22/12/2011 by admin.

What determines how much short-term memory can hold? ScienceDaily has an item on this (here). The paper is by J.Kaminski etal., Beta band oscillations engagement in human alertness process, in International Journal of Psychophysiology.

A human being can consciously process from five to nine pieces of information simultaneously. During processing these pieces of information remain in the short-term memory. In 1995 researchers from Brandeis University in Waltham suggested that the capacity of short-term memory could depend on two bands of brain’s electric activity: theta and gamma waves. However, only now, through carefully designed experiments conducted at the Nencki Experimental Biology Institute of the Polish Academy of Sciences (Nencki Institute) in Warsaw, it was possible to unambiguously prove that such a relationship really exists…The hypothesis formulated by Lisman and Idiart in 1995 assumes that we are able to memorise as many ‘bites’ of information, as there are gamma cycles for one theta cycle. Research to date provided only indirect support for this hypothesis…Only based on discovered correlations the ratio of the length of theta wave to gamma wave was determined and the likely capacity of verbal short-term memory was determined…Following the EEG recording, the volunteers, were subjected to classic short-term memory capacity test…(They) observed that the longer the theta cycles, the more information ‘bites’ the subject was able to remember; the longer the gamma cycle, the less the subject remembered… correlation turned out to be very high and it confirmed the hypothesis of Lisman and Idiart.

So we can manipulate as many of ‘bits’ of information in short-term memory as we can fit beta waves into a single theta wave. Each ‘bit’ would be carried by a beta wave.

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16/11/2011 by admin.

People have noted often that we are conscious of our memory recall from episodic and semantic memory and also of imaginings. That is what it means to recall or to imagine – to be aware of the memory or the imagining. It is as if conscious awareness was a structure into which our awareness of ‘now’ or of some memory of past time or even some imagining of future or fictitious time, can be housed. It has been likened to a work space, a theatre, a model world – for now I am going to call it the conscious awareness structure. It is a 3D space centered on ‘here’, ‘now’ and ‘I’ but with the ‘here’, ‘now’ and occasionally the ‘I’ being ‘virtual’ when dealing with recalled memories or imaginings. We seem to be able to tell the difference between our awareness of the three different sources of the experience. It is not that the mechanics of recall or imagining are conscious but that the awareness of the result is in our conscious experience. I suspect that the same structure is used to house dreams.

It may be (and appears to me likely) that the process of recall is not a simple one. When I try to remember events from long ago, I find that they now incorporate changes or additions that make them fit with my current view of the world. I remember the pinkness of a particular dawn and it is placed in a particular farm yard. It is a familiar image from being recalled many times. Then I run across a photograph of the yard in question and I am surprised that my memory is physically impossible – there is no place in that yard to see the perspective I remember. Now when I recall the dawn it is seen corrected from its previous deviation. When we recall, we must fit the memory into our current conscious awareness structure. Throughout our lives, our bank of memories is reworked, consolidated, updated and so on to keep the bank useful and consistent. Some may think this is a poor way to arranged things. It would be better if evolution had produced an indelible, accurate trace of our past. But the purpose of our memories is not accuracy or permanence; it is usefulness because memory gives the elements used to think, solve problems, learn, plan the future, invent, avoid disaster. If I buy a new stove, I still want to use the lessons I learned on my old stove, not re-learn cooking with each change in my kitchen. Old memories have to be made to fit in the current structure of our awareness or they become useless. Little and large bits of memory are part of the stuff of thought.

We may (and again it appears to me likely) use fragments of memory to create imaginings. Stripped of their reference to a particular event, fragments can be furnish the pieces of an image – a tree here and a park bench there. Tulving’s notions of mental time travel and the possible connection of amnesia and inability to imagine are pointers to this sort of use of memory for imagining. These fragments used to form imaginings do not effect the original memory though, because the context of the original memory has to be part of the reworking that can occur with memory recall.

How important is the link between memory and consciousness? David Chalmers postulates the idea of a type of zombie that is indistinguishable from a conscious person but lacks consciousness. He says because we can envisage such zombies, they must be logically possible and therefore….well, many things follow. But it does not seem to me that his idea of zombies can be envisaged. People without consciousness would be very distinguishable from those without. A person without consciousness is likely to have no memory or a very poor one and no imagination or a very poor one. They would be very poor learners and speakers. The fluid easy flow of elements between consciousness and memory is extremely important to how the brain works. The conscious awareness structure is a very important component of the brain. It is well worth its cost in biological terms.

In the next post in the series, I am going to leave the memory connection and deal with other possible functions of consciousness. The reason for examining memory first is that I think it is neglected in discussions of consciousness.

There is more to come. Previous posts in this series:

Possible functions of consciousness 1 - leading edge of memory

Possible functions of consciousness 2 – gate to meaning

Possible functions of consciousness 3 – working memory

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04/11/2011 by admin.

As well as the episodic and semantic types of explicit memory featured in the first two parts of this series (and the implicit or procedural memory which seems to have no connection with consciousness), there is another important type of memory – working memory. How working memory actually works is far from a settled question. It may not be one thing – but several separate working memories. The working memory that I am discussing has these characteristics: it has limited capacity of 7 or less items in memory; it holds those items for a limited time, about a second unless replaced by new items; items being held can be manipulated; the items appear to be in consciousness or extremely easily brought to consciousness; they seem to be the focus of attention or extremely easily made so. This is the working memory that is needed for intelligence and correlates with IQ. It is needed for certain types of accurate detailed calculations and similar cognition. It is needed for creating and interpreting complex sentences. It is required for keeping concentration on a task and some other executive functions. Most descriptions of consciousness include working memory as well as a larger less detailed world view (a global ‘gist’) and attention. Avoiding problems with exactly how both consciousness and working memory are defined and bounded, whether one is a part of the other or they are separate mechanisms – let us just consider them as inseparable under normal conditions.

Daniel Kahneman introduced the terminology of System 1 thinking and System 2 thinking. System 1 is unconscious, automatic, very fast while System 2 is conscious, does orderly reasoning, and is very slow. I think that all actual cognition is like System 1, and System 2 only differs by passing through consciousness.

More and more it appears that cognition is primarily an unconscious activity. We are aware of only a very tiny proportion of the cognition our brains do. And even for that tiny proportion we are not aware of the actual cognition but only of the changes it makes in the items held in working memory. If I add 5 to 17, I am aware of: task is to add 5 to 17, add 5 to 7, that is 12, but it is 17 not 7 so add 10 to 12, answer 22. But I have no awareness of how these steps are done – my awareness just jumps from one step to the next. Even given that the cognition itself is not a function of consciousness – we still seem to require consciousness to feed and hold items in working memory so that they can be manipulated. Tasks that are not sequential are difficult to do using working memory and tasks that are sequential are difficult without working memory. When working memory is used, the changes in what is held in the working memory are registered in consciousness.

Working memory (and therefore consciousness) is involved in doing mental arithmetic because we need the explicit semantic memory to retrieve facts like ‘5 plus 7 equals 12′ which we have been taught by rote as small children. The same is true of mental logic, games with rules like bridge or chess, where much of the reasoning is sequential and tends to need explicit memory.

Sentences can be understood or created in a way that seems effortless but it does require a certain amount of juggling – holding this word until it is clear which meaning I should understand by it or which ending is grammatical for it and so on. The words and idiomatic phrases are in semantic memory to be retrieved as needed. Much of the juggling is unconsciously done but the results are past through consciousness for all those cases where working memory is involved.

We need working memory to learn motor skills. Once learned they can be done without working memory or even consciousness. But when learning such motor skills sequence and timing are important and it seems that learning the rough motor idea of a sequence takes the sort of manipulation that can be done on items held in working memory. Once the rough motor program is there, it can be honed and smoothed without consciousness or working memory. Soon there is a high skill level that is disrupted by conscious thought. Golfers must not think about the mechanics of their swing consciously or they will lose their skill.

There is no reason to think of this use of working memory as ‘the conscious mind’. The word ‘mind’ implies a system of cognition; and ‘conscious mind’ implies a system of cognition that is separate from unconscious cognition. However, all the manipulation, all the cognition is not part of awareness. We are not aware of how it is done. We are not aware of how 5 is found a retrieved from memory. It just pops in. All we are aware of is the flow of events, the stream of consciousness. In is more reasonable to think of having one undivided mind which does the work of cognition and a small part of the results rise to consciousness and so we are aware of them – one pop at a time.

So again we come to the function of consciousness. It is involved in a particular type of thinking in that it holds the keys to working memory. This type of thinking is very important to language, mathematics and logic. This function alone would be worth its cost.

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29/10/2011 by admin.

This is the second post in a series. The first post dealt with the importance of ‘experience’ in the sense of episodic memory, with consciousness supplying the moments making up an episode. Events that we are not conscious of simply do not get stored in episodic memory.

There is another type of memory which is not episodic, not autobiographical, carries no time and place information. It is usually called the semantic memory although it is not just about language. It stores facts, the sort of facts that you can state in natural language or some other representation (equations, musical scores, diagrams etc.). These are time-less, place-less, agent-less bits of understanding. This is memory of meanings, understandings, relationships, knowledge, ideas, concepts, and words with minimal context. The storage and retrieval processes of episodic and semantic memory appear to be separate with the exception that they are both declarative, or explicit, memory systems and therefore storage is from consciousness and retrieval is into consciousness.

What is the meaning of a word? Well, a word by itself does not have meaning. Meaning is gained by the relationships between words – they are defined in terms of other words/concepts.

Meaning is gained by how an entity takes part in the model of reality that we produce, by how it relates to other entities in the model. This model is what consciousness is derived from. Consciousness, in effect, brings the meaning from the model to the semantic memory and consciousness holds the meaning when it is retrieved from memory.

It is not clear whether semantic memory is stored as networks, matrices, hierarchies, chunks or some other embodiment. Whatever the structure, it supplies us with categories, contrasts, generalizations, and metaphoric analogs. Probably this structure is shared with other mammals, perhaps other vertebrates, but language has made it a powerful tool for humans by storing words so that they are retrievable into consciousness in ways that fit with our world model.

Language and other meaning systems are so important to us in communication with others and even within ourselves – their value cannot be overstated. The function of consciousness as a gateway to semantic memory is worth a great deal of biological cost.

In the three and a half years that I have been closely following scientific ideas about consciousness on the web, I have encountered a number of excellent ways to look at/ models of/ theories about consciousness. But I have not encountered anyone make a case for an intimate link between consciousness and declarative memory (except for the obvious definition of ‘declarative’ and ‘explicit’). I am surprised at this lack because the link seems so important in my view. If any readers know of such a argument having been made, I would appreciate a link to it.

There is more to come. The posts in this series to date:

Possible functions of consciousness 1 - leading edge of memory

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20/08/2011 by admin.

ScienceDaily reports (here) on a paper by Bindschaedler, Peter-Favre, Maeder, Hirsbrunner, Clarke in Cortex, Growing up with bilateral hippocampal atrophy: From childhood to teenage.

A child with damage to the hippocampus at birth did have some memory: memory of events was affected but not memory of general knowledge. His episodic memory was almost 90% gone while his semantic memory was within normal levels. This means that the two types of declarative memory (memory that can be accessed consciously) are different and that semantic memory is not just a consolidation of episodic memory.

The paper also seems to discuss evidence that recall and familiarity are separate.

Here is the abstract of the paper:

The respective roles of the medial temporal lobe (MTL) structures in memory are controversial. Some authors put forward a modular account according to which episodic memory and recollection-based processes are crucially dependent on the hippocampal formation whereas semantic acquisition and familiarity-based processes rely on the adjacent parahippocampal gyri. Others defend a unitary view.

We report the case of VJ, a boy with developmental amnesia of most likely perinatal onset diagnosed at the age of 8. Magnetic resonance imaging (MRI), including quantitative volumetric measurements of the hippocampal formation and of the entorhinal, perirhinal, and temporopolar cortices, showed severe, bilateral atrophy of the hippocampal formation, fornix and mammillary bodies; by contrast, the perirhinal cortex was within normal range and the entorhinal and temporopolar cortex remained within two standard deviations (SDs) from controls’ mean. We examined the development of his semantic knowledge from childhood to teenage as well as his recognition and cued recall memory abilities. On tasks tapping semantic memory, VJ increased his raw scores across years at the same rate as children from large standardisation samples, except for one task; he achieved average performance, consistent with his socio-educational background. He performed within normal range on 74% of recognition tests and achieved average to above average scores on 42% of them despite very severe impairment on 82% of episodic recall tasks. Both faces and landscapes-scenes gave rise to above average scores when tested with coloured stimuli. Cued recall, although impaired, was largely superior to free recall.

This case supports a modular account of the MTL with episodic, but not semantic memory depending on the hippocampal formation. Furthermore, the overall pattern of findings is consistent with evidence from both brain-damaged and neuroimaging studies indicating that recollection requires intact hippocampal formation and familiarity relies, at least partly, on the adjacent temporal lobe cortex.

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14/08/2011 by admin.

One of the interesting things about the Madl, Baars, Franklin LIDA model is the number of memory stores that it envisages. I have thought of consciousness as the ‘leading edge of memory’, at least of episodic memory. Hence my interest in the model’s use of memory.

Let us walk through their cognitive cycle to see what forms of memory are mentioned.

In the perception part of the cycle, the percept is held in the preconscious buffers of LIDAs working memory (workspace) and temporary structures are built. I assume the temporary structures are a preliminary world model. This seems definitely wider than the local sensory memories like visual memory.

The residual contents of the working memory is associated with the incoming percept and with associations from episodic and declarative memory in order to create an updated working memory. In summary, a number of memory stores are associated to give the current workspace: the new percept, the previous workspace, episodic memory, declarative memory. But they do not include and input from a motor system memory.

This resulting workspace is examined by attention processes to bring some parts of the workspace into consciousness. These parts (the novel, relevant, urgent and insistent) are transferred to another memory, the global workspace. This is equivalent to conscious broadcast as the contents of the global workspace are available to many process in the brain.

A procedural memory is postulated, hold various relevant behavior schemes which can retrieve the information they require from the global workspace. Goals are adjusted, actions selected and taken. Results of the action are fed back into the cycle through effects on the environment being included in sensory input.

In summary and in different words we have: individual stores in each sensory mode, a store with the preliminary precept, a store for finished world model, stores for episodic/declarative long-term memory, a store for ongoing behavior plans/goals, a store of action implementation procedures. This model gives a look at the sort of memory stores that are likely to be needed for cognition.

I have a big reservation about this cycle (although in general it is attractive), it does not deal well with prediction. For improvement, if we start with an action procedure rather than incoming sensory information and draw the cycle from that starting point. The action procedure, as well as, and before, producing the action, also is integrated into the existing workspace so as to create a model of the world as it is expected in a fraction of a second. What fraction of a second? Long enough for the conscious broadcast of the global workspace to coincide with the prediction - so that ‘now’ is ‘now’. The incoming sensory information can be compared with the workspace to register any errors and allow the action procedure to be amended if required. In other words, sensory and motor systems have two links: there is an external link through the environment and an internal one through prediction and they are compared in the workspace.

Madl, T., Baars, B., & Franklin, S. (2011). The Timing of the Cognitive Cycle PLoS ONE, 6 (4) DOI: 10.1371/journal.pone.0014803

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19/04/2011 by admin.

In change blindness some part of a scene is changed and the change is not noticed by the observer. This can happen when the change is not happening on the retina in a stable condition. It can happen when there is a mask (a blank screen to fast to see), a blink, an eye movement, a change in point of view, an interruption in a action and so on, anything disrupts the continuity of the retina image.

There was some questions of whether change blindness could happen with objects that were at the center of attention. Surely, if you were engaged in a conversation with someone, they could not be replaced with another person without the change being noticed. But they can as Simons and Levin showed in their paper (see citation).

What does this say about our memories? Simon and Levin say:

If we constantly noticed such changes, they would likely detract from our ability to focus on other, more important aspects of our visual world. Change detection as a method relies on the tendency of our visual system to assume an unchanging world. The fact that we do not expect one person to be replaced by another during an interaction may contribute to our inability to detect such changes. … Taken together, these experiments show that even substantial changes to the objects with which we are directly interacting will often go unnoticed. Our visual system does not automatically compare the features of a visual scene from one instant to the next in order to form a continuous representation; we do not form a detailed visual representation of our world. Instead, our abstract expectations about a situation allow us to focus on a small subset of the available information that we can use to check for consistency from one instant to the next.

In effect we delude ourselves as to the completeness of our immediate memory. We remember the unexpected if we notice but there is no guarantee that we will notice.

Simons D.J., & Levin D.T. (1998). Failure to detect changes to people during a real-world interaction Psychonomic Bulletin and Review, 5, 644-649

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27/09/2010 by admin.

Some people are surprised, even disturbed, by the idea that our vision does not give us an accurate picture of what we look at. For example, the colours we experience are not a measure of the wavelength of the light entering our eyes. But accuracy is not the point of vision; the function is to be useful and colour consistency is far more useful then fidelity to wavelength spectra. The same surprise is shown in the reaction to the idea that our memories are reworked continuously so that over time they lose their accuracy. This is not a fault in memory. Again the reason we store memories is to have a useful resource, not necessarily one with detailed accuracy. A great deal of biological energy is used to create memories and to re-consolidate them and therefore we can assume that they have a very important biological role.

In order to have episodic memory, we first have to have the experiences to remember – we create consciousness experiences which become stored as temporary memories. These are soon made more permanent as an event or an episode. Over weeks, months, years, decades they are continually reworked and re-consolidated. They are packaged together and lose their individuality, they are up-dated by newer memories, they are categorized and lose detail not related to their category. Eventually they lose their character as episodic memory and became more a factual or semantic type of memory. What has happened in all this change is that we have learned from experience. This in itself would probably justify the biological cost of consciousness and memory but more has been proposed by Moshe Bar, Donna Rose Addis, Daniel L. Schacter and others. They have put memory at the center not just of the past and learning but of the present and future, of prediction, understanding and cognition.

Bar envisages a ‘proactive brain’ which builds analogues by examining what something is like. If A is like B then they share an analogy which grows as other like things are remembered. Each memory added to a particular analogy brings associations with it, so the associations of each analogy grows. The associations of an analogy are in effect predictions of what else will be found along with the analogy. Thus memory is the material of prediction and foresight. Between memories, predictions and idle imaginings we have the simulations we need to plan our actions. These simulations can even become ’scripts’ for guiding behaviour and sets of scripts to determine a ‘mindset’ appropriate for a particular type of situation.

Schacter and Addis call their scheme the ‘prospective brain’.

A rapidly growing number of recent studies show the imagining the future depends on much of the same neural machinery that is needed for remembering the past. These findings have led to the concept of the prospective brain; an idea that a critical function of the brain is to use stored information to imagine, simulate and predict possible future events. We suggest that processes such as memory can be productively re-conceptualized in light of this idea.

In fMRI studies of subjects remembering and imagining events, they have identified what they call the ‘core brain system’ which integrates information from past experiences about relationships and associations and uses the information to construct mental simulations. There is a large overlap between the areas of the brain involved in elaborating past and future events. Further there is a large overlap with the default network we use for day-dreaming.

The cognitive machinery outlined by this line of research would convincingly be worth its biological cost by giving us effective and appropriate behaviour. Memory may not be entirely accurate but it is wonderfully useful.

ADDIS, D., WONG, A., & SCHACTER, D. (2007). Remembering the past and imagining the future: Common and distinct neural substrates during event construction and elaboration Neuropsychologia, 45 (7), 1363-1377 DOI: 10.1016/j.neuropsychologia.2006.10.016
Schacter DL, Addis DR, & Buckner RL (2007). Remembering the past to imagine the future: the prospective brain. Nature reviews. Neuroscience, 8 (9), 657-61 PMID: 17700624
Bar, M. (2009). The proactive brain: memory for predictions Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1521), 1235-1243 DOI: 10.1098/rstb.2008.0310

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09/09/2010 by admin.

According to Victor Lamme, the reason that the study of consciousness is so difficult is that it gives priority to introspection and behaviour so, as a result, we are fooled into thinking that we know what we are conscious of. By adding evidence from neuroscience into the mix, he hopes to understand consciousness. He looks at the components of what we call consciousness and teases them apart: the phenomenal experience, the behavioural control, the access to the experience/ability to report it, the working memory, the attention focus. Then he asks what neural events match which aspects of consciousness.

Vision is the sense that Lamme uses to explain his model. The first cut is made between the iconic memory and working memory. The iconic image has more detail, is short-lived and overwritten by a change of scene, is not useful to cognition; while the working memory image has limited detail, can last for some time and is not overwritten by new events, is useful to cognition. The parts of the iconic image that become part of the working memory are those few which are attended to – so this cut can also be seen as consciousness with attention verses consciousness without attention.

Consciousness is then divided into stages using the neural events associated with consciousness. These events are the fast feedforward sweep (FFS) and the recurrent processing (RP). In the FFS, information flows from the visual cortex forward through the dorsal and ventral paths to the motor and frontal cortex area. This sweep starts with purely visual processing and ends with motor and executive processing. In RP, information flows out horizontally in each area and flows back to lower levels, as far back as the original visual cortex. In other words, there is a bottom-up stream followed by a sidewise and top-down spread.

Lamme’s stages are:

Stage 1 – Superficial processing during the FFS. Processing stops at the visual areas if a stimulus is not attended to and is also quickly overwritten by a masking image.

Stage 2 – Deep processing during the FFS. If stimulus is attended to but is quickly overwritten the result is that processing reaches the prefrontal and motor areas but remains unconscious.

Stage 3 – Superficial processing with RP. If the stimulus is not masked and has time to evoke RP but is not attended to or is neglected (inattentional blindness, change blindness, attentional blink), the FFS does not travel far but is followed by RP in the area it has managed to reach.

Stage 4 – Deep or widespread RP. If the stimulus has time for the FFS to travel fully forward and is attended to, the RP will span all levels from original visual to executive areas. This consciousness can be reported.

With this four stage model, Lamme labels Stages 1 & 2 as not having consciousness, Stage 3 as iconic representation and Stage 4 as working memory representation. The travel of the FFS forward is associated with attention and the spread of RP is associated with phenomenality.

Lamme argues that the inclusion of neuroscientific evidence is important.

“My main objection is against a form of cognitive psychology where mental constructs are taken as undeniable truths to which neuroscience has to be fitted. I would argue that in the study of consciousness, there are no undeniable truths.

That is the standard approach in science. Intuition told us the sun revolves around the earth, while in fact it is the other way around. Intuition dictated creation, where evolution is the counterintuitive scientific answer. To make scientific headway in our science of consciousness, we need to acknowledge that our intuitions may be wrong and need to be set aside. The upshot is that – finally – we may start solving the questions that have been bothering us for the ages.”

What a breathe of fresh air to have introspection taken off its pedestal!

I have my own list of what explanations of consciousness should address and Lamme touches most of them. My disappointment is the sparse mentions of the role of the thalamus and the nature of synchronous activity as well as the lack of a mention of the apparent projection into the near future of the representation of moving objects.

 
Lamme, V. (2010). How neuroscience will change our view on consciousness Cognitive Neuroscience, 1 (3), 204-220 DOI: 10.1080/17588921003731586

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29/07/2010 by admin.

Memories move through stages when they are formed: they are ‘encoded’ or some other process of being prepared (perhaps working memory), they are held in an early stage (short term memory), changes occur in synapses in both the hippocampus and cortex forming a somewhat stable memory from minutes to hours later (synaptic consolidation), the memories are processed so that they are less dependent on hippocampus and more on the cortex from days to years after (system consolidation). Consolidated memories are fairly stable – but- when they are recalled into consciousness, they can be modified. This seems to be the main way in which memories are re-consolidated (or changed) over time. Passing a memory through consciousness means it is re-stored, either unchanged or updated depending on circumstances. Much of sleep is busy with the consolidation and re-consolidation of memories. This is a simplified outline of the current science on memory and it is important to realize that more is unknown than known.

An interesting item in BPS research digest (here) looks at experiments with a treatment for traumatic memories, EMDR, eye movement desensitization and reprocessing.

A controversial treatment for post-traumatic stress disorder involves the traumatised person holding a painful memory in mind while simultaneously following with their eyes the horizontal movements of their therapist’s finger… Raymond Gunter and Glen Bodner have tested three possible explanations…

(first) relative to staring straight ahead, eye-movements increased arousal levels. (undermining) the idea that eye movements activate an innate investigatory reflex that inhibits fear and provokes relaxation.

A second experiment showed that both horizontal and vertical eye movements reduced the vividness and emotionality of the students’ memories. (undermining) the idea that horizontal eye movements aid interhemispheric communication, thus allowing the more rational left hemisphere to process the right hemisphere’s traumatic memories.

(third) experiment showed that the students’ memories became less vivid and emotional, not only when they performed concurrent horizontal eye movements, but also if they instead performed a simultaneous simple hearing task. This undermines the idea that EMDR works specifically by taxing the so-called “visuo-spatial sketch-pad” of working memory. It suggests instead that the mechanism underlying EMDR is a more general effect based on taxing the big boss of short-term memory - the central executive.

…performing a concurrent task, be it eye movements or some other distraction, while also recalling a painful memory, allows a person to be exposed to that memory, without having the mental resources available to get too upset by it. Over time, this process acts like a form of gentle exposure to the memory, as the person learns that they can, after all, cope with their past.

This seems a clear case of a memory being forced to change during re-consolidation – by passing through consciousness under conditions that modify the memory.

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