Tuesday, June 05, 2007

The faculty of Imagination: Neural substrates and mechanisms

Imagination refers to holding in mind a representation that may not be (yet) 'true' and does not necessarily reflect the facts about the external world or the Reality as of now. The act of imagination may use previous memories and a general knowledge of the world to recreate past memories or to imagine novel future events.

An article by Simon Baron Cohen, discusses the biology of imagination. Simon distinguishes between the contents of imagination , which are culturally determined; and the capacity for imagination, which is biologically grounded. He also focuses on imagination as a false or distorted representation of Reality as opposed to mere imagery, which though itself also being a mental representation, may more-or-less represent the world accurately.

Imagery may be necessary for human imagination. It has been suggested that all the products of the imagination are derived from imagery, following some transformation of the basic imagery. For example, Rutgers’ psychologist Alan Leslie, when he worked in London in the 1980s, proposed that imagination essentially involves three steps: Take what he called a ‘primary’ representation (which, as we have already established, is an image that has truth relations to the outside world). Then make a copy of this primary representation (Leslie calls this copy a ‘second-order’ representation). Finally, one can then introduce some change to this second-order representation, playing with its truth relationships to the outside world without jeopardising the important truth relationships that the original, primary representation needs to preserve. For Leslie, when you use your imagination, you leave your primary representation untouched (for important evolutionary reasons that we will come onto), but once you have a photocopy of this (as it were), you can do pretty much anything you like with it.


Thus, what Leslie contends is that the faculty of imagination involves a mechanism for making a second -order representation in the mind of a past stimulus (the imagery), in the absence of the stimulus in the here and now. Crucially, the faculty of imagination also involves the ability to modify the stimulus in such a way so that it no longer represents the original stimuli accurately. One , either creatively or mundanely , transforms some aspects of the original stimulus. to come up with something imaginary (like the concept of a unicorn). Thus, it seems there are three faculties involved- one for maintaining a second order representation of an object in absence of stimulus, another for distorting or manipulating that representation to come up with novel objects and the last for keeping this novel representation as different from the original representation to avoid confusion and loss with reality.

Leslie calls the abilities to form second-order representations and the ability to change or distort these representations as Meta-representation capacity and links this to the ability to indulge in pretend play in 9-15 months old infants and the ability for mind reading or false-belief or Theory of Mind (ToM) ability in older children (4 yr olds). The contention is that pretend play enables one to keep two copies (one primary and the second a false second-order representation) of an external object in mind simultaneously while at the same time enabling one to know that one is true and the other false or a pretense. Also pretend play involves treating one object (say a banana ) as another object (say a telephone) and thus develops the capacity to distort the second order representation of an object. This meta-representation ability in turn is the pre-requisite for imagining future outcomes and thus for successful planning in older adults.

Before I continue, let me pause and define imagination faculty in more rigorous terms for forthcoming discussions. We would be primarily concerned with the ability to shift focus from now and here to then and there and also from self to others. We would be concerned with imagination as depicted in scenarios involving people or objects with agency. Also please refer to this document by Buckner and Carrol.

Thus, the following kinds of imaginations are under preview:

  1. Remembering the autobiographical past (reconstructing past memories or imagining what it felt like 'then' in the past vis-a-vis 'now').
  2. Simulating the autobiographical future or Prospecting (constructing plausible future scenrie that would happen 'then' as compared to 'now')
  3. Navigating (constructing a scene that is 'here' (first person perspective) to 'there' (third person perspective)) Changes in spatial perspective - seeing things/ scenes from someone else's point of view . Please keep in mind the distinction between two types of spatial point-of-view taking - one involving line tracing and the other perspective taking). It is my contention that while normal kids would rely more on perspective taking, the autistic children rely on line tracing for navigation.
  4. Theory Of Mind : (constructing a representation of 'another' as opposed to self) . Thus this too involves a shifting of focus from one agent to another with the concurrent risk that the new representation may not be true.

Note that all of the above involve or are about persons or entities with agencies and their beliefs/ memories / imaginations and how they are distinct from the actual reality. This is important as the neural evidence would pertain to only this class of imaginations and would not generalize to imagining events not involving agency, for example imagining a unicorn.

In what sense might a meta-representational capacity be essential for mind-reading? Let’s define mind-reading as the ability to put yourself in someone else’s shoes, to imagine the other person’s thoughts and feelings.iv Leslie’s deeply interesting argument is that when you mind-read, you again need to quarantine your primary representations. Here’s how his argument goes. Just as your mental picture of a fish has ‘truth relations’ to a real fish in the outside world, so a belief, or a sentence, has truth relations to real events in the outside world. Thus, ‘John is having an affair with his colleague’ is a primary representation of a state of affairs, and is true if John is indeed having an affair with his colleague. But when we mind-read, we again take the primary representation (step one), copy it so that it becomes a second-order representation (step two), and can then add a prefix (step three) that completely changes its truth relations with the outside world.

Thus, we can take the primary representation ‘John is having an affair with his colleague’ (step one). We can copy it to produce an identical version ‘John is having an affair with his colleague’, except this version is tagged as being a copy or a second-order representation (step two). Finally, we can add a prefix such as ‘Mary believes that’ to the second-order representation to end up with ‘Mary believes that “John is having an affair with his colleague” ’ (step three).

Such second-order representations have unique logical properties, an insight that Leslie borrowed from the standard views in philosophy of mind. They have, to use the jargon, referential opacity. ‘I pretend that “this tea-cup is hot” ’ is true if I pretend this, irrespective of whether the tea-cup really is hot. ‘Mary believes that “John is having an affair with his colleague” ’ is true if Mary believes it, irrespective of whether John really is having an affair. According to Leslie, and I think he is right, when we mind-read (just as when we use imagination), we employ such second-order representations. I can maintain my own knowledge base (John is not having an affair) whilst representing someone else’s different (possibly false) belief (Mary believes he is).


Thus, ToM has also been placed squarely in the category of tasks requiring Imagination, as we have defined it. Simon than contends that in Autism children lack this Imagination circuit or network and have deficts with ToM in particular and Imagination in general. Thus, as per this hypothesis they must also have problems imagining future autobiographical events, problems with episodic memory and problems with perspective taking approach to spatial navigation. All this still needs to be tested.

Let me now digress a little and point to data that suggests that the module we are talking about is specific to Imagination involving Agency and not for all second-order representations. When confronted with questions that do not require an agency , the autistic people perform as well on control tasks that require false representations in the mind.

To determine whether the poor performance of autistic children is due to a specific impairment in theory of mind, Leslie constructed a control task that very closely resembles the Sally-Ann task but does not rely on theory of mind. In the control task, the children watch an actor photograph a cat that is sitting on a chair. The cat then moves to a bed, and the subject is asked to predict what the photo will show. The control task is formally similar to the Sally-Ann task in that both tasks require children to infer the contents of a representation that does not reflect the current state of affairs. The photograph task and a standard FB task were given to normal 3 and 4-year-olds and mental-age-matched autistic adolescents. The autistic children performed slightly better than the normal 4-year-olds on the photograph task but worse than normal children on the standard FB task. The normal 3-year-olds failed both the FB task and the control task. The autistic children also outperformed normal children on another control task. In the second control task, the position of a cat was marked on a map. The cat then moved, and children were asked to predict the location of the mark on the map. The results indicate that autistic kids can meet the general problem solving demands of false belief tasks, but normally developing 3-year-olds cannot.

Leslie concludes that the three year olds have a difficulty with suppressing or inhibiting their own beliefs and desires (the primary representations) and selecting the second-order representations or beliefs of Sally. Thus his hypothesis is that their performance reflects a failure of inhibition or selection processing. this is clearly tied to the third ability we have identified of keeping two representations operate. They confuse between the two, and it is my contention that this is due to their inability to hold two representations of same objects in memory at the same time. Thus, three year olds also do not have episodic memory or the capacity to hold in memory the same object representations, but with different time coordinates.
Leslie also demonstrates that this deficit in inhibition, that is age dependent, is different from the deficit in Autistic children. I suspect the deficits in Autistic people are due to their propensity to view entities with agency too as objects and thus not having any beliefs , desires or emotions.

Now let me return to the Buckner and Carrol paper. It is an important paper that shows that we use the same brain areas for Remembering the past, imagining the future, ToM tasks and Navigation. Morover, the paper shows that this default network is nothing else but the default network in brain. It is to be remembered that the default network is the network active in absence of any stimulus and one feature of Agency dependent imagination we have seen earlier is that one should be able to form representations in absence of any stimuli. Also, we have already covered research that suggest that same brain areas are used for remembering the past and imagining the future.

Let me give you the abstract of the paper:

When thinking about the future or the upcoming actions of another person, we mentally project ourselves into that alternative situation. Accumulating data suggest that envisioning the future (prospection), remembering the past, conceiving the viewpoint of others (theory of mind) and possibly some forms of navigation reflect the workings of the same core brain network. These abilities emerge at a similar age and share a common functional anatomy that includes frontal and medial temporal systems that are traditionally associated with planning, episodic memory and default (passive) cognitive states. We speculate that these abilities, most often studied as distinct, rely on a common set of processes by which past experiences are used adaptively to imagine perspectives and events beyond those that emerge from the immediate environment.


I would request that the readers go back up a little and re-read the faculties required for imagination:


They involve second-order representation without stimulus (as in the activity in default network when no tasks are being carried. This spontaneous activity in the default network suggest that this is one region that can do its work without any input data.)
Distorting, changing , modifying the representation and moving them back and forth in time and space: I believe the frontal regions are involved in combining different stimuli, sequencing and planning them to archive novel combinations.
Keeping the false/ imagined/ other-people representations distinct from primary representations: I believe medial temporal lobe is crucial here. It is implicated in learning and memory and for keeping representations of past events (episodic memory). It thus has to keep the representations distinct, so that many memories may have the same constituent objects. Thus, the medial temporal lobe, I believe is mainly responsible for keeping the representations distinct.

It is interesting to note that the default network comprises of precisely these brain areas - the PFC and other frontal areas and the medial temporal lobe along with temporal-parietal junctions implicated in ToM. Also the fronto-polar region is implicated in the shifting of perspectives from self to other, from now to then etc and may be the most affected in Autism..

Functions that shift the perspective from the immediate environment to another vantage point create an interesting challenge for the brain. We must keep track of these shifts, otherwise our perceptions would blur together. Decety and Gre´zes note that ‘reality and imagination are not confused’. A computational model of how such a process might be structured is far from being defined, but it will probably require a form of regulation by which perception of the current world is suppressed while simulation of possible alternatives are constructed, followed by a return to perception of the present. Povinelli considered this issue from a developmental perspective and noted that coordination of internal perspectives ‘paves the way for the child to sustain not simply one current representation of the self but also to organize previous, current, and future representations under the temporally extended, metaconcept of ‘‘me’’’


The Fronto-polar regions are suspected behind this ability and I suspect are the most affected in Autism.

A final set of findings suggests that the frontopolar cortex contributes to theory of mind.

Thus Autism stems from the ToM deficts in the fronto-polar regions, plus the inability to keep many simultaneous representations in mind/'memory'. I would also suspect that same region is involved in agency attribution.

What does this selective generalization mean? The combined observations suggest that the core network that supports remembering, prospection, theory of mind and related tasks is not shared by all tasks that require complex problem solving or imagination. Rather, the network seems to be specialized for, and actively engaged by, mental acts that require the projection of oneself into another time, place or perspective. Prospection and related forms of self-projection might enable mental simulations that involve the interactions of people, who have intentions and autonomous mental states, by projecting our own mental states into different vantage points, in an analogous manner to how one projects oneself into the past and future.


In the end they very wisely conclude:

In this article, we have considered the speculative possibility that a core brain network supports multiple forms of self-projection. Thinking about the future, episodic remembering, conceiving the perspective of others (theory of mind) and navigation engage this network, which suggests that they share similar reliance on internal modes of cognition and on brain systems that enable perception of alternative vantage points. Perhaps these abilities, traditionally considered as distinct, are best understood as part of a larger class of function that enables flexible forms of self-projection. By this view, self-projection relies closely on memory systems because past experience serves as the foundation on which alternative perspectives and conceived futures are built.



That brings us to my final conclusion. I believe this is further evidence for the different cultures of Schizophrenia and Autism. If Autistic have a deficit with this ToM/ Agency default network, we also know that in schizophrenics too the default network works abnormally. I presume it acts unusually in the opposite way to that in Autism- attributing more agency, involving more imagination and self-projection.

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1 comment:

insidethegod said...

thank you for the informative read. . . memory and knowledge being different digits of the same hand, represented in neural oscillations, both form grip with the fingers of perception and attention to take hold of, manipulate, create, grasp, direct, strike asunder and unfold the imaggeneration of reality.

imagination, or the faculty of, is made up, and makes up every endeavor of our humanity.