way of the thalamus, via the appropriate part of the thalamic reticular nucleus.

Here is their abstract : “How the brain selects appropriate sensory inputs and suppresses distractors is a central unsolved mystery in neuroscience. Given the well-established role of prefrontal cortex (PFC) in executive function, its interactions with sensory cortical areas during attention have been hypothesized to control sensory selection. To test this idea and more generally dissect the circuits underlying sensory selection, we developed a cross-modal divided attention task in mice enabling genetic access to this cognitive process. By optogenetically perturbing PFC function in a temporally- precise window, the ability of mice to appropriately select between conflicting visual and auditory stimuli was diminished. Surprisingly, equivalent sensory thalamo-cortical manipulations showed that behavior was causally dependent on PFC interactions with sensory thalamus, not cortex. Consistent with this notion, we found neurons of the visual thalamic reticular nucleus (visTRN) to exhibit PFC-dependent changes in firing rate predictive of the modality selected. visTRN activity was causal to performance as confirmed via subnetwork-specific bi-directional optogenetic manipulations. Through a combination of electrophysiology and intracellular chloride photometry, we demonstrated that visTRN dynamically controls visual thalamic gain through feedforward inhibition. Combined, our experiments introduce a new subcortical model of sensory selection, where prefrontal cortex biases thalamic reticular subnetworks to control thalamic sensory gain, selecting appropriate inputs for further processing.”

It is worth considering the idea that most of the information flow from one part of the cortex to another, where there is no clear, direct nerve tract, is actually traveling by way of the thalamus.

Doing science backwards

Leave a reply

A recent article, (Trettenbrein, P. (2016); The Demise of the Synapse As the Locus of Memory: A Looming Paradigm Shift?; Frontiers in Systems Neuroscience, 10), questions what many consider settled science – plastic changes to synapses are the basis of learning and memory – may not be correct. Thanks to Neurosceptic for noting this paper (here).

“Actually, as of today, large parts of the field have concluded, primarily drawing on work in neuroscience, that neither symbolism nor computationalism are tenable and, as a consequence, have turned elsewhere. In contrast, classical cognitive scientists have always been critical of connectionist or network approaches to cognitive architecture.”Trettenbrein is in the classical cognitive scientist camp.

First Trettenbrein assumes that the brain is a Turing machine. In other words that the coinage of thought is symbols and that they are manipulated by algorithms (programs) that write to a stable memory and read from it. The brain is assumed to deal in representation/symbols as variables, stepwise procedures as programs and random access memory, giving together a Turing machine. “The crucial feature of a Turing machine is its memory component: the (hypothetical) machine must possess a read/write memory in order to be vastly more capable than a machine that remembers the past only by changing the state of the processor, as does, for example, a finite-state machine without read/write memory. Thus, there must be an efficient way of storing symbols in memory (i.e., writing), locating symbols in memory (i.e., addressing), and transporting symbols to the computational machinery (i.e., reading). It is exactly this problem, argue Gallistel and King (2009), that has by and large been overlooked or ignored by neuroscientists. …”

“Synaptic plasticity is widely considered to be the neurobiological basis of learning and memory by neuroscientists and researchers in adjacent fields, though diverging opinions are increasingly being recognized. From the perspective of what we might call “classical cognitive science” it has always been understood that the mind/brain is to be considered a computational-representational system. Proponents of the information-processing approach to cognitive science have long been critical of connectionist or network approaches to (neuro-)cognitive architecture, pointing to the shortcomings of the associative psychology that underlies Hebbian learning as well as to the fact that synapses are practically unfit to implement symbols.” So an assumption that we have a Turing machine dictates that it needs a particular type of memory which is difficult to envisage with plastic synapses.

I like many others believe, science starts with observations and moves on to explanations of those observations, or to state it differently, the theories of science are based on physical evidence. It is not science to start with a theoretical assumption and argue from that assumption what has to be. Science starts with ‘what is’ not ‘what has to be’.

Trettenbrein is not thinking that the brain resembles a computer in many ways (computer metaphor), he is thinking that it IS a computer (actual Turing machine). If the brain is an actual computer than it is a Turing machine, working in a stepwise fashion controlled by an algorithmic program. Then he reasons that the memory must be individual neurons that are – what? Perhaps they are addressable items in the random access memory. Well, it seems that he does not know. “To sum up, it can be said that when it comes to answering the question of how information is carried forward in time in the brain we remain largely clueless… the case against synaptic plasticity is convincing, but it should be emphasized that we are currently also still lacking a coherent alternative.” We are not clueless (although there are lots of unknowns) and the case for synaptic plasticity is convincing (as it has convinced many/most scientists) because there is quite a bit of evidence for it. But if someone starts with an assumption, then looks for evidence and finds it hard to produce – they are doing their science backwards.

Trettenbrein is not doing neuroscience, not even biology, in fact not even science. There are a lot of useful metaphors that we use to help understand the brain but we should never get so attached to them that we believe they can take the place of physical evidence from actual brains.

Just because we use the same words does not mean that they describe the same thing. A neurological memory is not the same as a computer memory. Information in the neurological sense is not the same as the defined information of information theory. Brain simulations are not real brains. Metaphors give resemblances not definitions.

Where is consciousness?

1 Reply

A particular type of epilepsy has been treated by cutting the corpus callosum, the tracks of nerves connecting the two hemispheres of the cerebrum. The result had very little side effects on the patients. However, with closer experimental studies, the nature of the split brain was examined. Only the left hemisphere spoke and so only stimuli presented to the left visual field resulted in spoken replies and responses of the right hand. The right hemisphere could understand written language presented to the right visual field and made responses with the left hand but never spoke. Based on this and similar evidence, it was assumed that there were two minds (that is two consciousnesses) in a split brain.

A recent paper has upset this hypothesis: Pinto, Neville, Otten, Corballis, Lamme, de Haan, Foschi, & Fabri; Split brain: divided perception but undivided consciousness; Brain Jan 2017. Here is the abstract:

“In extensive studies with two split-brain patients we replicate the standard finding that stimuli cannot be compared across visual half-fields, indicating that each hemisphere processes information independently of the other. Yet, crucially, we show that the canonical textbook findings that a split-brain patient can only respond to stimuli in the left visual half-field with the left hand, and to stimuli in the right visual half-field with the right hand and verbally, are not universally true. Across a wide variety of tasks, split-brain patients with a complete and radiologically confirmed transection of the corpus callosum showed full awareness of presence, and well above chance-level recognition of location, orientation and identity of stimuli throughout the entire visual field, irrespective of response type (left hand, right hand, or verbally). Crucially, we used confidence ratings to assess conscious awareness. This revealed that also on high confidence trials, indicative of conscious perception, response type did not affect performance. These findings suggest that severing the cortical connections between hemispheres splits visual perception, but does not create two independent conscious perceivers within one brain.”

When they showed an object in both visual fields and if the objects were the same or different, the split brain subject could not answer that question with either hand or by speech. They could not examine the objects together – so it was correct that the perception in the two hemispheres was separate and isolated. But if an object was placed in either or both visual fields, the subjects could say how many objects there were in total and there was no different in the answer coming from the left or right hand, or the voice. So although they could not examine the objects together, their consciousness covered the entire visual field – there was only one consciousness.

What can explain this if the results hold up? Perhaps the two hemispheres have learned unusual ways of communicating outside of the normal connections. Perhaps it is some dualistic magic. Or, to me more likely, consciousness is not a product of the cerebrum. It is created in some other part of the brain that can receive information from both hemispheres and can store its creation in immediate memory where it is available to the hemispheres. There is an obvious candidate, the thalamus. It is not cut in half by the cutting of the corpus callosum. It is connected to almost all areas of the brain and almost all information passes through it at some stage of its processing. It is the one part of the brain that must be functioning for consciousness to occur.

There has been for years an assumption that the cerebrum is the engine of thought and a number of things are puzzles because they cannot be understood looking at the cerebral cortex alone. It is time to thing about the possibility that the thalamus drives the cerebrum: it feeds information to the cortex, it creates the rhythms and synchronization in the cortex, and it controls the communication networks in the cortex. The thalamus may have the cortex as an on-line computer, to use that metaphor. But then the thalamus is in the center of the brain and the cortex is laid out on the surface. It is easier the examine the cortex and so the rest of the brain gets neglected. Like the man looking for his keys under the street lamp because the light is better there even though he lost them elsewhere.