Hierarchical Brain

Reinstatement

Reinstatement is my preferred term for the reactivation of neurons that were activated when a symbol schema was created or updated, back towards the source of the data, often in the sensory or motor areas of the brain, when a symbol schema is activated. It is one of the high-level brain processes that form part of level 6 of my hierarchy of levels of description, and it depends on the existence of symbol schemas described in level 4.

Reinstatement is the process by which the higher-level functions of consciousness and attention provide feeling, qualia and emotions as well as the meaning attached to an concept, and involves the temporary inclusion of the representation of the concept into the self symbol schema, my representation of my self.

Overview

• Reinstatement is reactivation of neurons, often in the sensory or motor areas of the brain, when a symbol schema is activated.
  • A symbol schema is my name for a network of neurons that represents a concept in the brain.
  • When a symbol schema is activated (meaning most, if not all, of the neurons that make it up are activated), it causes signals to be sent back via efferent connections to neurons that were originally activated when that symbol schema was created or updated.
  • These reactivated neurons are back towards the origin of the data when the symbol schema was created or updated, which may be in sensory or motor areas of the brain, or they may be part of other symbol schemas, so it may trigger those symbol schemas to be activated.
  • The efferent connections were created or strengthened by afferent processing at the time of the creation or update and therefore maintain a record of that change; so the reactivation is a form of memory, but often not conscious memory.
• A number of other high-level features in level 6 depend on reinstatement, including perception and thought, and it is also a major facet of consciousness in providing feelings, qualia and emotions and meaning.
• Many different names and descriptions have been used by other writers for the same or a similar function, and even if you are not familiar with any of the terms, you are certainly familiar with the effects.
  • If you read to yourself, recall a tune in your head without actually singing out loud, remember the sound of someone’s voice or the noise that something familiar makes, or think of a familiar or evocative scene or place, then all of these require reinstatement.
  • It is the method by which things are recalled and the method by which they can have meanings, feelings or emotions attached to them.
  • Words we use like “reminiscent”, “redolent” and “evocative” are all describing the effects of reinstatement.

History and other names

• This term “reinstatement” was used by psychologists from the 1960s meaning the reactivation of a retained memory and/or emotion, particularly of a fear learned early in life¹. This is close to the meaning I am talking about here, but a much more general definition.
  • Much later, in the 2000s, the term was also used when evidence was collected that showed that neural activity seen when a memory was laid down was also seen in similar areas when that memory was recalled^{2, 3}. This was referred to as the “reinstatement hypothesis”.
  • In 2017, the term was used again showed that specific types of oscillations (caused by the firing of self-propagating neural circuits in the brain) were involved in the neural activity that was seen in both laying down a memory and the recall of that memory^{4, 5}.
  • The same term is used by psychologists with a very different meaning in connection with drug addiction, as in the reinstatement of drug-seeking behaviour.
• The neuroscientist Antonio Damasio used the term “retroactivation” in a paper in 1989⁶ to mean the reactivation of neurons near sensory and motor areas that were originally activated by an event when that event is recalled.
  • This meaning is very similar to my description here of “reinstatement” and references evidence for it, although the paper takes a very different approach from mine, starting from an anatomical perspective.
  • The term “retroactivation” has been used since, mainly with reference to the original paper, but does not seem to be widely used now, although it is quite a good name for the function.
• The rather curious term “redintegration” has been used in psychology to mean the recollection of a multi-sensory experience triggered by a single-sense event or thought⁷.
• The adjectives “embodied” and “grounded”, when applied to various nouns including “cognition” (see embodied cognition, for example), have been used to mean that a representation in the brain includes neurons in sensory and motor areas, which are reactivated when a concept or event is encountered or recalled^{8, 9, 10}.
  • This is very similar to my definition, except that I do not class the reinstated neurons as being part of the symbol schema.
    • My definition of a symbol schema is that it is the highest level of abstraction or generalisation of the concept that it represents, hence it does not include any neurons that were activated in lower levels of the hierarchy of afferent processing.
    • A symbol schema therefore does not necessarily change with every new encounter or recall, it is relatively static, although it can change if new information is discovered about the object or concept.
  • This does agree with my proposal that reinstatement is the only method by which symbol schemas gain meaning (but only when the symbol schema is consciously perceived).
  • The adjectives are useful because they describe the involvement of the body in the representation of meaning.
• Other terms or areas that are close to my definition include:
  • “Simulation”⁹ or “situated simulation”¹¹, meaning the recall of sense-related stimuli when a concept is recalled (although the word “simulation” has also understandably been used in other areas to refer to things like imagination or internal attention).
  • The simulation theory of empathy, situated cognition and mirror neurons are also concepts or theories that say that neurons in sensory or motor areas are activated when actions are seen, memories are recalled or actions rehearsed, all of which are encompassed by my proposals concerning reinstatement.

Details

• If I was a young child seeing a red frisbee for the very first time, I would not know what it was or what it was for, so the experience would have no meaning for me. Even so, automatic afferent processing would create or strengthen efferent connections to make a short-lived memory of this first viewing, which may only last a few seconds.
  • A simplified example of this is given in afferent processing example 1. It shows how links back towards sensory neurons that were activated when I looked at the frisbee are created or strengthened.
  • The memory exists because of a number of short-lived loops of firing neurons. This diagram, based on the final diagram in afferent processing example 1, shows the overall flow of signals in a loop. (Please see diagram information for general information about my diagrams.)
  • The dashed lines from the frisbee to the eye indicate that the sense data from the view of the frisbee is no longer incoming (I am no longer looking at the frisbee), but the flow of signals round the loop can continue for a short time after this, like an electric circuit.
  • This is the first and simplest example of reinstatement.
• With the typical curiosity of a child, during the second or so that the memory is active, I will probably look at this attractive red object from another angle, simply by moving my eyes or my head (and in fact this action could be driven subconsciously by the process of attention).
  • The same automatic afferent processing would create another short-term memory, and it would also create a connection from this to the previous memory.
  • This would cause a number of neurons and the connections between them to become a nascent symbol schema representing that frisbee, which could also be described as an invariant representation. How this could happen is shown in afferent processing example 4.
  • This new representation is a stronger memory that will last for longer, perhaps hours or days, but it only has meaning for me because it is linked back, via the automatically created efferent connections to sensory neurons that were triggered when I saw the frisbee.
• With multiple views, and perhaps input from other senses, which might include feeling it and attempting to throw it, a full symbol schema will be created. This diagram, based on afferent processing example 3 (please see diagram information for general information about my diagrams), shows the overall flow of signals that would happen when this symbol schema is activated in future. The dashed straight lines indicate that the sense data is no longer coming in.

• A symbol schema can be activated either via links from other symbol schemas, as a memory of the thing that it represents via internal attention, or when the same thing is perceived at a future time.
  • In both cases it is because efferent connections cause sensory neurons to fire that were triggered when I experienced the frisbee previously.
  • In the same way that perception uses reinstatement to give extra meaning to the experience, so also memories are given meaning through reinstatement.
  • It is because of reinstatement that a perception is never free of previous associations.
• So when I see a frisbee in future, this symbol schema will always be activated, which means that previous memories of the frisbee will be reinstated. These can include visual signals (what it looked like), proprioception signals (what it felt like and what it was like to throw it), and interoception (emotional signals indicating how I felt when I experienced it).
  • The word that philosophers use to describe the original experience, or feeling of something is qualia, so reinstatement re-creates, or perhaps simulates, to some extent, the original qualia.
  • The aspect of consciousness related to qualia and reinstatement is sometimes called phenomenal consciousness where the word “phenomenal” is being used in its technical sense of meaning “perceptible by the senses”.
• As outlined in the history section above, a large amount of research has shown^{4, 12} that the conscious recollection of a memory involves the reactivation of the same neurons that were activated when the memory was laid down.
  • The same research also confirms that the original creation of the memory and its later reactivation both require “oscillations”⁵ that involve a much larger network with connections to parts of the subcortical brain^{6, 13}, including the hippocampus.
  • The memories being investigated in these studies are episodic memories, i.e. memories of specific past experiences. Episodic memories require attention in order to be laid down (I don’t remember something if I am not paying attention to it), and the conscious recollection of a memory also requires attention, although of the internal variety.
  • Conscious attention always requires the involvement of what I call the self symbol schema, and therefore the encoding and recollection of episodic memories requires the activation of the self symbol schema. This could explain the involvement of the much larger network with connections to parts of the subcortical brain because the self symbol schema resides largely in the subcortical areas of the brain.
  • Attention requires “oscillations” (repeated firing of loops of neurons) because it is a relatively long-term event, and these oscillations involve the relevant symbol schema and the reinstated neurons as well as the self symbol schema.
  • The reinstatement of a concept feels like something in exactly the same way as the original experience felt like something, because of the involvement of the self-referential self symbol schema.
  • The self symbol schema is linked via efferent connections to the relevant symbol schema(s) and then via efferent connections to neurons that were involved in the original encoding of the memory. All efferent connections are created by afferent processing, as shown in afferent processing example 7.
  • This method of reinstatement is (in my view) the only possible way in which meaning can be manifested by the activation of a symbol schema in the brain.
• For abstract concepts, reinstatement must always be via related concrete concepts. Research has shown¹⁴ that abstract concepts are stored in an associative network. To take a simple example, the symbol schema for “danger” might be linked to the symbol schemas for “lion” and “snake”.
  • Even basic partly-abstract concepts such as “above”, “within”, “belonging to”, etc. can only be given meaning by relating them to concrete examples of relationships.
    • These relationships are efferent connections created at the time of afferent processing.
  • This fits with my own experience: when I think of an abstract concept, the only substantiation of it, i.e. the only meaning I can put onto it, is by relating it to concrete examples. However, for some basic concepts, I do not have conscious access to the relevant concrete examples.
    • I know that the capital of France is Paris, but I do not have conscious access to the memory of when I learnt that fact, but I must have had that memory once, so an episodic memory has turned into a semantic memory because the connection between the self symbol schema and the event in question has been lost; presumably it was pruned because it was not reinforced.
    • Similarly, I have a good understanding of the meaning of the concepts “within” (abstract concept) and “house” (concrete concept), but in both cases I do not have a conscious memory of how or when I learnt those concepts and, in the case of the abstract “within” concept, what it was related to.
    • So I believe that the reason must be the same: I had those memories once, but the connection from the self symbol schema to the remembered events were not reinforced, so were pruned.
  • It is also clear that language plays an important part in defining and understanding abstract concepts¹⁵. It would be very difficult to understand or use a concept such as truth or justice without the use of language.
  • So, in general, reinstatements of symbol schemas can lose their connections to the self symbol schema if not regularly reinforced, but they still exist, otherwise they would have no meaning to me. The meaning is only understood subconsciously, it cannot be called into consciousness. For a more recently acquired abstract concept, I may have a specific memory of how it is reinstated.
• The reinstatement of a symbol schema, implemented by many efferent connections, can be regarded as a property of that concept, thing or event, represented by other symbol schemas closely connected to the things or event, and the sense-related memories attached to them.
  • When the self symbol schema is connected to a symbol schema, it is almost as if that symbol schema temporarily becomes part of the self-referential self symbol schema, along with the properties of the symbol schema.
  • When I think of a frisbee, I can almost feel the wrist movement needed to throw it.
  • The neurons that are reinstated are part of what is often called the “early sensory cortices”, where this includes not only external senses, but also internal ones.
  • When I use an implement or tool, such as a knife and fork, a hammer, a tennis racket or a baseball bat, after some practice I can be aware that it feels like it becomes part of my model of myself while I use it.
  • You may also be aware that the same can be true for musical instruments, prosthetic limbs, mice and joysticks on a computer, and even the cursor on a computer screen.
  • In these cases, it is clear that the symbol schema for the implement or tool is not only joined to my self symbol schema, but is, in a sense, incorporated into it for a temporary period.
  • In the same way, but less obviously, when I look at and pay attention to a frisbee, it also in a sense becomes incorporated into my self symbol schema for a time: it feels like I have some ownership of it, or like I take possession of it.
• The quality of reinstatement, in conjunction with memory, clearly varies from person to person. There are genetic influences as well as environmental and learning influences on this.
  • Most artists must have a precise and detailed memory for visual scenes. This means they must have good reinstatement connections to the early visual cortices because, from memory, they can visualise a scene in great detail. A lot of this talent is inherent, but many people can learn to get better at this.
  • Most musicians must have a precise and detailed memory for sequences of sounds of particular types. This means good reinstatement connections to the early auditory cortices to enable them to hear, in their head, sequences of sound. A musician with perfect pitch must have particular reinstatement to pitch-specific neurons, which may be even nearer the incoming sound source than for most other people.
  • People with hyperthymesia (perfect episodic memory, also known as HSAM - Highly Superior Autobiographical Memory) or eidetic memory (photographic memory) clearly have much more persistent reinstatement connections to early sensory cortices.
  • The only people thought to have any real amount of photographic memory are a small proportion of children, aged up to about 12. This perhaps suggests that pruning of connections is the cause of the forgetting.
  • Some people with certain types of mental disorder, such as autism, have exceptional memories for certain types of things. Again, a part of this is due to genetic inheritance, but there are other factors. The connections from symbol schemas are clearly different, perhaps in their persistence or lack of pruning.
  • Hallucinations are a fault in the control of reinstated connections. Various hallucinations are a symptom of psychosis and auditory hallucinations (hearing voices) are a common symptom of schizophrenia, which is generally caused by a problem in the area of attention control and particularly salience.
• In Douglas Hofstadter’s book “Godel, Escher, Bach”, he suggests that meaning is created in the brain by the very perception of an isomorphism (a one-to-one matching) of symbols to the external world¹⁶.
  • I can see what he is suggesting, but he does not link this with self-awareness, although this is covered elsewhere in the book¹⁷.
  • If something is detected by our senses, but never comes into conscious awareness, i.e. is not connected to the self symbol schema and is not perceived, then it is not assigned any meaning. Meaning is given to symbols by reinstatement only when connected to the self-symbol schema.
• My description of how feelings come about includes emotion, qualia, pain and meaning, and reinstatement is involved in all of these.
  • Pain is a form of reinstatement, but it is also very similar to an emotion because the sensory neurons that are reinstated are within the self, and therefore via the self symbol schema.
  • So it could be said that pain is a price we have to pay for qualia: just as, when we see a frisbee we see it “out there”, rather than in our brains, so a pain in the toe is felt in the toe, not in the brain where it is being generated.
  • The word qualia tends to be applied to things with particular significance or levels of arousal such as the taste of a good wine, the view of a sunset or a photo of a deceased relative, but it could just as easily be applied to anything represented in the brain by a symbol schema.
  • When a concept is recalled, the feeling, or qualia, that was generated when it was originally experienced is, at least partially, re-experienced.
  • The extent or depth of this recall can vary; too much recall (going to a level too near to where the sense data came in) could be described as a flashback, or even a hallucination (see below); too little (not going near enough to where the sense data came in) would be considered a loss of memory, even though the symbol schema still exists. This loss of memory is probably what we all experience from time to time when we cannot remember someone’s name, or the word for something. The connections were there once but may have been pruned because they have not been used sufficiently.

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

1. ^ Reinstatement - Campbell and Jaynes 1966
   doi: 10.1037/h0023679 or see GoogleScholar
   First page, second paragraph: “By reinstatement we denote a small amount of partial practice or repetition of an experience over the developmental period which is enough to maintain an early learned response at a high level, but is not enough to produce any effect in animals which have not had the early experience.”
2. ^ Recollection and the Reinstatement of Encoding-Related Cortical Activity - Johnson and Rugg 2007
   doi: 10.1093/cercor/bhl156 or see GoogleScholar
   This paper refers to a “reinstatement hypothesis”. For example, page 2511, under the heading “Discussion”: “According to the reinstatement hypothesis outlined in the introduction, neural activity associated with the processing of an episode as it is encoded should be 'reactivated' when the episode is later recollected. The present study employed a design in which the neural correlates of encoding and later recollection could be directly compared within subjects. Consistent with the reinstatement hypothesis, regions where recollection-related activity differentiated test items according to their encoding history overlapped with some of the regions in which activity differed at the time of encoding. Moreover, this pattern of study-test overlap was selective; no regions were identified where recollection-related activity associated with items from a particular task overlapped with encoding-related activity for items from the alternative task.”
3. ^ Recollection, familiarity, and cortical reinstatement - a multivoxel pattern analysis - Johnson, McDuff, Rugg and Norman 2009
   doi: 10.1016/j.neuron.2009.08.011 downloadable here or see GoogleScholar.
   This interesting paper builds on the previous one (Recollection and the Reinstatement of Encoding-Related Cortical Activity) and concludes that episodic memories (memories of events in time) are stored in the hippocampus and include reinstated links, and non-episodic memories (memories of facts and procedures) are stored in the cortex and are reinstated from there. In both this and the previous paper, there is little reference to the reinstated areas being sensory or motor areas, but some of the other sources these papers reference make clear that they are certainly a relevant part of it.
   Summary, first page: “Episodic memory retrieval is thought to involve reinstatement of the neurocognitive processes engaged when an episode was encoded. Prior fMRI studies and computational models have suggested that reinstatement is limited to instances in which specific episodic details are recollected. We used multivoxel pattern-classification analyses of fMRI data to investigate how reinstatement is associated with different memory judgments, particularly those accompanied by recollection versus a feeling of familiarity (when recollection is absent). Classifiers were trained to distinguish between brain activity patterns associated with different encoding tasks and were subsequently applied to recognition-related fMRI data to determine the degree to which patterns were reinstated. Reinstatement was evident during both recollection- and familiarity-based judgments, providing clear evidence that reinstatement is not sufficient for eliciting a recollective experience. The findings are interpreted as support for a continuous, recollection-related neural signal that has been central to recent debate over the nature of recognition memory processes.”
4. ^ ^ Oscillatory Reinstatement Enhances Declarative Memory - Javadi, Glen, Halkiopoulos, Schulz and Spiers 2017
   doi: 10.1523/JNEUROSCI.0265-17.2017 downloadable here or see GoogleScholar.
   This research reported in this paper shows that memory recall is better if an alternating current of a specific frequency is applied to the brain at the time of a memory being encoded as well at the later time of attempted retrieval; it is not better if a different frequency is used at the time of encoding from the time of retrieval (the timescale between encoding and retrieval is quite short). This is a rather circuitous way of showing that similar pathways are used, but there is also a useful review of earlier research which has shown that reinstatement involves activation of the same neurons that were activated when the memory was encoded.
   First page, end of “Significance Statement” box: “reinstatement of neural oscillations during retrieval supports successful memory retrieval.”
   Page 9942, second paragraph: “Numerous models have argued that the successful retrieval of past experience involves a reinstatement of activity that previously occurred during encoding.”
5. ^ ^ Ibid. Oscillatory Reinstatement Enhances Declarative Memory
   Page 9939 (Introduction): “We now report causal evidence in support of the oscillatory reinstatement hypothesis. We took advantage of the potential capacity of transcranial alternating current stimulation (tACS) to entrain oscillations. Gamma and theta oscillations have been shown to have a mechanistic role in memory formation, linking memory formation to cellular mechanisms of learning, and coordination of hippocampus with other brain areas.”
   Page 9942 (Discussion): “In this view, the stimulation enhances memory by reinstating the encoding conditions in the network of brain areas responsible for the reactivation of the memory trace. This reinstatement may enhance processes such as pattern completion where similar network level inputs are transmitted to regions reconstructing the pattern of activity laid down at encoding, such as is thought to occur in hippocampal area CA3.”
6. ^ ^ Time-locked multiregional retroactivation: a systems-level proposal for the neural substrates of recall and recognition - Damasio 1989
   doi: 10.1016/0010-0277(89)90005-X downloadable here or see GoogleScholar.
   Page 26, Introduction: “...during free recall or recall generated by perception in a recognition task, the multiple region activity necessary for experience occurs near the sensory portals and motor output sites of the system... Hence the term retroactivation to indicate that recall of experiences depends on reactivation close to input and output sites rather than away from them.”
7. ^ Reactivation of encoding-related brain activity during memory retrieval - Nyberg, Habib, McIntosh and Tulving 2000
   doi: 10.1073/pnas.97.20.11120 downloadable here or see GoogleScholar.
   This paper refers to “redintegration”, a term used in psychology to mean the recollection of a multi-sensory experience triggered by a single-sense event or thought.
   Page 11123, first paragraph of Discussion:
   “...these findings provide support for the view that retrieval of specific event information is associated with reactivation of some of the regions that were involved during encoding of this information.”
   Later in Discussion, last paragraph of left-hand column:
   “...sensory aspects of multisensory event information are stored in some of the brain regions that were activated at encoding.”
   Page 11124, last paragraph of Discussion:
   “...although we have stressed encoding-retrieval similarities in the present study and provided support that reactivation of encoding-related activity during retrieval refers to a real physiological process in the brain, it is important to stress that the reality of reactivation does not mean that retrieval is, or is no more than, a simple 'replay' of the activation in the same neuronal networks that are engaged at encoding. Rather, there is substantial evidence that episodic memory encoding and retrieval processes have different neuroanatomical correlates, and the present results may best be seen as providing an example where encoding and retrieval processes meet in the brain.”
8. ^ Conceptual representations in mind and brain: Theoretical developments, current evidence and future directions - Kiefer and Pulvermuller 2011
   doi: 10.1016/j.cortex.2011.04.006 downloadable here or see GoogleScholar.
   Abstract on first page, just over half-way through: “...concepts are flexible, distributed representations comprised of modality-specific conceptual features. Conceptual features are stored in distinct sensory and motor brain areas depending on specific sensory and motor experiences during concept acquisition.”
   Page 821, Conclusions, second sentence: “Convergent results indicate that concepts are flexible mental entities that are constituted by distributed represented conceptual features. Concepts are embodied in the sense that their conceptual features are represented in sensory and motor brain areas in an experience-dependent fashion.”
   Bottom of same page: “...the embodiment theory grounds abstract concepts in perception, action and emotion through their reference to concrete situations that can be experienced”
9. ^ ^ How emotions are made - The secret life of the brain - Lisa Feldman Barrett 2017 Pan Books (UK) or see GoogleScholar.
   This book, as the title suggests, is mostly about the construction of emotions, but it touches on many other areas, and does discuss the representation of concepts in the brain, because emotions are examples of concepts (see feeling and emotion).
   Page 26, in chapter 2 entitled “Emotions are constructed”, fifth paragraph, having discussed the construction of images in the brain, once the meaning is known: “This little magic trick of the brain is so common and normal that psychologists discovered it time and time again before they understood how it worked. We call it simulation. It means that your brain changed the firing of its own sensory neurons in the absence of incoming sensory input. Simulation can be visual... or involve any other senses. Ever have a song playing in your head that you can’t get rid of? That audio hallucination is also a simulation.”
   Page 373, note 1 relating to the same paragraph in chapter 2: “As is typical in science, different psychologists have called this mental feat by different names, depending on their research interests. Examples are 'perceptual inference' and 'perceptual completion', 'embodied cognition' and 'grounded cognition'.”
   And in online notes that accompany the book, first paragraph, relating to research that found that simply asking a volunteer to pull a face resembling an emotion created changes in the brain and the body that typically were found in real occurrences of that emotion: “Neurons in certain parts of the brain change the firing of neurons in sensory and motor regions of the brain. This process, known as simulation, is also called embodiment, embodied cognition, perceptual inference, or grounded cognition.”
10. ^ Grounded Cognition - Barsalou 2008
    doi: 10.1146/annurev.psych.59.103006.093639 downloadable here or see GoogleScholar.
    From page 617, abstract: “...grounded cognition proposes that modal simulations, bodily states, and situated action underlie cognition.”
    Page 618, third paragraph: “Simulation is the reenactment of perceptual, motor, and introspective states acquired during experience with the world, body, and mind. As an experience occurs (e.g., easing into a chair), the brain captures states across the modalities and integrates them with a multimodal representation stored in memory (e.g., how a chair looks and feels, the action of sitting, introspections of comfort and relaxation). Later, when knowledge is needed to represent a category (e.g., chair), multimodal representations captured during experiences with its instances are reactivated to simulate how the brain represented perception, action, and introspection associated with it.”
11. ^ Situated simulation in the human conceptual system - Barsalou 2003
    doi: 10.1080/01690960344000026 downloadable here or see GoogleScholar.
    Summary on the first page: “... conceptual representations are multi-modal simulations distributed across modality-specific systems.”
    Page 514, second paragraph: “Each time a component [of experience] is attended to, the information extracted becomes integrated with past information about the same component in memory. When attention focuses on a blue patch of colour, for example, the information extracted is stored with previous memories of blue, thereby producing categorical knowledge for this component.”
12. ^ Reinstatement of memory representations for lifelike events over the course of a week - Oedekoven, Keidel, Berens and Bird 2017
    doi:10.1038/s41598-017-13938-4 downloadable here or see GoogleScholar.
    This research uses MRI scanning to test retrieval of an episodic memory from a week previous and shows that the reinstatement does involve the same neurons, as did a number of previous studies that are cited.
    It also showed that memories are strengthened if the memory is “rehearsed” [any student knows that they remember something better if they go through it in their mind].
13. ^ Ibid. Reinstatement of memory representations for lifelike events over the course of a week
    Pages 1-2 (introduction) says that: “Reinstatement effects between encoding and retrieving episodic memories are usually seen within a 'core retrieval network' including the hippocampus/parahippocampal gyrus, the angular gyrus (AG) and posterior midline cortex (PMC) including precuneus and posterior cingulate cortex (PCC)”.
    Page 10 (discussion) says: “Reinstatement effects were localized within the core retrieval network. The effects were centered on posterior brain regions, namely bilateral precuneus, bilateral inferior lateral parietal lobe/angular gyrus and bilateral middle temporal/occipital gyrus. This network has been found in many memory retrieval studies... It is thought that these regions represent high-level, relatively abstract information, such as the situational content of an event, rather than low-level sensory information.”
14. ^ Abstract and concrete concepts have structurally different representational frameworks - Crutch and Warrington 2005
    doi:10.1093/brain/awh349 downloadable here or see GoogleScholar.
    Page 1, Summary, second column: “abstract concepts, but not concrete concepts, are represented in an associative neural network.”
15. ^ The Challenge of Abstract Concepts - Borghi, Binkofski, Castelfranchi, Cimatti, Scorolli and Tummolini 2017
    doi: 10.1037/bul0000089 downloadable here or see GoogleScholar.
    Abstract, page 1: “The way in which abstract concepts are represented has recently become a topic of intense debate, especially because of the spread of the embodied approach to cognition. ... the most promising approach is given by multiple representation views that combine an embodied perspective with the recognition of the importance of linguistic and social experience.”
16. ^ Godel, Escher, Bach - Douglas Hofstadter Penguin Books UK 1979
    This fascinating book, despite its title, is mostly about the functioning of the brain, although it covers many other subjects as well.
    Page 50: “The perception of an isomorphism between two known structures is a significant advance in knowledge - and I claim that it is such perceptions of isomorphism which create meanings in the minds of people.”
17. ^ Ibid. Godel, Escher, Bach
    Page 710: “...the subjective feeling of redness comes from the vortex of self-perception in the brain”.

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