Monthly Archives: July 2015

The power of words

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ScienceDaily has an item (here) on an interesting paper. (B. Boutonnet, G. Lupyan. Words Jump-Start Vision: A Label Advantage in Object Recognition. Journal of Neuroscience, 2015; 35 (25): 9329 DOI: 10.1523/JNEUROSCI.5111-14.2015)

The researchers demonstrated how words can affect perception. A particular wave that occurs a tenth of a second after a visual image appears was enhanced by a matching word but not by a matching natural sound. And the word made the identification of the visual quicker but the natural sound did not. For example a picture of a dog, the spoken word ‘dog’, and a dog’s bark would be a set.

They believe this is because the word is about a general category and the natural sound is a specific example from that category. Symbols such as words are the only way to indicate categories. “Language allows us this uniquely human way of thinking in generalities. This ability to transcend the specifics and think about the general may be critically important to logic, mathematics, science, and even complex social interactions.“

Here is the abstract: “People use language to shape each other’s behavior in highly flexible ways. Effects of language are often assumed to be “high-level” in that, whereas language clearly influences reasoning, decision making, and memory, it does not influence low-level visual processes. Here, we test the prediction that words are able to provide top-down guidance at the very earliest stages of visual processing by acting as powerful categorical cues. We investigated whether visual processing of images of familiar animals and artifacts was enhanced after hearing their name (e.g., “dog”) compared with hearing an equally familiar and unambiguous nonverbal sound (e.g., a dog bark) in 14 English monolingual speakers. Because the relationship between words and their referents is categorical, we expected words to deploy more effective categorical templates, allowing for more rapid visual recognition. By recording EEGs, we were able to determine whether this label advantage stemmed from changes to early visual processing or later semantic decision processes. The results showed that hearing a word affected early visual processes and that this modulation was specific to the named category. An analysis of ERPs showed that the P1 was larger when people were cued by labels compared with equally informative nonverbal cues—an enhancement occurring within 100 ms of image onset, which also predicted behavioral responses occurring almost 500 ms later. Hearing labels modulated the P1 such that it distinguished between target and nontarget images, showing that words rapidly guide early visual processing.”

 

The center of the universe

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When we are conscious we look out at the world through a large hole in our heads between our noses and our foreheads, or so it seems. It is possible to pin-point the exact place inside our heads which is the ‘here’ to which everything is referenced. That spot is about 4-5 centimeters behind the bridge of the nose. Not only sight but hearing, touch and the feelings from inside our bodies are some distance in some direction from that spot. As far as we are concerned, we carry the center of the universe around in our heads.

Both our sensory system and our motor system use this particular three dimensional arrangement centered on that particular spot and so locations are the same for both processes. How, why and where in the brain is this first person, ego-centric space produced? Bjorn Merker has a paper in a special topic issue of Frontiers of Psychology, Consciousness and Action Control (here). The paper is entitled “The efference cascade, consciousness and its self: naturalizing the first person pivot of action control”. He believes evidence points to the roof of the mid-brain, the superior colliculus.

If we consider the center of our space, then attention is like a light or arrow pointing from the center to a particular location in that space and what is in it. That means that we are oriented in that direction. “The canonical form of this re-orienting is the swift and seamlessly integrated joint action of eyes, ears (in many animals), head, and postural adjustments that make up what its pioneering students called the orienting reflex.”

This orientation has to occur before any action directed at the target or any examination of the point of interest by our senses. First the orientation and then the focus of attention. But how does the brain decide which possible focus of attention is the one to orient towards. “The superior colliculus provides a comprehensive mutual interface for brain systems carrying information relevant to defining the location of high priority targets for immediate re-orienting of receptor surfaces, there to settle their several bids for such a priority location by mutual competition and synergy, resulting in a single momentarily prevailing priority location subject to immediate implementation by deflecting behavioral or attentional orientation to that location. The key collicular function, according to this conception, is the selection, on a background of current state and motive variables, of a single target location for orienting in the face of concurrent alternative bids. Selection of the spatial target for the next orienting movement is not a matter of sensory locations alone, but requires access to situational, motivational, state, and context information determining behavioral priorities. It combines, in other words, bottom-up “salience” with top-down “relevance.””

We are provided with the illusion that we sit behind our eyes and experience the world from there and from there we plan and direct our actions. A lot of work and geometry that we are unaware of goes into this illusion. It allows us to integrate what we sense with what we do, quickly and accurately.

 

Making sense of the sense of smell

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This is another post on Morsella’s ideas.

In developing the Passive Frame theory of consciousness, the group uses olfaction as the sensory source to focus on. This seems surprising at first, but they have good reasons for this.

First, it is an old system from an evolutionary viewpoint. As in this quote from Shepherd: “the basic architecture of the neural basis of consciousness in mammals, including primates, should be sought in the olfactory system, with adaptations for the other sensory pathways reflecting their relative importance in the different species”.

Second, its connections are simple compared to vision and hearing. Olfactory signals go straight to the cortex rather than arriving in the cortex via the thalamus and they enter an old part of the cortex, the paleocortex rather than the neocortex (which has primary processing areas for the other senses). The processing of smell is more or less confined to one area in the frontal region and does not extend to the extensive areas at the back of the brain where visual and auditory processing occurs. The sense of smell is much easier to track anatomically than the other ‘higher’ senses. To understand minimal consciousness, it is reasonable to use the least elaborate sense as a model.

Third, looking at what lesions interfere with olfactory consciousness, it seems that connections outside the cortex are not needed for awareness of odours. This implies that at a basic level consciousness does not require the thalamus or mid-brain areas (although consciousness of other senses does require those areas). Some links to the thalamus and other areas may be involved in further processing smell signals but not in being conscious of them.

Fourth, the addition of a smell into the contents of consciousness has a sort of purity. The sense is only there when it is there. We are aware of silence and of complete darkness but we are not aware of a lack of odour unless we question ourselves. If odours are at very low concentrations or if we have habituated to them because they are not changing in concentration, we are not conscious of those odours and also not conscious of their absence. “The experiential nothingness associated with olfaction yields no conscious contents of any kind to such an extent that, absent memory, one in such a circumstance would not know that one possessed an olfactory system.” So addition of a smell to the contents of consciousness is a distinct change in awareness and can of itself focus attention on it.

Fifth, olfaction is not connected with a number of functions. There are no olfactory symbols being manipulated and the like. It is difficult to hold olfactory ‘images’ in working memory. Also “olfactory experiences are less likely to occur in a self-generated, stochastic manner: Unlike with vision and audition, in which visually-rich daydreaming or ‘ear worms’ occur spontaneously during an experiment and can contaminate psychophysical measures, respectively, little if any self-generated olfactory experiences could contaminate measures.”

As well as these reasons given by Morsella in justifying the choice of olfaction in developing the Passive Frame theory, it occurs to me that there is a significant difference in memory. There is a type of recall prompted by smell that seems instantaneous, effortless and very detailed. For example, when you enter a house that you have not been in since childhood and the house has changed in so many ways over the years, the first breath gives a forgotten smell and a vivid sense of the original house along with many images from memories you know you could not normally recall. There seems to be some direct line between the memory of a ‘place’ and the faint odour of that place.

This olfactory approach to consciousness does cut away much of the elaborations and fancy details of consciousness and allows the basic essentials to be clearer.

A tiny eye

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Erythropsidinium

A single celled organism called Erythropsidinium has been reported to have a tiny eye. This organism is not a simple bacteria sort of cell but is a eukaryote. It is single celled but has the kind of cell that is found in multicelled organisms like us. It is not a bag of chemicals but is highly organized with a nucleus and organelles. Among the organelles is a little eye and a little harpoon – ‘all the better to hunt with, my dear’. The eye (called an ocelloid) is like a camera with a lens and pigment responders; while the harpoon is a piston that can elongate 20 or so times in length very quickly and has a poison tip. The prey is transparent but has a nucleus that polarizes light and it is the polarized light that the ocelloid detects. This results in the harpoon being aimed in the direction of the prey before it is fired.

That sounds like a link between a sensory organelle and a motor organelle. As far as I can see, it is not known how the linking mechanism works but in a single celled organism the link has to be relatively simple (a mechanical or chemical molecular event or short chain of events). This is like a tiny nervous system but without the nerves. There is a sensor and an actor and in a nervous system there would be a web of inter-neurons that that connected the two and allowed activity to be appropriate to the situation. What ever the link is in Erythropsidinium, it does allow the steering of the harpoon to an effective direction. The cell can move the ocelloid and the harpoon. Are they physically tied together? Or is there more information processing than just a ‘fire’ signal?

This raises an interesting question. Can we say that this organism is aware? If the ability to sense and to act is found coordinated within a single cell – can that cell be said to be aware of its actions and its environment? And if it is aware, is it conscious in some simple way? That would raise the question of whether complexity is a requirement for consciousness. These are semantic arguments, all about how words are defined and not about how the world works.

Content generation for passive frame consciousness

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This is a continuation of posts on Morsella’s passive frame theory of consciousness.

Content is generated by modules that have input from bottom-up sensory paths, and from top-down paths. The generators are sensitive to context – a picture of a snake and a real snake are different. And they are unconscious – we cannot unsee a visual illusion even if we have knowledge of the real presentation.

The contents enter consciousness in an automatic manner. They are pushed in unconsciously not pulled in consciously – they just seem to happen, to ‘pop up’. The contents are under the control of unconscious associations – a word presented as a purely visual stimulus can be a phonetic representation in consciousness.

As well as sensory content generators, there are generators of action-related urges. Morsella uses the example: “when one holds one’s breath while underwater, or runs barefoot across the hot desert sand in order to reach water, one cannot help but consciously experience the inclinations to inhale or to avoid touching the hot sand, respectively. Regardless of the adaptiveness of the expressed actions, the conscious strife triggered by the external stimuli cannot be turned off voluntarily.”

Thus the sensory presentation and the urges are generated in a way that is insulated or encapsulated from voluntary control. “Thus, although inclinations triggered by external stimuli can be behaviorally suppressed, they often cannot be mentally suppressed. One can think of many cases in which externally triggered conscious contents are more difficult to control than is overt behavior.”

The contents of consciousness are independent of one another whether they are memories, stimuli from the environment are whatever, and this is adaptive. Cross contamination would interfere with successful behavior. The safer influence by context-sensitivity is unconscious, not the result of a conscious whim. This is an important point of difference with some other theories. “This view stands in contrast to several influential theoretical frameworks in which both the activation of, and nature of, conscious contents are influenced by what can be regarded as over-arching goals or current task demands. Because of the principle of encapsulation, conscious contents cannot influence each other either at the same time nor across time, which counters the everyday notion that one conscious thought can lead to another conscious thought. In the present framework, not only do contents not influence each other in the conscious field, but as Merker concludes, content generators cannot communicate the content they generate to another content generator. For example, the generator charged with generating the color orange cannot communicate ‘orange’ to any other content generator, for only this generator (a perceptual module) can, in a sense, understand and instantiate ‘orange.’ Hence, if the module charged with a particular content is compromised, that content is gone from the conscious field and no other module can ‘step in’ to supplant that content. As Merker notes, in constructing the conscious field, modules can send, not messages with content, but only ‘activation’ to each other. This activation, in turn, influences whether the receiver module will generate, not the kind of content generated by the module from which it received activation, but rather its own kind of content (e.g., a sound). Because messages of content cannot be transmitted to other content generators, the neural correlates of the content for X must include activation of the module that generates X, for a content cannot be segregated from the process by which it was engendered, as stated above.” Thus it seems that the contents of consciousness are not marshalled onto a stage or theatre but rather a network is formed connecting the original generators or modules.

The mosiac of independent content is discontinuous and arises in each conscious moment which quickly follow one another. What is watching this content? The passive frame theory says: “ “Importantly, the collective influence of the combination of contents in the conscious field is not toward the conscious field itself; instead … the conscious field is apprehended by the (unconscious) mechanisms comprising the skeletomotor output system. Thus, the conscious contents of blue, red, a smell, or the urge to blink are the tokens of a mysterious language understood, not by consciousness itself (nor by the physical world), but by the unconscious action mechanisms of skeletomotor output system. Why do things appear the way they do in the field? Because, in order to benefit action selection, they must differentiate themselves from all other tokens of the field—across various modalities/systems but within the same decision space.”

I have to add that this may indeed be the original evolutionary reason for consciousness and it may be the over-riding determinant of the mechanisms involved. However, it seems to me that having created a moment of consciousness the brain is loath to throw it away. It is somehow saved and used to form an episodic memory.

A train of discrete places

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Place cells are active when an animal is moving about, when it is learning a route, when it is revisiting the path during sleep, when it is planning a route and when it is taking that route. The place cells are active in a sequence that defines the route.

ScienceDaily has an item (here) on a recent paper (B. E. Pfeiffer, D. J. Foster. Autoassociative dynamics in the generation of sequences of hippocampal place cells. Science, 2015; 349 (6244): 180). The paper describes the events in remembering a route.

Foster says, “My own introspective experience of memory tends to be one of discrete snapshots strung together, as opposed to a continuous video recording. Our data from rats suggest that our memories are actually organized that way, with one network of neurons responsible for the snapshots and another responsible for the string that connects them.“

The research showed gaps between the ‘snapshot’ discrete memories of a place. “The trajectories that the rats reconstructed weren’t smooth. We were able to see that neural activity ‘hovers’ in one place for about 20 milliseconds before ‘jumping’ to another place, where it hovers again before moving on to the next point. At first, you get a ‘blurry’ representation of point A because a bunch of place cells all around point A fire, but, as time passes, the activity becomes more focused on A. Then the activity jumps to a “blurry” version of B, which then gets focused. We think that there is a whole network of cells dedicated to this process of fine-tuning and jumping. Without it, memory retrieval would be even messier than it is.“

It seems to me that this discrete series of place memories may well be like consciousness – a discrete train of individual conscious moments rather than a continuous ‘movie’.

Here is the abstract:

“Neuronal circuits produce self-sustaining sequences of activity patterns, but the precise mechanisms remain unknown. Here we provide evidence for autoassociative dynamics in sequence generation. During sharp-wave ripple (SWR) events, hippocampal neurons express sequenced reactivations, which we show are composed of discrete attractors. Each attractor corresponds to a single location, the representation of which sharpens over the course of several milliseconds, as the reactivation focuses at that location. Subsequently, the reactivation transitions rapidly to a spatially discontiguous location. This alternation between sharpening and transition occurs repeatedly within individual SWRs and is locked to the slow-gamma (25 to 50 hertz) rhythm. These findings support theoretical notions of neural network function and reveal a fundamental discretization in the retrieval of memory in the hippocampus, together with a function for gamma oscillations in the control of attractor dynamics.”

Lingua Franca of the brain

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Ezequiel Morsella has been kind enough to send me more information on the Passive Frame theory of consciousness. So here is another posting on ideas from that source.

From time to time I encounter notions of there being a ‘language of the brain’ or a brain coding system. Although I would not say that there was no extra language layer (who knows?), I have never seen the necessity for it. The idea seems a product of thinking of the brain in the context of software algorithms, digital transmission, information theory, universal Turing machines and the like rather than in biological cell to cell communication.

Look at forming and retrieving episodic memories: they are conscious experiences before they are stored and conscious experiences when they are retrieved. Awareness is in the form of consciousness and so is the access of various parts of the brain to information from other parts. We understand movement of ourselves and others in similar terms. The Passive Frame proponents talk of perception-like tokens - “they represent well-crafted representations occurring at a stage of processing between sensory analysis and motor programming” and are presumably accessible to both. Here we can have a lingua franca for sensory-motor interaction.

Of course for both sensory and motor processing we need a space and viewpoint for the perception-like tokens. This is often thought of as a stage or a sensorium, but I like to think of it as a model of the environment with the organism active in it. In this ‘space’ the objects we perceive can be placed and our actions can be simulated.

Humans can detect polarized light

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Here is a most interesting development that fits in with the idea that we are still ignorant of many details of the nervous system. Humans have the ability to perceive polarized light. We are not aware of this sense and do not use it, but it is there. Actually it has been known for sometime but not generally.

The paper by S. Temple (citation below) describes research which started with polarized light sight in sea animals, then its mechanism in humans, and finally it appears to offer a method of diagnosing AMD before it affects vision.

In the paper there are directions for seeing the polarization. I have to say I was skeptical and quite surprised when the faint yellow bowtie appeared and rocked back and forth as I tilted my head. When I stopped moving my head the bowtie disappeared. “We detect the orientation of polarized light using ‘Haidinger’s brushes’, an entoptic visual phenomenon described by Wilhelm Karl von Haidinger in 1844. He reported that when viewing a polarized light field, with no spatial variation in intensity or colour, it was possible for someone with normal sight to perceive a faint pattern of yellow and blue bowtie-like shapes that intersect at the viewer’s point of fixation. Haidinger’s brushes can be observed by looking at a region of blue sky approximately 90° from the sun, particularly around sunset or sunrise, or by looking at a region of white on a liquid crystal display (LCD). The effect vanishes within about 5 s, but can be maintained and/or increased in salience by rotating the eye around the primary visual axis relative to the light field, e.g. tilting one’s head side to side.” Entoptic means that the phenomenon has an origin within the eye rather than the outside world.

The bowties are created by two structures in the eye. The cornea has layers of collagen molecules arranged to create birefringence. This can be thought of as slow and fast orientations depending on the polarization angle of light rays. This interacts with carotenoid pigments in the macula or fovea which are also arranged in a particular way to form an interference filter (dichroic filter). The center of the lens behind the cornea, the center of the macula and the object of visual attention are in a straight line. Therefore the orientation of the collagen, carotenoid pigments and the direction of the light are always the same.

By studying the Haidinger’s brushes in an individual it is possible to examine aspects of the structure of the macula and the cornea.

Here is the abstract:

“Like many animals, humans are sensitive to the polarization of light. We can detect the angle of polarization using an entoptic phenomenon called Haidinger’s brushes, which is mediated by dichroic carotenoids in the macula lutea. While previous studies have characterized the spectral sensitivity of Haidinger’s brushes, other aspects remain unexplored. We developed a novel methodology for presenting gratings in polarization-only contrast at varying degrees of polarization in order to measure the lower limits of human polarized light detection. Participants were, on average, able to perform the task down to a threshold of 56%, with some able to go as low as 23%. This makes humans the most sensitive vertebrate tested to date. Additionally, we quantified a nonlinear relationship between presented and perceived polarization angle when an observer is presented with a rotatable polarized light field. This result confirms a previous theoretical prediction of how uniaxial corneal birefringence impacts the perception of Haidinger’s brushes. The rotational dynamics of Haidinger’s brushes were then used to calculate corneal retardance. We suggest that psychophysical experiments, based upon the perception of polarized light, are amenable to the production of affordable technologies for self-assessment and longitudinal monitoring of visual dysfunctions such as age-related macular degeneration.”

Citation: Temple SE, McGregor JE, Miles C, Graham L, Miller J, Buck J, Scott-Samuel NE, Roberts NW. 2015 Perceiving polarization with the naked eye: characterization of human polarization sensitivity. Proc. R. Soc. B 282: 20150338. http://dx.doi.org/10.1098/rspb.2015.0338

 

Passive Frame Theory

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ScienceDaily has an item (here) on a paper by Morsella and others on the Passive Frame Theory of consciousness. This theory is one of my favorites!!

The passive frame presents information but does not create or act on that information. This consciousness is like an interpreter Morsella says, “the information we perceive in our consciousness is not created by conscious processes, nor is it reacted to by conscious processes. Consciousness is the middle-man, and it doesn’t do as much work as you think.” It is intuitive to think that consciousness is in control of the things it reports (actions, thoughts, feelings, perceptions). But really consciousness simply passively presents these things.

Morsella also says that consciousness is not a connected stream. “One thought doesn’t know about the other, they just often have access to and are acting upon the same unconscious information. You have one thought and then another, and you think that one thought leads to the next, but this doesn’t seem to be the way the process actually works.”

This theory also puts action at a more central place in the function of consciousness than perception.

I do not have access to the original paper (Morsella, Godwin, Jantz, Krieger, Gazzaley; Homing in on Consciousness in the Nervous System: An Action-Based Synthesis; Behavioral and Brain Sciences 2015). But here is the abstract:

“What is the primary function of consciousness in the nervous system? The answer to this question remains enigmatic, not so much because of a lack of relevant data, but because of the lack of a conceptual framework with which to interpret the data. To this end, we developed Passive Frame Theory, a internally-coherent framework that, from an action-based perspective, synthesizes empirically supported hypotheses from diverse fields of investigation. The theory proposes that the primary function of consciousness is well-circumscribed, serving the somatic nervous system. Inside this system, consciousness serves as a frame that constrains and directs skeletal muscle output, thereby yielding adaptive behavior. The mechanism by which consciousness achieves this is more counterintuitive, passive, and ‘low level’ than the kinds of functions that theorists have previously attributed to consciousness. Passive Frame Theory begins to illuminate (a) what consciousness contributes to nervous function, (b) how consciousness achieves this function, and (c) the neuroanatomical substrates of conscious processes. Our untraditional, action-based perspective focuses on olfaction instead of on vision and is descriptive (describing the products of nature as they evolved to be) rather than normative (construing processes in terms of how they should function). Passive Frame Theory begins to isolate the neuroanatomical, cognitive-mechanistic, and representational (e.g., conscious contents) processes associated with consciousness.”

 

Colour words

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It is well known that all languages do not have words for what we would call the basic colours of the rainbow – red, orange, yellow, green, blue, purple – along with white and black. Why can this be so?

First we can get rid of the idea that because they have no word for a colour, they cannot see it? Of course they can see it, they simply have no category that for that particular colour. Take a language without a word for blue: we would call a darker blue a shade of black and a lighter blue as a shade of white. To wonder why we would answer this way is like wondering why someone calls both straw and apricot shades of yellow. It is not that they cannot see the difference but that they have not formed those particular categories (because they have never spent hours picking the colours of paints, for example). How many colour names we have and the exact lines of demarcation between them depend on the culture/language we live in. When we see a colour in front of us, we see the visual perception and not the category/word/concept of a particular colour. We can compare two shades in front of us and say whether they are the same or different even if we only have one colour word for both of them.

Seeing is one thing but saying is another. All words are categories or concepts and encompass a good deal of variation. In the ‘space-landscape’ of colour, words are like large countries. As children we learn the geography of this space and the borders of each word’s domain. When we are asked to name a colour, we use the word that is the colour’s best category. We sort of understand where in the landscape that colour is and therefore which country it is in. To communicate we need to more of less agree on the borders of the categories and the word of each – otherwise that is no communication. If you say it is a red flower, I will imagine an archetypal flower with an average red colour.

Our culture does more than that. Culture can make connections between objects and colours. Some objects get defined by their colour. What colour is the sky? It is blue. It is a well known fact that the sky is blue. But the sky is not always blue – black on a dark night, various shades of grey (from almost white to quite dark grey with clouds), pink in the dawn, orange and red in the sunset, green with northern lights. Water is also blue by agreement although it is often grey, green, brown, yellow or red. If I think of leaf, green comes along. If I think of lemon, I also bring up yellow. The sky and blue is one of these conventional pairings. But where the colour is important it (in a sense) splits the object concept. It matters whether a wine is red or white, a chess-piece is black or white. The culture will force the noticing of colour when it is important in that culture. Quite often colours are identified by an object (like the apricot and straw mentioned above). This has been going on for a long time: orange from a Persian word for the fruit, yellow from a West German for gold, green from an old Germanic word of new growth, purple from the Greek for a mollusc that gave the royal dye.

Languages acquire colour words over time. Berlin and Kay examined the history of 110 languages and found that words for colour started with light and dark (not just white and black), followed by red (sometimes used as bright coloured), then green and yellow (sometimes together and then separating), then blue. Other colours where added later brown and orange (together sometimes at first), purple, pink, grey. Then we have many, many subcategories (sky blue, pea green) and border ones (aquamarine/turquoise at the green-blue border). I notice that lately when people list basic colours, they include pink along with the primary colours. This is new and implies that red has split to be red and pink. People do not want to call a pink thing red.

Unless it is very important, it seems that colour can be omitted from a memory. It is surprising how little we remember the colour of things. We can see things every day and not be able to remember their colour. There sometimes is simply no reason to remember.

We cannot know what people experience from looking at the words they have. The ancient Greeks lacked many colour words. But the idea that, “It seemed the Greeks lived in a murky and muddy world, devoid of color, mostly black and white and metallic, with occasional flashes of red or yellow”, is just wrong. Their poetry is not full of colourful images but that does not mean that their live was devoid of colour.