Hierarchical Brain

Thought and imagination

Thought and imagination, including planning, day-dreaming and night-time dreaming, all describe the same flow of activation between symbol schemas in my brain.

This concept is at the highest level in my seven-level hierarchical model because it depends on the existence of symbol schemas and the model of my world in my brain, and also on attention and consciousness. In fact, it is more than a dependency: the flow of my thoughts comes about simply because of the architecture of my model of the world and the process of attention, which is why a lot of the detail on this page is little more than a higher-level summary of the processing of lower levels.

Overview

• The process of thought has been defined to be the manipulation of internal representations of the world in the brain^{1, 3}.
  • However, I think the word “manipulation” implies that something is doing the manipulating, which is not strictly true, certainly not all the time.
  • So a better definition, in my terms, is that thought is the activation of symbol schemas in the brain.
  • Some activations are from external triggers, the perception of something, but most are internal activations caused by an activated symbol schema triggering another to become activated.
  • This continuous process of one triggering others goes on all the time, except perhaps in the deepest phases of sleep.
• At any one time, there are many symbol schemas active, but due to the selective process of attention, only one can connect to the self symbol schema at a time, so I can only be conscious of one at a time².
  • For the same reason, while I am awake, it impossible for me to not think of anything.
  • My attention is always on something because the symbol schemas that are active are always competing to progress up the hierarchy to connect to my self symbol schema.
• There is a delicate balance maintained in the brain between excitation and inhibition which means that the number of symbols active at any one time does not get too high, but also the number does not get too low (see chaos - model of my world for more detail).
  • The balance means that brain function is on the edge of chaos, or on the edge of criticality, meaning that a small perturbation can sometimes cause a large change.
  • Just one neuron firing can potentially deactivate one symbol schema and activate another one.
  • Maintenance of this balance is carried out during sleep, which is one of the reasons why sleep is a critical brain function.

Details of my proposals

• The mechanism of thought is a continuous process, with the activation of symbol schemas triggering others, so it is difficult to know where to start when describing the process. Here are four different starting points, each of which can be described at different levels:
  1. A perception of something outside or inside my body causes the activation of a symbol schema which becomes conscious.
     • At a lower level of description, data from external or internal senses is processed through the hierarchical levels of afferent processing to activate the symbol schema that represents the object being sensed. The processing then carries on up the hierarchy until it eventually connects to my self symbol schema to become conscious.
     • This processing includes prediction to match up the incoming signals to an existing symbol schema, and selection by attention, which includes lateral inhibition of the processing of other sense data.
     • Perception also uses efferent connections, which are pathways of connected neurons from the self symbol schema, via the symbol schema in question, back towards where the sense data came in, in the reverse direction from the way that the original sense data was processed.
     • This reinstatement means that memories and feelings, emotions and qualia from previous encounters with the same thing may be consciously recalled.
     • It also means that meaning attached to the object is brought into conscious awareness.
     An example of this is when I see a shiny red frisbee and it immediately attracts my attention, and it brings back happy memories of when I have used it before.
  2. A perception of something outside or inside my body triggers the activation of a symbol schema that does not become conscious, but it triggers the activation of other symbol schemas, any of which could become conscious at a later time through the selective process of attention.
     • At a lower level, data from external or internal senses is processed by the first few hierarchical levels of afferent processing and activates the symbol schema.
     • However, a second symbol schema is also active at the same time, and inhibitory signals from it means that it wins the competition, and the first one does not make it through the multi-level selection of attention to become conscious.
     • However, other symbol schemas that have many connections to the first activated symbol schema are also activated by those connections shortly afterwards, and one of them becomes linked to my self symbol schema and becomes conscious.
     • Symbol schemas that do not make it to consciousness may have reinstated links activated, but they have no effect because of the lack of a link to my self symbol schema, so I am not aware of any memories or feelings related to them.
     An example of this is when I am deep in thought about something, and then I suddenly become aware of a tune in my head, and wonder why, and then I realise that I must have just (subconsciously) seen something that reminded me of the title of that tune.
  3. Following the previous example, totally outside my conscious knowledge, continuous triggering by activated symbol schemas of others is going on all the time, and this can continue for a long time. At any point, any one of these thoughts may become conscious, and it seems to me as though a random thought has popped into my head.
     • At a lower level, many thousands of neurons are being activated all the time, some causing the activation of symbol schemas, and other causing inhibition and therefore stopping other symbol schemas from being activated.
     • At some point, the influences on attention from the various directions may suddenly be sufficient to connect one activated symbol schema to my self symbol schema, and an apparent random thought comes into my head.
     • Usually I cannot think of a reason why that connection may have happened.
     • In theory these flows of signals that cause flows of activations are determinable, but because of the chaotic and critical nature of the architecture, in practice the results are unpredictable. This means that a symbol schema can sometimes be activated because of a low-level random event.
  4. Finally, I can influence my attention and therefore cause a thought, memory or action.
     • My self symbol schema can activate an “internal” symbol schema (a symbol schema that is a subset of my self symbol schema created by cognoception) that represents a particular “external” symbol schema becoming conscious.
     • How this is done, and why I only have an influence on it, is described in the pages on attention and free will.
     • This may triggers the “external” symbol schema to become active, which could be a thought, a memory or an action, and this will usually then become conscious.
     • A thought will then typically trigger a chain of other symbol schemas, some of which will become conscious at different times.
     • A memory will also typically trigger other symbol schemas to provide a conscious memory.
     • An action will initiate a chain of symbol schemas resulting in a movement or series of movements.
• Imagination, planning, day-dreaming and night-time dreaming all involve exactly the same flows of activations as described above but do not involve any perceptions from external or internal senses.
  • Imagination includes planning and imagining potential futures, and when movements are “rehearsed” but not actually carried out. This is also what happens when watching someone else doing something, when reading “internally”, or when planning and imagining what to say in a future situation.
    • The mechanisms required for this involve the activation of the same symbol schemas that would be activated to carry out the actions.
    • However, neuromodulation is used to inhibit all motor neurons so that the action is not carried out⁴, but the possible results can be predicted.
    • Some people will know the experience of the failure of this inhibition, when, hopefully only very occasionally, they say something out loud that they thought internally and didn’t mean to say out loud.
  • Dreaming, whether day-dreaming or when asleep, is different in its connections to the self symbol schema.
    • When asleep, there are only very weak afferent connections from any active symbol schemas to the self symbol schema and no efferent connections from the self symbol schema.
    • Dreams, and some day-dreams are not remembered after the event because of this lack of connections.
  • Creativity, or creative imagination, is as a linking of symbol schemas in a way that is new or different from the way they were linked when they were created.
    • This could happen consciously, because the self symbol schema facilitates connections between any symbol schemas even if there is no direct connections between them.
    • It could also happen unconsciously, because of the possibility of a symbol schema being activated solely because of a low-level random event.
    • In either case, the new connections can be strengthened and consolidated during sleep.
  • Imagination could be described as internal attention; in the same way that attention feels like a choice as to what external event to focus on, imagination feels like a choice as to what internal thing to focus on. In fact, in both cases, the choice is being made subconsciously, and I become aware of it consciously afterwards (see starting point 4 above).
• Here is an example of imagination that is triggered, directly or indirectly, by something sensed in the real world.
  
  • If I see a frisbee from an unusual angle (perhaps an angle that I have never seen before), I could call it imagination that enables me to realise that it is the same object that I have seen before, and that it is actually circular.
    • The mechanism to do this is described in afferent processing, prediction and reinstatement. Reinstatement is the method by which symbol schemas are given a meaning, in this case to reinvoke some of the sense data encountered when I previously encountered a frisbee.
    • If it is an angle that I have never seen before, it needs a connection made in the self symbol schema to link it to the existing symbol schema for frisbee, as described in this example.
  • I could then imagine seeing it spinning through the air, and imagine how I would need to grip it and throw it to make it do this.
    • This is enabled by connections between symbol schemas and reinstatement.
  • Using the same mechanisms, I may then remember the time I enjoyed playing with a frisbee on a beach. This might invoke the feel of the warm sun, the hot sand, the sound of the waves, and so on. These are real memories, re-created with reinstatement, with emotional feelings attached.
  • Going one step further, this could trigger thoughts about potential future times when I might re-visit the same beach, with some friends or relatives who have never been there. I might even imagine what I would say to invite them to come. These are imaginings of possible futures which will also use reinstatement, but the connections will not be from real memories, so they will not have the same feeling about them.
  • One final further step might be to imagine something that is physically impossible, or at least never likely to be encountered, such as playing frisbee underwater, or on the moon, or whatever. These impossible scenarios will also use reinstatement, but the connections will be even less realistic.
• How do I know whether something is real or imagined?
  • Research has shown that there are cases, even in people with normal brains, where reality can easily be confused with imagination⁵ (also see Is it real or imagined? How your brain tells the difference), by setting up contrived situations where reality does match the imagination of a subject, but in real life this is quite an unlikely set of circumstances for most people.
  • It is clear that my neural activity will be quite similar in the two cases of seeing a frisbee and imagining seeing a frisbee, except for obvious differences in the first few levels of the visual processing hierarchy.
  • My perception of the frisbee only involves the activation of my symbol schema that represents a frisbee, whether it is real or imagined.
  • But the reinstatement links will be different between the real and the imagined cases, which is why the two situations ”feel“ different (see feeling).
  • The most obvious examples of this are internal bodily feelings; the difference in feeling between a real pain and imagining a pain are huge.

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References For information on references, see structure of this website - references

1. ^ Mental Models: Towards a Cognitive Science of Language, Inference, and Consciousness - Philip Johnson-Laird Cambridge University Press 1983
   see GoogleScholar.
   Page x (part of prologue), end of second paragraph to beginning of third: “...human beings construct mental models of their world... This idea is not new. Many years ago Kenneth Craik (1943) proposed that thinking is the manipulation of internal representations of the world.” (See reference 3 below.)
2. ^ Ibid. Mental Models: Towards a Cognitive Science of Language, Inference, and Consciousness
   Page ix Prologue first paragraph: “Why is it that we cannot think everything at once but are forced to have one thought after another? Our memories exist together, yet we cannot call them to mind all at once, but only one at a time.”
3. ^ The Nature of Explanation - Kenneth Craik Cambridge University Press 1943
   see GoogleScholar.
   Craik does not use the exact words that Johnson-Laird attributes to him in reference 1 above, but Chapter 5 entitled “Hypothesis on the nature of thought ” does have several statements that imply the same conclusion, although he is mainly describing prediction or planning rather than thoughts in general. See also The Nature of Explanation (a review).
   Page 51, first paragraph: “...this process of reasoning has produced a final result similar to that which might have been reached by causing the actual physical processes to occur.”
   Page 51, second paragraph, to page 52: “By a model we thus mean any physical or chemical system, which has a similar relation-structure to that of the process it imitates. By 'relation-structure' I do not mean some obscure non-physical entity which attends the model, but the fact that it is a physical working model which works in the same way as the process it parallels, in the aspects under consideration at any moment. Thus, the model need not resemble the real object pictorially; Kelvin’s tide predictor, which consists of a number of pulleys on levers, does not resemble a tide in appearance, but it works in the same way in certain essential respects - it combines oscillations of various frequencies so as to produce an oscillation which closely resembles in amplitude at each moment the variation in tide level at any place.”
   Page 57, fifth paragraph: “My hypothesis then is that thought models, or parallels, reality - that its essential feature is not 'the mind', 'the self', 'sense-data' nor propositions but symbolism, and that this symbolism is largely of the same kind as that which is familiar to us in mechanical devices which aid thought and calculation.”
   Page 60, second paragraph: “...our nervous systems do contain conducting sensory and motor paths and synapses in which there occurs states of excitation and volley of impulses which parallel the stimuli which occasioned them.”
   Page 61, second line: “If the organism carries a 'small-scale model' of external reality and of its own possible actions within its head, it is able to try out various alternatives, conclude which is the best of them, react to future situations before they arise, utilise the knowledge of past events in dealing with the present and future, and in every way to react in a much fuller, safer, and more competent manner to the emergencies which face it. Most of the greatest advances of modern technology have been instruments which extended the scope of our sense-organs, our brains or our limbs. Such are telescopes and microscopes, wireless, calculating machines, typewriters, motor cars, ships and aeroplanes. Is it not possible, therefore, that our brains themselves utilise comparable mechanisms to achieve the same ends and that these mechanisms can parallel phenomena in the external world as a calculating machine can parallel the development of strains in a bridge?”
   Pages 120-121, the concluding paragraph of the book: “..I have outlined a symbolic theory of thought, in which the nervous system is viewed as a calculating machine capable of modelling of paralleling external events, and have suggested that this process of paralleling is the basic feature of thought and explanation.”
4. ^ Free agents: how evolution gave us free will - Mitchell 2023, Princeton University Press.
   Also see Free agents (Google books)
   Pages 137, fourth paragraph, in Chapter 6 entitled “Choosing” in the section headed “Simulating possible futures”: “First, some action plans are conceived of in the cortex. Doing so may entail the activation of different set of neurons, with each specific pattern corresponding to a particular action plan. At this point, these patterns represent the idea of doing something, not a commitment to it.” The text goes on to describe the convoluted mechanism involving the area of the brain called the basal ganglia, which can (indirectly) cause inhibition of the motor areas of the brain via neuromodulation, and then also how other neuromodulators can play a part in promoting some plans over others, depending on the priorities of the thing needed to be done.
5. ^ Subjective signal strength distinguishes reality from imagination - Dijkstra and Fleming 2023
   doi: 10.1038/s41467-023-37322-1 downloadable here or see GoogleScholar.
   Beginning of discussion on page 6: “In this study we investigated how imagined and perceived signals interact to determine reality judgements. By combining large-scale single-trial psychophysics, computational modelling and neuroimaging, we find evidence in support of a theoretical model in which reality and imagination are intermixed to determine a unified sensory experience. This model runs counter to accounts in which imagery and perception are separable, and to earlier findings of the Perky effect which imply imagery suppresses perception of reality. When deciding whether an experience reflects external reality or internal imagination, our model compares the strength of this experience to a reality threshold. But if reality and imagination are subjectively intermixed by default, why do we not confuse them more often in daily life? We suggest that such confusions are rare simply because imagery is typically less vivid than veridical perception, rarely crossing the reality threshold. However, these results also suggest that if imagery does become vivid or strong enough, it will be indistinguishable from perception.”

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