29/07/2008 by admin.

Much as I enjoyed Jaynes’ book, The Origin of Consciousness in the Breakdown of the Bicameral Mind, I definitely did not agree with its conclusions. Even something that I do not accept can still have little gems in it. One image that has stuck in my memory after all of thirty plus years: Jaynes compared consciousness to the lighted spot of a flashlight in a dark space. The dark space was everything going on in our minds and the little spot of light was what we were conscious of at each instant. We are not conscious of what we are not conscious of. We are not even conscious of the huge extent of what exists in our minds unconsciously. I was reminded of this when looking at some of work of R. A. Rensink.

Rensink has developed a way to show that we are not always consciously seeing what we look at. As well as having something in our vision, we also have to focus our attention on it. It has to be both the focus of our eyes and of our consciousness. He has created pairs of pictures that differ only in some fairly large change - something like an engine being there or not there in the centre of a photograph of any airplane. If the pictures are alternately flashed at the viewer, the difference in the pictures is noticed by the movement/change sensing part of the visual system so that both the eyes and the mental attention go to the area of difference. But if the movement/change sensing process is disabled by putting a blank flicker between the two scenes as they go back and forth, our attention and sight is not drawn to the area of the change. Then we must search the images carefully for some time in order to see the obvious. It feels like we have the whole image in our consciousness but it is an illusion. We only actually ‘see’ what we attend to. Here are demonstrations of the effect.

In this paper, Rensink proposes that there are two structures that are prepared from our raw perception. One has everything (sort of) without the detail. The other has very few things (with only some aspects of them) but in great detail. The first is used to set the scene and direct attention, the other is the attended-to focus. You can have quality or quantity but not all of both.

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26/07/2008 by admin.

Most of the time it feels like we can know why we make the decisions we make and do the things we do. It feels like we have our reasons and we know them. But what we are actually doing is probably making very good guesses of why we do what we do. This may seem different but it is very similar to our perception of the outside world. The brain puts in the pieces that fit the best – very good guesses.

The interpreter, or perhaps interpreters, was postulated by Michael Gassaniga to explain the way the left hemisphere reacted to the actions of the right hemisphere in split-brain individuals. Here are a couple of paragraphs from his book, The Ethical Brain.

Over the past thirty years I have been studying a phenomenon that was first revealed during work with split-brain patients, who’d had the connections between the two brain hemispheres severed to relieve severe epilepsy. My colleagues and I weren’t looking for the answer to the question of what makes us seem unified, but we think we found it. It follows from the idea that if the brain is modular, a part of the brain must be monitoring all the networks’ behaviors and trying to interpret their individual actions in order to create a unified idea of the self. Our best candidate for this brain area is the “left-hemisphere interpreter.” Beyond the finding, described in the last chapter, that the left hemisphere makes strange input logical, it includes a special region that interprets the inputs we receive every moment and weaves them into stories to form the ongoing narrative of our self-image and our beliefs. I have called this area of the left hemisphere the interpreter because it seeks explanations for internal and external events and expands on the actual facts we experience to make sense of, or interpret, the events of our life.

Experiments on split-brain patients reveal how readily the left brain interpreter can make up stories and beliefs. In one experiment, for example, when the word walk was presented only to the right side of a patient’s brain, he got up and started walking. When he was asked why he did this, the left brain (where language is stored and where the word walk was not presented) quickly created a reason for the action: “I wanted to go get a Coke.”

 Of course, this guessing is only obvious under unusual situations. Ordinarily our brain has most of the information it needs to make a good estimate of the reasons for our actions and to create a reasonable narrative of our life for our conscious model. Unfortunately, we don’t know which bits are pure fictions.

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23/07/2008 by admin.

Our awareness of the world does not include smell in the same way as other senses are present. Most of the time our consciousness does not include the odours that surround us, even if we try to focus on what we smell. It is just not there to experience except if there is a really significant change in odour. For example, we know that houses have their own particular, individual smell but we only are aware of it when we enter the house. A few lungs’ full of air and the awareness disappears.

Nothing evokes a memory as effectively as an odour. But those memories seem to be of a place, a condition, a situation but especially a place.

Smell does not carry the identification of a moment in time, the way sight, hearing and touch do. Smell’s timing is like a smear, naturally so, for the odours linger long after their creation. It is about a place not an event.

It is possible, of course, to learn how to be aware of odours. Perfumers and wine tasters have each done it. And they have developed a vocabulary in which they can discuss and compare odours. This does not come naturally; professional noses have been trained.

The lack of awareness of odours does not imply that they are not important sensory input. This is illustrated by the paper, Subliminal Smells Can Guide Social Preferences, Dec 2007 issue of Psychological Science. Here is part of the Daily Science item on the paper:

“The acute sensitivity of human olfaction tends to be underappreciated. In general, people tend to be dismissive of human olfaction and discount the role that smell plays in our everyday life… Our study offers direct evidence that human social behavior is under the influence of miniscule amounts of odor, at concentrations too low to be consciously perceived, indicating that the human sense of smell is much keener than commonly thought.”

So we have a relatively good sense of smell. Not as good as dogs by a long way, but much better than we think we have. We are just less aware of it then we are of our other senses.

This lack of awareness is probably because of the way smell is processed in the brain. All the senses, bar taste and smell, enter the thalamus before passing on to the cortex. The sense of smell does not go directly to the thalamus but directly to the cortex. Not only that, the cortex that it does enter is slightly different from most of the cortex (more ancient and simpler).

The route through the thalamus is probably important to the feedback loops that I assume are basic to consciousness: important to the massively parallel overlapping feedback loops that stabilize on a model of the world.

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19/07/2008 by admin.

As everyone knows, even little children, moving pictures do not move. They are a series of very still pictures. But we make a movie from them in our brain. The question is how.

Surprisingly, sometimes we don’t. Some people with migraines have periods of ‘cinematographic vision’. It is like a movie run too slow so that there is the effect of little jumps between frames. The sufferers are not making the normal movement-effect in their perception.

So – maybe we do the movie trick all the time. Maybe our visual perception is a series of still pictures that are then made into a movie for our consciousness. 

When I went looking for info on this subject I happened on a paper by Walter J Freeman, A Cinematographic Hypothesis of Cortical Dynamics in Perception, University of California, Postprints 2006. It is not an easy paper for someone outside that specialty to read.  (found here) . Using EEG methods and sophisticated analysis, he was able classify spatial and temporal patterns. The abstract is below.

“The aim of this study was to measure and classify spatial patterns in sensory cortical EEGs relating to conditioned stimuli (CSs) in order to test the hypothesis, based on clinical reports, that cortical dynamics is not continuous but operates in steps that resemble frames in a cinema. Recent advances in the application of the Hilbert Transform to intracranial recordings of the EEG in animals have revealed markers for repetitive phase transitions in neo-cortex at frame rates in the theta band…The impact of a CS on a sensory neo-cortex reorganized background EEG into two types of sequential patterns of coordinated activity, initially local and modality-specific, later global. The initial stage of phase transitions required 3-7ms. Large-scale cortical activity then reorganized itself repeatedly and reliably over relatively immense cortical distances within the cycle duration of the center frequency of oscillation. The size, texture, timing and duration of the amplitude modulation patterns support the hypothesis that these frames may provide the basis for multi-sensory percepts.”

The paper identifies a phase transition that is localized to the primary sensory area with a carrier frequency in the gamma band and recurrence rates in the theta band (gamma packets). The later phase transitions that involve many sensory areas have carrier frequencies in the beta band (beta packets) and recurrence rates in the theta band. The activity is not continuous but in demarcated discontinuous patterns.

Another report that caught my eye was Working Memory Has Limited ‘Slots’ Science Daily Apr 7 2008 reporting work by Luck and Zhang. (here) 

Humans rarely move their eyes smoothly. As our eyes flit from object to object, the visual system briefly shuts off to cut down visual “noise,” said Steven J. Luck, professor of psychology at the UC Davis Center for Mind and Brain. So the brain gets a series of snapshots of about a quarter-second, separated by brief gaps… The working memory system smooths out this jerky sequence of images by retaining memories from each snapshot so that they can be blended together. These memories typically last just a few seconds, Luck said.

If the memory of our consciousness is individual frames then it is not unreasonable that the original consciousness was too. It takes time to create a perceptual model and when it is complete, it is stored. The creation of the next iteration of the model can then start. There is a process that morphs one into the next to give an impression of continuous movement.

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10/07/2008 by admin.

Why have a model of the world? The obvious answer is to allow us to act and react. If we do live in a model of the world, what would be needed in the model?

We need our environment in the model and this we get from our sensory perception, especially the distance senses: sight, hearing and smell. What we produce is a space with us at the center. We have some idea of what lies in every direction from that center and the movements and changes ‘out there’. The environment nearer to us or things we are manipulating come from these same senses but also importantly from perceptions based on touch (pressure, heat, pain).

Then we need to model ourselves in this environment. Again touch is important. But mostly we model our bodies from our sense of balance and acceleration and from the perceptions of posture and movement that we create from joint and muscle signals.

So now we have a model of ourselves in our environment but that is not enough to allow us to act and react. We are missing something. We don’t want something like a bunch of still photographs; we want a movie. We need a plot, a story line, a theme or a narrator. We need a structure that corresponds to the series of ideas: motivations – goals – plans – decisions - actions. So it would not be surprising if the model included a ‘theory of mind’ for our own behaviour.

We are assuming that we are dealing with a model. The physical tree is not actually in our model. Our model includes an item that models the tree. Our foot is not actually physically in our model. Our model includes an item that models our left foot. Our sitting down is not actually in our model. Our model of our body moving at sit in our model of a chair is being modeled. Forget about anything being physically present in our model; they are only represented in the model. A model is a model and what it models is what it models. They are not the same. There is reality and there is a model of reality – not the same thing.

Maybe you can see where this is going. Our decisions are just like everything else. They are not physically in the model and so they are not taken in the model, they are being modeled in the model. What we have in consciousness about our decisions is simply what has been modeled about them and nothing more. The model has to be fairly accurate or it would not be of much use. When we physically make a decision there is a high probability that it will be modeled along with the modeling of the consequential actions. But like everything else in our perceptions, the highly detailed, fine-grained modeling is reserved for those things that are the focus of our attention. We have much more awareness of some of our decisions then of others.

When we introspect we are not getting to know directly what is going on in our brains, we are just focusing attention on our model of our mind (not focusing on our mind, focusing on our model of our mind). That means our model has more detail of the processes of our mind but it is still the model and not the real thing. We understand our own mind a little more clearly then we do other people’s minds but not that much more directly. We do not real know how we take decisions because our neurobiology has not progressed that far. What we know is how each for us models our own decisions.

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04/07/2008 by admin.

There is a type of visual illusion that can be seen either of two ways – the vase or two profiles is one. (here) But it is very difficult to see it both ways at once. We seem to switch from one to the other. The two ways of seeing are in some sort of competition and there is always a winner and a loser but never a tie. Just thinking about one of the possible views is often enough to make a switch to that one.

I have taken this to be part of the workings of a MPOFBL system (massively parallel overlapping feed-back loops). It would stabilize on a ‘best fit scenario’ with a given set of inputs. But if the input is ambiguous, in this case designed intentionally to be as ambiguous as possible, there will not be a great deal of difference in the ‘fit’ of the two interpretations. The MPOFBL system can fall into either of the two scenarios with almost equal easy but cannot maintain both at the same time. So it flips between them.

There was a recent science daily report on work by Joel Pearson’s group at Vanderbilt, ‘Mind’s Eye’ Influences Visual Perception. They use a different method to force a choice between two perceptions.

“To test how imagery affects perception, Pearson, Tong and co-author Colin Clifford of the University of Sydney had subjects imagine simple patterns of vertical or horizontal stripes, which are strongly represented in the primary visual areas of the brain. They then presented a green horizontal grated pattern to one eye and a red vertical grated pattern to the other to induce what is called binocular rivalry. During binocular rivalry, an individual will often alternately perceive each stimulus, with the images appearing to switch back and forth before their eyes. The subjects generally reported they had seen the image they had been imagining, proving the researcher’s hypothesis that imagery would influence the binocular rivalry battle.”

It seems that in situations of ambiguity, we cannot maintain two differing perceptions, nor can we make one stable, and we flip between them. But adding some weight to one interpretation will make it the more stable one.

To me, probably because I cannot think of another mechanism, this switching between ambiguous perceptions points to an MPOFBL system.  

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02/07/2008 by admin.

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02/07/2008 by admin.

Well, it seems to me to be a rule of thumb in biology: if something has significant costs then it has significant function. Usually function is fairly obvious in our bodies but not with consciousness.

Some options are:

1. It has no function whatsoever. It can safely be ignored and is not necessary for our thoughts and action to be understood. Just relax, enjoy the show but don’t take it seriously.
2. It is a product of the process of forming memories. Memory has a function but consciousness by itself does not.
3. It is a method of different parts/modules/processes in the brain to communicate with each other. This assumes that our brains are so compartmentalized that without consciousness there would be not unity in our actions.
4. It is a model of the world created from our senses, memories, knowledge and in-born a priori concepts. We live and act within this model and have no naive direct knowledge of the world.
5. It is a model of the world created as above but projected into the near future. We live and act within this model but it is not time lagged and can be used to monitor actions by comparing the error between previous projection and current perception.

I am tentatively working on the assumption that consciousness is a model of the world that is the raw material for our memory and also a way to live in the present through projection for the near past into the near future and furthermore a global view that all parts of the brain can access if they require a global view.   

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