Hierarchical Brain

Perception

A perception takes place when a symbol schema is activated as a result of the processing of incoming sense data.

Perception is a higher level of description of the afferent processing of incoming data because it requires the existence of symbol schemas. For this reason, it is part of level 6 in my hierarchical structure of levels of description.

Overview

• A perception takes place when a symbol schema is activated to represent the thing being perceived.
  • This happens all the time subconsciously; a perception only comes into conscious awareness when the symbol schema is connected to the self symbol schema by the process of attention.
• Prediction and memory are both involved in the processing of the perception, which means that what is actually perceived is the best fit, or most likely thing, not necessarily what is actually there, and also that a perception is always influenced by previous experience.
• A perception can generate feelings, emotions, qualia and meaning only if the perception is conscious. This is done by the process of reinstatement, the reactivation of sensory neurons that were activated when the symbol schema was created or updated.
• Psychologists have understood for many years that perception is much more than simply the receiving and processing of sense data signals¹, but involves the reactivation of previously-stored memories from potentially many senses².
  • Afferent processing describes how incoming sense data is analysed for coincidences using a hierarchical and recursive process, which can also be viewed as compression. This results in the creation and maintenance of symbol schemas, and prediction is part of this process.
  • Once a symbol schema has been activated, representing the thing being perceived, there will be automatic reinstatement of sensory neurons via previously-created efferent connections from that symbol schema. Research using fMRI scans has shown this to be the case³.
  • Other connected symbol schemas may also be activated, and there may be reinstatement of sensory neurons from these as well.

Details

• The following diagram is based on afferent processing example 3, and is also very similar to one shown in reinstatement - the three functions are very closely related to one another.
  • It shows the seeing of a frisbee, the activation of the symbol schema that represents a frisbee via the afferent links (the overall flow shown by the large black arrow at the top), and the automatic reactivation of sensory neurons via existing efferent connections, in this case a memory of having previously thrown a frisbee (the overall flow shown by the large red arrow at the bottom). The two large arrows together show a loop of firing neurons that can continue for a short time.

• Please see diagram information for general information about my diagrams. The dashed lines to the hand throwing the frisbee indicate that this action happened in the past, it may have been days or weeks before.
• This example is just a very small part of what would typically happen before conscious perception of the frisbee. In reality, many different memories may be activated, via various efferent connections from the symbol schema, from previous encounters with a frisbee. These might include other visual or audio memories, ones of touch or proprioception (as in the example above), and even ones involving feelings and emotions⁴.
• When my eyes focus on a frisbee, the reactivation of previously-activated sensory neurons happens completely automatically and unconsciously, before I am even aware of what I are looking at.
  • If my attention is not directed onto the frisbee symbol schema, then all the loops of firing neurons between the symbol schema and the sensory neurons will die away quickly (in a fraction of a second) and, although any new or strengthened afferent and efferent connections may be retained, no episodic memory of the seeing of the frisbee will be kept.
  • However, if my attention is directed to the frisbee symbol schema, the loops in the top half of the diagram above will be strengthened and become part of a much larger network of firing neurons connected to the self symbol schema.
  • With conscious effort, my attention can also be directed onto previous memories of the frisbee, although some may not be available to attention. So some reinstatements may have an effect on how the frisbee is perceived, but I may not be consciously aware of why or how.
    • An example of this might be an emotional connection: I might feel happy or excited to see the frisbee because of an enjoyable time I had playing with it previously, but the conscious memory of this may be vague or non-accessible.
    • At the other end of the emotional spectrum, if I have had a bad experience in the past associated with the frisbee, I may suddenly feel fearful, or upset, without knowing why.
  • This influence of unconscious experience and memory on my perception, and therefore on my decisions and judgement, could I think explain quite a few puzzling so-called cognitive biases when humans behave irrationally for non-apparent reasons. This might include unconscious biases and even learnt phobias.
• The first time I see (or sense in some other way) a particular thing, it has no meaning attached to it. But once a symbol schema is created to represent the thing, it can then have associations, memories, feelings and emotions attached. When I next encounter the same thing, these connections will be triggered and be active before conscious perception of the thing happens, if indeed it does.
• When combined with prediction it is clear that I perceive things not based on what is actually there, but on what my brain thinks is most likely to be there. This, in turn, is based on my past experience and learning.
  • A good example that emphasises the way this processing works is provided by cases when an individual has a sense restored after they have been deprived of it for a long time. For example, a person who has been blind since birth or early childhood, and whose sight is restored later in life, finds that it takes a long time before they can start to recognise things in their new visual world, and that they find they have to make conscious guesses as to what they are seeing, because the establishment of symbol schemas and their connections takes months if not years⁵.
  • Perceptual illusions provide good evidence for this view of perception. When I perceive something incorrectly, it shows that the perception is decided before my consciousness has any knowledge of it or influence on it, and is largely predictive.
  • In the last twenty years or so, new theories have proposed that prediction plays a more fundamental role in perception, action and attention - see Predictive Processing for details.
• Music perception is another area that this may help in explaining.
  • It is very difficult, if not impossible, to explain to someone in words what it is about a piece of music that is good (or bad), beautiful, stirring etc..
  • If a person has been deaf from birth, then gained their hearing and listened to a piece of music for the first time, it would mean nothing at all to them.
  • The connections, feelings and emotions are only built up over many years of listening to this piece and perhaps other similar ones; but the crucial thing is that these connections are subconscious.
  • Obviously, it is possible for pieces of music to trigger conscious memories or connections as well; there are several pieces of music I can think of that, when I hear them, I am immediately reminded of a particular journey or place, because I have an emotional memory connected with them. But I think there are many other subconscious memories I have connected to music that are impossible for me to bring to conscious attention.
• This may also be the source of beauty in art, expertise in wine-tasting, hunches, gut-feeling, intuition and many subconscious decisions.
• As input to attention, and using prediction, perception provides a major part of the selection process that governs what is brought into attention. High-level prediction can provide a level of confidence about its prediction, and then, depending on the match with the signals coming in, can amplify the signals.
• The so-called “hard problem” of consciousness relates to how we have feelings about our perceptions, and also how those feelings are recalled when recalling the perception.
  • I think the explanation of perception given here goes a long way to explaining this - the feeling of a conscious perception is due to the self-awareness and therefore self-reflection possible within the self symbol schema along with the qualia of previous encounters via reinstatement.
  • See also Knowledge argument - “Mary’s room” thought experiment⁶. If a person sees the colour red for the first time ever, it will mean nothing to them, there will be no particular qualia, feeling or emotion attached to it. Later, after some time of experiencing red things, red wine, red sunsets etc., the colour will mean more to them and they will begin to experience the qualia similar to other people. So, merely to sense the colour red is nothing special, but perception of the colour red, with many links to past experiences, feels like something.

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

1. ^ The Principles of Psychology - William James 1890
   viewable here, downloadable here: Volume I and Volume II or see GoogleScholar.
   Volume 2, Chapter XIX “The perception of 'things'”, first paragraph: “Any quality of a thing which affects our sense organs does also more than that: it arouses processes in the hemispheres which are due to the organization of that organ by past experiences.”
2. ^ Consciousness and the Brain - deciphering how the brain codes our thoughts - Stanislas Dehaene Viking Penguin USA 2014
   Page 72: “we do not hear the sound waves that reach our ears; nor do we see the photons entering our eyes. What we gain access to is not a raw sensation but an expert reconstruction of the outside world. Behind the scenes, our brain acts as a clever sleuth that ponders all the separate pieces of sensory information we receive, weighs them according to their reliability, and binds them into a coherent whole.”
3. ^ Convergent and Invariant Object Representations for Sight, Sound, and touch - Man, Damasio, Meyer and Kaplan 2015
   doi: 10.1002/hbm.22867 downloadable here or see GoogleScholar.
   Top of Page 2: “...information streams from the different sensory channels converge somewhere in the brain and form representations that are invariant to the input modality.” In other words, a representation of an object is somewhere in the brain and is triggered by sense data from that object no matter which sense is used.
   Page 11, last paragraph: “...we mapped the cortical representations of real-world objects presented in audition, vision, and touch. We found sensory representations in large sectors of the sensory and association cortices, and even in the early sensory cortices of modalities other than that of the presented stimulus.” In other words, perception of an object using one sense can trigger sensory neurons of other senses.
4. ^ See it with feeling: affective predictions during object perception - Barrett and Bar 2009
   doi: 10.1098/rstb.2008.0312 downloadable here or see GoogleScholar.
   From the Abstract on the first page [“affective” here means “related to feelings or emotions”]: “...the brain’s ability to see in the present incorporates a representation of the affective impact of those visual sensations in the past. ...The affective prediction hypothesis implies that responses signalling an object’s salience, relevance or value do not occur as a separate step after the object is identified. Instead, affective responses support vision from the very moment that visual stimulation begins.”
   From the Conclusions on pages 1331-2: “...personal relevance and salience are not computed after an object is already identified, but may be part of object perception itself.”
5. ^ Ibid. See it with feeling: affective predictions during object perception
   The introduction on the first page describes the case of a man who lost his sight at the age of three and had it restored forty years later.
6. ^ The puzzle of conscious experience - Chalmers 1995 (updated 2002)
   Scientific American April 2002, downloadable here or see GoogleScholar.
   Page 93: “...consider a thought experiment devised by the Australian philosopher Frank Jackson. Suppose that Mary, a neuroscientist in the 23rd century, is the world’s leading expert on the brain processes responsible for color vision. But Mary has lived her whole life in a black-and-white room and has never seen any other colors. She knows everything there is to know about physical processes in the brain - its biology, structure and function. This understanding enables her to grasp all there is to know about the easy problems: how the brain discriminates stimuli, integrates information and produces verbal reports. From her knowledge of color vision, she knows how color names correspond with wavelengths on the light spectrum. But there is still something crucial about color vision that Mary does not know: what it is like to experience a color such as red.”

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