11 . from sensation to cognition
Date: 1/27/2007
From: robert burgess
To: feldiescience
From Sensation to Cognition, Mesulam 1998,
Brain 121: 1031-1052
1. Introduction
2 From sensation to perception
2.1. The representation of visual experience
3. From perception to recognition: transmodal gateways
3.1. Mental imagery
3.2. Novelty-seeking
3.3. The valuation of sensation
4. Overview and speculations on the evolution of human consciousness
4.1 human consciousness
4.2 the biological purpose of perceptual and mnemonic abilities
This is a lengthy review article available free on-line at http://brain.oxfordjournals.org/cgi/content/abstract/121/6/1013.
I have summarized major parts of it below. The choice of heading included and the numbering system is my categorization of the paper. Italized text in qutations marks is taken directly from the text of the paper.
In this article Mesualm argues that the multi-level processing of sensation according to brain structure and function leads to human cognition and consciousness. It is not brain size that differentiates human behaviour from a frog but the synaptic distance from sensation to action.
Sensory processing in amphibians, reptiles and birds is "kept on a short leash". From sensation to action is of the order of only one or two synaptic levels. Whilst such a system is quick to respond it is also stereotyped and can lead to destructive behaviour.
"Examples cited:
- a turkey hen, whose protective maternal instincts dictate an attack on any moving object that fails to utter the characteristic peep of her chicks, will peck her own newly hatched progeny to death if she is made deaf; - rats with crossed sensory nerves in the hind limbs, one of which is inflamed, will hop on three legs to protect the healthy rather than the sore foot."
One of the major arguments for human consciousness and behavioural flexibility is the occurrence of novelty in more complex nervous systems:
"And an intrinsic bias emerges to pursue novelty and flexibility rather than sameness and stereotypy. The emergence of behavioural flexibility in mammals can be attributed to an expansion of the synaptic bridge that links sensation to action and recognition".
Mesulam describes the intermediate levels in the processing of sensation as the source cognition.
"The neural systems that bridge the gap between sensation and action provide the substrates for 'intermediary' or 'integrative' processing. The behavioural outcome of intermediary processing is known as 'cognition', and includes the diverse manifestations of memory, emotion, attention, language, thought and consciousness."
And
"The neurons that support intermediary processing are located predominantly within the 'association' and 'limbic' areas of the cerebral cortex".
"In addition to retinotopic location, its neurons are sensitive to orientation, movement, binocular disparity, length, spatial frequency, wavelength and luminance".
I include this line from the article to show just how complex a task vision is. Retinotopic refers to the fact that the way that light and images form on the retina is matched in the visual cortex. One way to imagine this is to think of the way that large computer cables are constructed. At one end of say 15 sockets is exactly matched at the other end by 15 pins. The wires running from one end the other match the wholes and pins throughout. Similarly, auditory mapping is tonotopic.
The figure (Figure 2 in the article) shown of 6 concentric circles illustrates Mesulam's hierarchical arrangement of the 6 levels of synapsing in the brain.
Each level of synapsing or "node" "is continually passing on information to the others rather than fulfilling its part of the processing and then transmitting a completed product to the next station".
Encoded in the first three synaptic levels are colour, form and motion. To speed up perception neurons at the fourth level are more strongly activated by faces than other objects ('f' in Fig. 2b).
Fig. 2 Each concentric ring represents a different synaptic level. Any two consecutive levels are separated by at least one unit of synaptic distance. Level 1 is occupied by the primary sensory cortex. Small empty circles represent macroscopic cortical areas or 'nodes', one to several centimetres in diameter. Nodes at the same synaptic level are reciprocally interconnected by the black arcs of the concentric rings. Coloured lines represent reciprocal monosynaptic connections from one synaptic level to another. (a) Visual pathways as demonstrated by experimental neuroanatomical methods in the macaque brain. (b) The inferred organization of the homologous visual pathways in the human brain. (c) Visual (green) and auditory (blue) pathways in the human brain. (d) Visual (green), auditory (blue) and transmodal (red) pathways in the human brain. In b, c and d, the anatomical details of individual pathways are inferred from experimental work in the monkey. The anatomical identity of many of the nodes is not specified because their exact anatomical location is not critical. This review is guided by the hypothesis that these types of anatomical interconnections and functionally specialized nodes exist in the human brain even though their exact location has not yet been determined.
"Transmodal areas" are defined as regions that have no one specific sensory input, they receive multi-sensory inputs from other unimodel regions that are reciprocal (i.e. connection and input to and from a region is returned).
Mesulam touches briefly on the Cartesian dualism debate- i.e. Descartes notion of convergence of sensation to the pineal gland. However, the question of "it all coming together" somewhere is carried out Mesulam says in "multiple theaters and where the actor and spectator are one and the same".
These transmodal areas include all heteromodal, paralimbic and limbic areas and occupy the fifth and sixth synaptic levels as shown in Fig. 2d.
"Mental imagery refers to the activation of sensory representations that are not part of ambient reality. It could be conceptualized as a special type of attentional process targeted to internal representations."
It has been shown that mental imagery activates the same neurons and neuronal circuits as when actually performed. Imagining spatial relations i.e. where objects are in space activates the occipito-parietal cortex whilst visualizing objects activates the occipito-temporal cortex. Hence other authors therefore describe two separate visual processing - the "where" and "what".
"Virtually any sphere of sensory processing could potentially become the target of mental imagery. Mental rotations and other reconfigurations of visual percepts could subserve nonverbal thinking, whereas the mental activation of auditory word-forms and related associations could support inner speech and verbal thinking."
I have always been fascinated in ATM and my own kinesthetic sense that for me it has an indelible connection with a visual image. I don't really differentiate between the two- kinematic and kinesthetic. Another topic for another time.
Here Mesulam presses the significance of sameness in perception as leading to stereotyped action- stimulus bound, bound by the stimulus or what Feldenkrais would call it compulsiveness.
"The bias for perceiving sameness and emitting automatic responses represents a 'default mode' of brain function and leads to behaviours that can also be designated as instinctual, stereotyped or stimulus-bound. One consequence of this organization is to enhance efficiency and reliability, but another is to promote premature closure, perseveration and response rigidity, phenomena frequently encountered in the behaviours of less evolved species, of infants and of braininjured humans."
Mesulam goes on to say that play is an antithesis of sameness. Play is not apparent in amphibians or reptiles (hence MacClean's line: " it is a lonely and empty life to be a reptile" see previous posting) but is present in birds and especially advanced mammals and of course primates.
"In humans, sensory deprivation and monotony induce restlessness and even vivid hallucinations."
Well we in the Feldenkrais Method have a lot to say about such things. Play as exploration leads to the detection of differences or novelties which is the basis for change and growth. This is basic to our method and later we'll see it basic as Mesulam concludes to the development of human civilization.
"Monkeys will work hard in a setting where the only reward is a peek through a window, and human subjects who are given a choice between familiar and simple versus novel and complex patterns, will consistently spend more time viewing the latter. The tendency for seeking novelty may even have survival value: in a prospective study of 2153 community-dwelling elderly subjects, those with a higher baseline level of 'curiosity' had a better chance to be alive and well 5 years later."
Curiosity may have killed the cat but it is one thing that keeps us alive and well. Again in reading this article I am struck but how much is similar to Feldenkrais teachings, not as Feldenkrais teachings or -isms but as our biological inheritance. We have evolved to be flexible, curious and novelty seeking in our behaviour.
"Emotion, mood and motivation modulate the neural impact of sensory events in a manner that reflects the subjective value of these events to the individual."
The amygdala has a role of giving a previously neutral event an emotional charge. Young monkeys don't fear snakes until learned from the mother. The amygdala is the organ that codes emotionally relevant events. Activate the amygdala and you get emotionally charged memories whilst lesions of the amygdala lead to hypo-emotion.
"Attention is difficult to define but easy to detect. It usually refers to an enhancement in the selectivity, intensity and duration of neuronal responses to events that have become emotionally and motivationally relevant."
"Thus, inferotemporal neurons show attentional enhancement to behaviourally relevant visual patterns, posterior parietal neurons to spatial targets, pyriform neurons to odorants, and Wernicke's area to words."
"Attention, emotion and motivation introduce a value system to sensory processing. These value-based modulations allow the CNS to sculpt sensory experience into a subjective landscape."
Attention brings along the whole brain, memory, attitudes to the thing being attended to. Hence one reason why in FM we maintain that merely the bringing of attention brings change. So during and after a body scan in a movement lesson we find ourselves already flatter on the floor.
The first synaptic level maps sensation retinotopically for vision and tonotopically for audition. The second synaptic level is more complex and involves colour and motion.
The third and fourth synaptic levels deal with things like as "faces, objects, words, and extrapersonal targets."
"The fifth and sixth synaptic levels contain transmodal gateways.. Transmodal nodes are critical for transforming perception into recognition, words into meaning, scenes and events into experiences, and spatial locations into targets for exploration."
"Since the nature, purpose and consequences of environmental events are relatively unpredictable, a new event is likely to activate all networks, at least initially. The steps of perceptual identification, deployment of spatial attention, naming, association with past experiences, assessment of present context, planning of options, inhibition of automatic responses and prediction of consequences proceed simultaneously and interactively. The process can be characterized as a rapid and iterative succession of mental scripts, scenarios and hypotheses that are triggered by interactions between environmental events and internal representations. The most relevant ensembles and networks gradually dominate the landscape of neural activity as they become more and more resonant with the goals and constraints of the prevailing context. The solution to the cognitive problem or task is defined as the settling of the entire system into a state of best fit. This is not the final product in a hierarchical assembly line, but a complex surface with many peaks and valleys, spread over much of the cerebral cortex."
Hence again novelty brings a difference and an activation of the entire brain. "Mental scripts" is a great description of the active nature of our sense of self and the world. We don't perceive without a history or knowledge and preconceived ways of responding. Inhibition here too a part of growth and learning like in FM.
The notion of best fit as the ultimate nature of processing sensation for action is interesting. It is similar to another version of the perception as a scientific process- we gather information, make a hypopthesis and then test it. Where the result is the best explanation for now it is adopted as a truth or theory of the world or self.
"From a strictly behavioural point of view, the existence of consciousness might be inferred when a living organism responds to environmental events in an adaptive way that is not entirely automatic. The path from sensation to cognition in the frog is straight and narrow, leading to an equally modest texture of consciousness. In the human brain, the multiple paths inserted between the first and sixth synaptic levels and the addition of working memory . greatly expands the horizon of consciousness by lengthening the temporal influence of internally or externally generated events and by increasing the number of processing channels that can be accommodated simultaneously. The impact of working memory on the quality of consciousness may resemble the impact of resonance, reverberation and dynamic range on the quality of the auditory experience in a concert hall."
What is working memory?- multiple streams of information is made accessible in a parallel fashion in the pre-frontal cortex i.e. multimodal rather than unimodal. Mesulam compares working memory to the amount of balls a juggler can keep in the air. So the intermediate processing levels and the multimodal working memory enhances the horizon and quality of consciousness. Again it sounds so familiar to FM work. Our experience with FM provides us with a greater horizon and quality to our consciousness. We need FM to return us to our evolutionary biological capacity.
Mesulam argues that the many dimensions of sensation created in the many pathways through the complex network of the intermediate synapses allows for mental relativism. The object in vision does not change when viewed from another angle or another time. This notion Mesulam extends to an act being condoned under one condition but not another. And that individual perspectives may lead to different interpretations and hence then an important feature of relativism is the ability assume another's perspective. Another ability encouraged by Feldenkrais.
"A tolerance for multiple alternative representations may provide the critical ingredient that sets the special flavour of human consciousness." (Just for the expression and language of Mesulam- delightful).
With the evolution of more complex nervous systems some of its neurons may have been "freed from the household chores of sensation and action" and take on a role "forming alternate and annotated representations" of current events. This is said in another most elegant way by Llinas: "Thinking is the evolutionary internalization of movement."
(NB: The whole notion of the brain making representations of anything is under fire and will be discussed at another time.) "One consequence of this process could be the emergence of an observing self who becomes differentiated from the sensory flux and who can therefore intentionally comment (introspect) on experience."
"Such a capacity for introspection and intentionality may have generated first the sense of a 'commenting self' separate from the experiencing body, then the belief that others also have commenting selves, and, ultimately, that these other commenting selves believe that others also have commenting selves."
Here is where Feldenkrais and the FM community will differ with Mesulam. Is the 'commenting self' ever separate from the experiencing body? Can there be a 'commenting self' without a body or its experiences?
Then Mesulam reminds us that we evolved from the Apes 5 million years ago and subsequently developed a larger cranium, stood erect and moved the larynx lower for improved vocal output. Over the last 50 to 100 thousand years much of the brain has remained structurally the same but is obviously functionally very different to our cave days.
Mesulam argues in part that it is the development of language and civilization that provided communication, recording and passing on of knowledge from one generation to another (we don't have to "re-invent the wheel" so to speak) that has made for changes in brain function. The structure remains the same we now use it differently.
(NB: as an aisde- Mesulam argues that language is a consequence of thought;
"Language ..becomes a consequence of thought, not its cause.").
"..adaptability to change, in fact an overwhelming urge to seek novelty and alternative vantage points, is a major characteristic of the human CNS and the principal determinant of the cognitive relativism."
There it is again- seeking novelty- differences make a difference. Sameness is dulling to life. I wonder from Mesulam's discussion of not having to re-invent the wheel how much in FM do we actually try to re-invent the wheel? The argument is for self determined learning like how we first stand and as distinct from and perhaps excluding academic learning. Is there a way to speed up our learning in FM from other's experiences. Do we have to re-invent the wheel?. My attention was recently brought to Feldenkrais' comments in his book "The Elusive Obvious" about how much he enjoyed readings from science and how much this affected his work. Is there a place for academic learning and some specific direction and structure in our learning?
"The same neural template that enabled the serenity of Ryoanji (see http://en.wikipedia.org/wiki/Ry%C5%8Dan-ji ) has also enabled Auschwitz . It goes without saying that purpose in biology is constrained by survival, not by value. The neural connections that enable the human mind to transcend stimulus-response bonds but do not specify the contents or consequences of the resultant activities".
I think Feldenkrais might disagree here. It can be argued from FM work that in fact during the evolution of communities from cave man to skyscraper man that human emotional behaviour also has evolved in such a way as to contribute to the survival and benefit of the community. Is there is a universality across cultures hidden within the self -that just needs to be activated and contrived dangerous behaviour de-activated?.
Overall, much is familiar in this article with my experience of FM. Some is different especially thought and sensation as something separate from action.
That Feldenkrais' three or four ways to do the same thing is in fact an evolutionary biological feature of the human behaviour is re-assuring to me of the greatness of the work. That adaptability, play and novelty are not only specific to learning in the Feldenkrais Method but are primary agents of the development of human cognitive capabilities. I am always amazed when I read these sorts of science articles that intersect with our FM work that Feldenkrais had put all this together in an even more coherent practical model over 50 years ago.
And finally last words to Mesulam:
"The resultant texture of human existence, based on the flexibility afforded by the neural pathways that link sensation to cognition, is immensely rich but also potentially quite fragile since not all that is novel is necessarily good. The future of the human race, while almost unlimited in its potential, is therefore also more uncertain than that of the frog".
best
Robert Burgess
I present these articles not to promote them or demote them rather as explorations, some fact, some conjecture, some in correct in the understanding of human learning, function and behaviour.
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