Built-in Sat-Nav


Since the late 1800s, if someone wants to be a taxi driver in London they have to pass ‘The Knowledge’ and usually this means riding around London on a scooter for a couple of years or more, learning the city. During this time they learn 25,000 streets and all the landmarks, junctions etc. along them. They must know the best way to get from any A to any B within a 6 mile radius of Charing Cross. The qualification includes a written test and 12 or so oral tests. Then, after a few other checks, they can start to drive a London taxi. The question is – what does this do to someone’s head?

 

One result is a very large hippocampus. A ScienceDaily item summarizes some research on experienced London cabbies.

“The study showed that a region of the hippocampus was enlarged in London taxi drivers compared to the general population… the difference is linked to ‘The Knowledge’ of the city’s 25,000 streets built up by taxi drivers over many years…

Taxi drivers used the virtual reality simulation to navigate the streets of London whilst lying in an fMRI brain scanner. The researchers found that the hippocampus is most active when the drivers first think about their route and plan ahead. By contrast, activity in a diverse network of other brain areas increases as they encounter road blocks, spot expected landmarks, look at the view and worry about the thoughts of their customers and other drivers.

“The hippocampus is crucial for navigation and we use it like a ‘sat nav’,” says Dr Spiers from the Institute of Behavioural Neuroscience at UCL. “London taxi drivers, who have to know their way around hundreds of thousands of winding streets, have the most refined and powerful innate sat navs, strengthened over years of experience.”

In their study, Dr Spiers and Professor Maguire found that a part of the brain called the medial prefrontal cortex increased its activity the closer the taxi drivers came to their destination…Inside the hippocampus and neighbouring brain areas scientists have identified three types of cells which, says Dr Spiers, make up the sat nav. These are called place cells, head direction cells and grid cells.

Place cells map out our location, lighting up to say ‘you are here’ when we pass a specific place. There are thought to be hundreds of thousands of place cells in the brain, each preferring a slightly different geographical place. Head direction cells act like a compass, telling us which way we are facing. Grid cells … tell us how far we have traveled using a grid-like pattern akin to how we use latitude and longitude for navigation.”

 

Our whereabouts is something we are often very conscious of. Our consciousness also seems to never loss its spatial quality. Everything we are conscious of seems to have a location in our visual space or some other space.

 

 

Eureka

In a recent ScienceDaily item was a summary of Joydeep Bhattacharya’s work on the ‘eureka’ moment.

“Real-world problems come in two broad flavors: those requiring sequential reasoning and those requiring transformative reasoning: a break from past thinking and restructuring followed by an insight (also known as Eureka or “Aha!”), which is a process by which a problem solver abruptly, through a quantum leap of understanding with no conscious forewarning, moves from a state of not knowing how to solve a problem to a state of knowing how to solve it.

Despite its widespread reports, the brain mechanism underlying eureka is poorly understood. What happens in the brain during that particular moment? Is that moment purely sudden as often reported by the solver or is there any (neural) precursor to it? Can we predict whether and when, if at all, the solver will hit upon the final eureka moment?

In a new study led by Joydeep Bhattacharya at Goldsmiths, University of London, these questions were addressed by measuring brainwaves of human participants as they attempted to solve puzzles or brainteasers that call for intuitive strategies and novel insight. They detected an array of specific patterns in characteristic brainwaves which occurred several (up to eight) seconds before the participant was consciously aware of an insight. Right hemisphere was further found to be critically involved in transformative reasoning.

These results indicate that insight is a distinct spectral, spatial, and temporal pattern of unconscious neural activity corresponding to pre-solution cognitive processes, and not to one’s self-assessment of their insight or the emotional “Aha!” that accompanies problem solution. Further, this study also postulates that consciousness is like an emergent tip of an iceberg of neuronal information processing, and remote brainwave patterns could reveal the underlying structure leading to that emergence.”

 

It is interesting that conscious concentration on a problem can postpone the eureka type solution. As Richard Highfield’s Telegraphy article puts it, “Scientists have discovered why Archimedes had to relax in a bath before discovering his famous principle.” One might also say we know why Newton was relaxing under an apple tree or Kekule was falling off to sleep.

 

The stages that can be traced in combined behaviour, verbal reporting and brain wave measurements are: mental impasse including attention overload, relaxation of attention allowing the restructuring the problem, deeper understanding or insight into the problem and its solution, sudden consciousness of the correct solution or the insightful path to it.

Unconscious meaning


A Sciencedaily article, Scientists Watch As Listener’s Brain Predicts Speaker’s Words, is about the prediction of the next word to be uttered by a listener. This has a bearing on the question about how much of our language is conscious; it appears that it is probably similar to any other perception or motor aspect of our lives.

 

“Previous theories have proposed that listeners can only keep pace with the rapid rate of spoken language—up to 5 syllables per second—by anticipating a small subset of all words known by the listener, much like Google search anticipates words and phrases as you type. This subset consists of all words that begin with the same sounds, such as “candle”, “candy,” and “cantaloupe,” and makes the task of understanding the specific word more efficient than waiting until all the sounds of the word have been presented. But until now, researchers had no way to know if the brain also considers the meanings of these possible words…

‘We had to figure out a way to catch the brain doing something so fast that it happens literally between spoken syllables,’ says Michael Tanenhaus, the Beverly Petterson Bishop and Charles W. Bishop Professor…

‘Frankly, we’re amazed we could detect something so subtle,” says Aslin. “But it just makes sense that your brain would do it this way. Why wait until the end of the word to try to figure out what its meaning is? Choosing from a little subset is much faster than trying to match a finished word against every word in your vocabulary.’…

 

It seems that although language is most often present in our consciousness – that the cognitive work that is behind the use of language is not revealed in consciousness. The meaning of words is available without being made conscious. Meaning does not rely of consciousness.

The wrong question


Francis Crick and Christof Koch in Cerebral Cortex1998, Consciousness and Neuroscience, make the following observation about philosophers of consciousness.

“There is, at the moment, no agreed philosophical answer to the problem of consciousness, except that most living philosophers are not Cartesian dualist — they do not believe in an immaterial soul which is distinct from the body. We suspect that the majority of neuroscientists do not believe in dualism, the most notable exception being the late Sir John Eccles (1994).

We shall not describe here the various opinions of philosophers, except to say that while philosophers have, in the past, raised interesting questions and pointed to possible conceptual confusions, they have had a very poor record, historically, at arriving at valid scientific answers. For this reason, neuroscientists should listen to the questions philosophers raise but should not be intimidated by their discussions. In recent years the amount of discussion about consciousness has reached absurd proportions compared to the amount of relevant experimentation.”

 

They suggest that in two areas philosophers have raised important questions that have not been tackled by neuroscientist.

“The Problem of Qualia

What is it that puzzles philosophers? Broadly speaking, it is qualia –the blueness of blue, the painfulness of pain, and so on. This is also the layman’s major puzzle….

The Problem of Meaning

How do other parts of the brain know that the firing of a neuron (or of a set of similar neurons) produces the conscious percept of, say, a face? …Put in other words, how is meaning generated by the brain?…”

 

But are these reasonable questions? I suspect that Eliezer Yudowsky from Overcoming Bias with his Bayesian outlook would call these ‘wrong questions’.

“Where the mind cuts against reality’s grain, it generates wrong questions – questions that cannot possibly be answered on their own terms, but only dissolved by understanding the cognitive algorithm that generates the perception of a question.

One good cue that you’re dealing with a “wrong question” is when you cannot even imagine any concrete, specific state of how-the-world-is that would answer the question.  When it doesn’t even seem possible to answer the question.

Take the Standard Definitional Dispute, for example, about the tree falling in a deserted forest.  Is there any way-the-world-could-be – any state of affairs – that corresponds to the word “sound” really meaning only acoustic vibrations, or really meaning only auditory experiences?”

The problem of free-will


One of the aspects of new insights into the functioning of the brain that will be most disturbing to most people is the idea that ‘free will’ may not exist, at least in the way we have thought of it for a long time.

 

If we assume that the science is sound then:

(1) We spend time and effort in making decisions about whether and how to act. In other words, we do actually create an intention to act after a decision process.

(2) That intention results in action. The intention, the initiation of action and the action itself may or may not enter consciousness. There is not that much difference, if any, between a decision process that results in a totally unconscious action and one that is reported as a conscious action. Whether an intention is conscious or not seems to depend on whether or not we conscious focus takes it in.

(3) When the intention, initiation and action are registered consciously there is a time lag which implies that the conscious feeling of intent, initiation or action is not in any sense causal. A cause cannot happen before its effect. There is no even reliably enough time for a veto of action to be actually caused by consciousness.

 

To many people this seems to mean that they are some sort of automaton with no control over their actions and no responsibility for their behaviour. This idea of loss of control is enough to make people fight the idea that our decisions are not created in some sort of conscious ‘mind’. People can see themselves making decisions in some sort of conscious process and are not willing to lose that self image.

 

Kock and Mormann in a Scholarpedia article talk about the activity that is required to put an intent into consciousness.

“A particular aspect of the mind-body problem is the question of free will. The spectrum of views ranges from the traditional and deeply embedded belief that we are free, autonomous, and conscious actors to the view that we are biological machines driven by needs and desires beyond conscious access and without willful control. Whether volition is illusory or is free in some libertarian sense does not answer the question of how subjective states relate to brain states. The perception of free will, what psychologists call the feeling of agency or authorship (e.g. “I decided to lift my finger”), is certainly a subjective state with an associated phenomenal content (quale) no different in kind from the quale of a toothache or seeing marine blue. So even if free will is a complete chimera, the subjective feeling of willing an action must have some neuronal correlate.

Direct electrical brain stimulation during neurosurgery (Fried et al. 1991) as well as fMRI experiments implicate medial pre-motor and anterior cingulate cortices in generating the subjective feeling of triggering an action (Lau et al. 2004). In other words, the neural correlate for the feeling of apparent causation involves activity in these cortical regions.”

 

I have never been able to understand why people have a lack of identification with their unconscious thought. Why is it not their thought? Why are they not responsible for it? Why is it important to believe that their thoughts be made in a fictitious conscious process rather than a real unconscious process? Why distrust your own brain? What gives?

Feedback


We should look at feedback. Most explanations use something like a thermostat or a steam governor to illustrate this. The output is measured and its value affects the input to keep the output within a particular range. Room is too warm so heat is turned down, then room is too cool so heat is turned up. The human body is filled with feedback loops – blood sugar is too high so insulin is excreted then blood sugar is too low so insulin is cut off. With simple loops like this it is easy to follow the logic with your finger around the loop.

 

But as soon as you add a bunch of other feedback loops that share some of their inputs and outputs, overlapping loops, then the logic cannot be easily seen by following the loops with a finger. Overlapping loops can maintain a more or less stable state, but it is usually not the state that any of the individual loops would settle on.

 

These sorts of systems act a lot like iterative equations. Take a simple equation, x=2+squareroot(x). If we start with x=1 and put it in the equation then we get a new x, 2+squareroot(1)=3. If we take our new x=3 and put it in the equation then we get a new x, 2+squareroot(3)=3.73. If we take our new x=3.73 etc. we get a never ending series that homes in on 4. (1, 3 ,3.73 , 3.93 ,3.98 ,3.99) We can imagine this happening very quickly in a physical system. Equations like this generate series that either find a stable end point, or they oscillate between two values, or they run away to zero or infinity. Again this is a very simple example with one value, x, but imagine how difficult it would be to try to follow a large set of such equations with several overlapping unknowns.

 

So now look at the thalamus-cortex-thalamus loops. Every small place on the cortex has axons running to a particular small place in the thalamus, and thalamus axons run back to the same place on the cortex that sent axons to it. We have a billion or so loops. In the cortex each small place has loops with all its neighbouring small places. The same is true in the thalamus. Both maps also have some loops with places more distant then their immediate neighbours. This is what I have called MPOFBL, massively parallel over-lapping feedback loops.

 

How would a MPOFBL system act? It would be hard to say. One interesting type of behaviour is possible depending on the architecture of the loops. The system may oscillate and quickly stabilize on one particular state of activity pattern for the neurons. This state would be the best compromise of all the constraints of the architecture of the loops and the nature of the input (sensory and other). It might be thought of as the best-fit scenario for a model of the world. 

 

Here is the start of the PDP Primer by George Hollick. It is from about the time that the power of parallel processing started to be investigated as an important option. He is talking about an architecture that is similar but not identical to the thalamus-cortex-thalamus loops described above.

“In 1986, James L. McClelland, David E. Rumelhart and the PDP Research Group published a volume which was to become a seminal work in the field of cognitive psychology.

So just what is Parallel Distributed Processing (hereafter referred to as PDP) all about? Quite simply, proponents of PDP assert that the brain is NOT a computer, not a serial one anyway. In essence, thought is a parallel process, a network of multiple, graded constraints being considered simultaneously. Thought is not a single path of constraints being considered one at a time, as in conventional cognitive models. Moreover, structural differences in the network of constraints are important to the implementation of the thought process and can lead to qualitative differences in the final result. This is in direct opposition to previous cognitive theories which assert that structure has no effect on the outcome of the thought process.”

Grand Central Station


In the center of the brain is a little structure called the thalamus. It seems to be a center of activity and one of the places where four systems cross: sensory, activation, motor, limbic. Taber, Wen, Khan and Hurley start their paper, The Limbic Thalamus, with the following statement.

 

“The thalamus has been referred to as the “Grand Central Station” of the brain because virtually all incoming information relays through it en route to the cortex. In turn, virtually all areas of the cortex project to divisions of the thalamus. Thus, knowledge of thalamic anatomy and connections is critical in understanding thalamic influence on cortical function and in the interpretation of functional brain imaging studies.”

 

The first system is the sensory one. All the sensory information, such as that carried by the optic nerves, enters the thalamus (with the exception of smells). In the thalamus is a map of the retinas that receives the sight information. There is a map of the Corti membranes that receives the hearing information and a map of the body to receive touch information. Pain, visceral feelings and taste come to the thalamus. The sensory information that the cortex receives and processes comes via the thalamus. The axons that run from the thalamus to the cortex are matched by axons running in the opposite direction. Each small area of cortex appears to receive input from the thalamus and also to send its output to the thalamus. This is also true of the associative areas where two senses mix. The associative areas of the cortex are in two way communication with the associative areas of the thalamus. The thalamus also appears to have control over how parts of the cortex communicate with other parts of the cortex.

 

The second system is the activating one. The nervous system as a whole is the spinal cord and its extension into what is called the brain stem which has a number of structures attached to it, that we call the brain. In the brain stem is a structure called the activating reticular formation. This is an extremely ancient part of the brain. It seems to control the level of alertness: sleep, dreaming, wakefulness, alertness, fatigue, motivation. Waves of activation from the reticular formation seem to keep consciousness (or dreaming) going. When it is quiet, there is a deep sleep. If it is damaged so that it cannot maintain activation, a deep permanent coma results. This structure ends where it merges into the thalamus.

 

The third system is the motor one. Planning, initiating and controlling action is done by a system that includes the frontal cortex especially the pre-frontal, pre-motor and motor cortex, the basal ganglia and the cerebellum. The thalamus has a motor portion in communication with areas of the frontal cortex. This is two-way traffic as with sensory communication. The cortex can directly send signals to muscles but without modification these result in jerky movements. The cortex works with the basal ganglia and the cerebellum for fine control to give smooth movements. Cortex signals can go directly to the basal ganglia and the cerebellum but the return path goes through the thalamus. The thalamus is therefore one of the important elements of motor control.

 

Finally there is the limbic system which is primarily concerned with emotion, smell and memory.  It is not easy to list its components because different people have different borders to the area, but it at least contains the amygdala (chiefly associated with fear and anger), the hippocampus (associated by memory), the mammillary bodies (associated with memory), the hypothalamus (associated by drives and regulation of the internal body), the entorhinal cortex (associated with smell) and the limbic areas of the thalamus.

Input to the limbic thalamus comes from the amygdale, entorhinal cortex, septal nuclei and mammillary bodies. It is in mutually reciprocal communication with the parietal cortex, prefrontal cortex and cingulated cortex. The thalamus is also important to sensing and responding to pain.

 

It look very much to me, in fanciful moments, that the thalamus runs the cortex. I think of it as an ancient part of the brain that once was state-of-the-art in sensory perception and cooperated with other ancient parts of the brain to insure that responses were appropriate to situations. Then the thalamus got a brand new PC to use called the neo-cortex. The interaction between the thalamus and the cortex is probably the seat of consciousness.

 

What goes on in dreams?


With our senses more or less turned off, where do the conscious-like ‘perceptions’ of dreams come from?

 

Science Daily reported Nov 16 2007 on McNaughton and Euston’s research:

“…during sleep, the reactivated memories of real-time experiences are processed within the brain at a higher rate of speed. That rate can be as much as six or seven times faster (than) “thought speed.”

Memory stores patterns of activity in modular form in the brain’s cortex. Different modules in the cortex process different kinds of information – sounds, sights, tastes, smells, etc. The cortex sends these networks of activity to a region called the hippocampus. The hippocampus then creates and assigns a tag, a kind of temporary bar-code that is unique to every memory and sends that signal back to the cortex.

Each module in the cortex uses the tag to retrieve its own part of the activity. A memory of having lunch, for example, would involve a number of modules, each of which might record where the diner sat, what was served, the noise level in the restaurant or the financial transaction to pay for the meal.

But while an actual dining experience might have taken up an hour of actual time, replaying the memory of it would only take 8 to 10 minutes. The reason… is that the speed of the consolidation process isn’t constrained by the real world physical laws that regulate activity in time and space.

The brain uses this biological trick because there is no way for all of its neurons to connect with and interact with every other neuron. It is still an expensive task for the hippocampus to make all of those connections. The retrieval tags the hippocampus generates are only temporary until the cortex can carry a given memory on its own…

The initial creation of the tag is made through existing connections. In order to do the rewiring necessary to have the intermodular connections carry the burden takes time. What you have to do is reinstate those memories multiple times. Every time you reinstate the memory, the modules make a little shift in the connection . . . something grows this way, grows that way, a connection gets made here, gets broken there. And eventually, after you do this multiple times, then an optimal set of connections gets constructed…

His previous research has show that cells that fired during activity prior to sleep, also fired in the same sequential patterns during sleep. During sleep, the hippocampus sends little, 100-millisecond bursts of activity to the cortex as much as three times per second.”

 

This may be a way to explain dreams. There are other ways too. In this hypothesis, memories are first stored in a consciousness like form, a working memory. Then they are stored in a temporary form in the hippocampus, and then during sleep they are ‘replayed’ until they are stored in throughout the cortex. This ‘replaying’ produces dreams (at least if you are awoken during the process). The hippocampus probably has a limited capacity to store unconsolidated memories and therefore sleep is required at some point or the memories begin to be lost.

 

The hippocampus is essentially the edge of the cortex in the temporal lobe region and it is associated with two important functions: forming new memories / consolidating recent ones, and processing spatial information. People without an intact pair of hippocampi suffer anterograde amnesia, variable retrograde amnesia and an inability to navigate through a cognitive spatial map. 

 

Shared workspace


When we imagine something fictitious or remember something that happened, it is very much like experiencing it now. It is not an identical conscious experience but very similar. Things can slip from the future to the present to the past without much change in them. Even dreams, which are none of these things, seem to be constructed with the same building blocks. It is as if the brain uses the same workspace, tools, methods and materials whether it is constructing a fantasy, a forecast, a perception, a memory or a dream.

 

Two differences between dreams and the other experiences is that dreams do not seem to have the same narrative sense and they are not usually remembered. Sensory input is inhibited, action is inhibited and the brain seems to just free wheel in a state that is protected from the real world. What is going on is a mystery but probably it is a form of essential neural housekeeping.

 

Windt and Metzinger’s contribution to The New Science of Dreaming:

“…dreams are conscious experiences because they can be described as the appearance of an integrated, global model of reality within a virtual window of presence. From a purely phenomenological perspective, dreams are simply the presence of a world. On the level of subjective experience, the dream world is experienced as representing the here and the now. And even though it is a model constructed by the dreaming brain, it is not recognized as a model, but is experienced as reality itself. Put in philosophical terms, one can say that the reality-model created by the dreaming brain is phenomenally transparent; the fact that it is a model is invisible to the experiential subject.

Of course, the same point can also be applied to waking consciousness: even in wakefulness, our experience of the external world is mediated…since we never recognize that the reality-model experienced in wakefulness is, in fact, a model, we have the impression of being in direct contact with external reality – we live our lives as naïve realists. In this very general sense, the conscious experience of dreaming is no different from waking consciousness.”

 

The fact that waking consciousness must be turned off before dreaming consciousness begins and the fact that we cannot be conscious of more than one reality at a time in waking consciousness does imply that the same neural machinery is used to construct all types of consciousness.