You are currently browsing the thoughts on thoughts weblog archives for June, 2008.
- 28/12/2011: What is mind?
- 25/12/2011: Possible functions of consciousness 9 - marking agency
- 22/12/2011: Short-term memory capacity
- 19/12/2011: Possible functions of consciousness 8 - broadcasting waves
- 17/12/2011: half million total visitor mark passed on Dec 16
- 16/12/2011: Fusiform Face Area again
- 13/12/2011: Background links
- 10/12/2011: Possible functions of consciousness 7 - attention on the significant
- 08/12/2011: All that jazz
- 04/12/2011: the face of the sky
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Archive for June 2008
Living in the Present
24/06/2008 by admin.
In seems that we are conscious of an event a fraction of a second after our brains start to process the perception of the event. This is not surprising – we are conscious of the ‘finished’ perception and ‘finishing’ the perception takes time. The surprise is that we live in the present and not a fraction of a second into the past. How is this done?
There seems to be three possibilities:
- we live a fraction of a second into the past but never realize it.
- we play very weird games with the perception of time and simultaneous events.
- we do not live in the past but in a projection of the past into the future, giving an approximate present.
The last one seems the most useful to us and also may be a good reason to have consciousness. If the present is t0 and at that time the brain is constructing a model of the world as of t-x. This model is then run forward as a simulation through x duration of time so that it represents a simulation of t0. So we would be living in a simulation of the present. This gives a measure of error to prompt corrections of motor action and of perception. That would really be a cool system and well worth the effort of creating a single global model of the world accessible by all the systems of the brain.
It is not take much of a leap to go from thinking of a MPOFBL system (massively parallel overlapping feed-back loops) to thinking of a MPOFFL system (massively parallel overlapping feed-forward loops).
After writing the above but before posting it, I found a blog post on a NYTimes article. See article and blog. They discuss visual illusions that point to a projection into the near future. In particular the article talks about seeing an image before it actually happens.
“In an experiment originated by Dr. Nijhawan, people watch an object pass a flashbulb. The timing is exact: the bulb flashes precisely as the object passes. But people perceive that the object has moved past the bulb before it flashes. Scientists argue that the brain has evolved to see a split second into the future when it perceives motion. Because it takes the brain at least a tenth of a second to model visual information, it is working with old information. By modeling the future during movement, it is “seeing” the present.”
Posted in timing | 1 Comment »
The Brain-Computer Metaphor
19/06/2008 by admin.
We use a metaphor between brains and computers in a great many situations. This metaphor can be helpful but it can also mislead us. Brains and computers are very different and so any use of the brain-computer metaphor should be justified as useful, not just assumed to be so.
Some people assume that because neurons are either ‘firing’ or not firing, that the brain has a digital mode of operation. This is far from true:
- The rate of firing is often the most important aspect of a neuron’s activity and this is a graded activity and not an all or nothing one. A high firing rate gives a strong signal and a low firing rate gives a weak signal. This is not an on-or-off digital signal.
- The effect of a firing neuron on another neuron at a synapse can be to excite or inhibit the firing of the second neuron. So even in situations that are not graded, the signal is not binary.
- A neuron can have few to many synapses with another neuron and so the effect of one neuron on another is usually graded. This variable number of synapses changes with learning and forming memories.
- Other non-neuron cells (some glia cells) do not ‘fire’ but are probably always graded in their effects and take part in signaling in the brain in a not very well understood way. Glia out number the 100 billion neurons by 10 to 1.
- The timing of ‘firing’ of neurons can change the nature of the signal. Simultaneous firing is required for some effects. Timing effects may be graded.
- Neuron signaling happens in an environment of potent chemicals, electrical fields and magnetic fields. The effect of this environment is graded.
Posted in Uncategorized | 1 Comment »
Why not?
13/06/2008 by admin.
Why is redness red? Why not?
I’ve just been reading a ’97 paper by Ramachandran and Hirstein. They place the conscious experience with its qualia in the temporal lobe. They also give three laws of qualia and discuss the relationship between qualia and the experience of ‘self’. If you are at all interested in this subject, the paper is a must to read.
Posted in qualia | 1 Comment »
What do we know about consciousness?
12/06/2008 by admin.
Any hypothesis of the nature of consciousness has to address several facts – at least these facts, as a minimum, and there probably are other constraints as well as these.
- There is an intimate connection between memory and consciousness. We remember what we have been conscious of. We know we have been unconscious if there is a discontinuity in our memory of events. Memories ‘package’ experience in a form that closely resembles the conscious experience of events. We feel a flow of future projections to present conscious experience to past memories without any sharp change in the type of awareness.
- Consciousness and dreaming have some commonalities but are quite different in their connection to perception and action. Dreams are not about reality and usually not result in action and usually are not remembered.
- There is a time delay in the formation of a conscious experience which we do not perceive. It is as if we were automatons who, for no good reason, experience a continuous movie of our immediately past perceptions and actions. We feel our consciousness is a real time event when it is not. The best summary of the experimental evidence for the time delay that I have found so far is Roger Penrose’s review of the evidence.
- Consciousness is not a completely faithful model of what is actually happening. Illusions and misinterpretations are frequent and somewhat predictable. We do not even have a completely accurate model of our own minds. For instance: there are blind sight and other knowing-without-awareness-of-knowing; there are phantom limbs and other awareness-of-the-nonexistent.
- The way that conscious experience presents itself seems arbitrary and personal. Why is a particular wavelength of light seen as a particular colour? Is my red your red? Qualia (properties of perceptions) are an aspect of consciousness.
- Consciousness happens at the same time as some pronounced activities in the brain, particularly reciprocal communication between the cortex and the thalamus, low amplitude but high frequency brain waves, activity in the reticular formation. There is a summary in Scholarpedia but it is fairly technical.
- Our consciousness can be affected by various mental illnesses, drugs, stressful situations etc. We can also learn to modify our consciousness (with meditation for example).
We need a picture of consciousness that fits with and helps explain these facts.
Posted in AIMS | 1 Comment »
Living without a conscious mind
06/06/2008 by admin.
When I was young, I have no doubt that I believed in Santa Claus, the Easter Bunny and the Tooth Fairy. I stop believing in them early enough that I do not remember the event – but I do remember the feeling that it was important to continue pretending to believe in them. I have encountered that feeling since when I have given space to some idea that I thought was a harmless little sham, something comforting to say, an old reliable metaphor, a poetic licence.
It came as a real shock to realize that others believed a myth; it was like finding adults who believed in Santa Claus. The conscious mind as opposed to the subconscious mind was one of those ideas. Although it had never seemed to me that I had any more than one mind, it did seem polite to allow others to separate themselves slightly from their actions. They could appear more modest or more blameless if they were allowed to let their subconscious to take the praise or blame. Sometime in my teens, I began to call people on their ‘my subconscious did it’ remarks. To my surprise they believed they had this other mind inside them that was bent on sabotaging their intentions. The only picture that made sense to me was that I had one mind and it was in no way divided – this mind perceived, thought and acted – and I was conscious of some but not all of this activity.
So I had a mind and it was the only mind I had. If I had to choose between it being a conscious or an unconscious mind, I would have to say unconscious, although the choice is somewhat ridiculous. And I also had consciousness – not a conscious mind just plain consciousness. My consciousness seemed part of my mind but not involved with my perceptions, my thoughts, my decisions and so on. All it did was supply an awareness. I have lived the next 50 years with this self image.
The problem is that other people seem to have a very different self image that they are as sincerely about as I am about mine.
I am encouraged that more and more published material uses the term ‘consciousness’ rather than ‘conscious mind’ as time goes on. Here is John R Searle’s definition which does not imply that the thought process is a conscious process.
What we need at this point in our work is a common sense definition of consciousness and such a definition is not hard to give: ‘Consciousness’ refers to those states of sentience or awareness that typically begin when we wake from a dreamless sleep and continue through the day until we fall asleep again, die, go into a coma or otherwise become ‘unconscious’. Dreams are also a form of consciousness, though in many respects they are quite unlike normal waking states.
Posted in mind | 1 Comment »
Is the brain bayesian?
02/06/2008 by admin.
I was interested in a post on Mind Hacks about looking at the brain as a Bayesian probability machine. The aspect that got me was the modeling and the importance of prediction.
I was reminded of ideas that I wrote down in the early 80’s.
“We can view ourselves as having a nervous system with many functions, one of the major ones being the function of ‘mind’. The mind function consists of building, maintaining and refining a model of reality; using the model to predict, plan, decide, initiate and control responses to the world; storing an edited form of the model as a memory of experience for comparison and learning. During introspection we only have access to consciousness, the memory being formed, and not the model itself.”
The Mind Hacks post reviews an article from the New Scientist by Gregory T. Huang about the work of Friston and Hinton at
(Bayesian statistics) “asks the question ‘what is the probability of the belief being true, given the data so far?’. The NewSci article looks at the work neuroscientist Karl Friston, who increasingly believes that from the level of neurons to the level of circuits, the brain operates as if it uses Bayesian statistics. The essential idea is that the brain makes models upon which it bases predictions, and these models and predictions are updated in a Bayesian like-way as new information becomes available.”
Picture the brain’s circuits working to minimize the prediction error of a reality model and doing this by using feedback loops. I envisaged a different type of feedback (something on that in future posts) but the principle is very similar.
“Friston created a computer simulation of the cortex with layers of “neurons” passing signals back and forth. Signals going from higher to lower levels represent the brain’s internal predictions, while signals going the other way represent sensory input. As new information comes in, the higher neurons adjust their predictions according to Bayesian theory. This may seem awfully abstract, but there’s a concrete reason for doing it: it tells Friston what patterns of activity to look for in real brains.”
It is great to look forward to this and similar ideas being experimentally tested!!
Posted in modeling | 2 Comments »
Thank you
01/06/2008 by admin.
Before I start posting, I would like to thank three bloggers. Their combined effect on me this week was to result in my starting this blog.
Greta Christina’s Blog has a posting, Greta’s largely unsolicited advice on blogging, that has giving me courage to jump in the blogging water. Babel’s Dawn by E.B. Bolles has convinced me that big vague questions can be tackled using a blog to create a hypothesis and critically examine it. He is doing this with the evolution of language. I have him to thank for showing me how to be a useful blogger. And, the current piece in Mind Hacks about Bayesian aspects of thought is where I intend to start with my first posting.
THANK YOU all.
Posted in Uncategorized | No Comments »
Aims
01/06/2008 by admin.
Does the world need another blog? Well, I think so or I would not be starting this one. We need to talk about consciousness from a different angle. So… I will put forward various views that I find worthy of discussion and then I will hope that others comment on my pieces and other comments.
Consciousness is a big subject:
What is it?…..Why do we have it? –or- What is its function?…..How did we get it? –or- How did it evolve?…..Where is it? –or- What is its neurobiology?…..What does it feel like?…..Other questions will, no doubt, follow.
It is also approached in different ways – by scientists, philosophers, therapists and artists.
But there is the hope that consciousness is quite simple to understand and with that hope, I blog.
Posted in AIMS | 1 Comment »