Monthly Archives: March 2014

The power of sound

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Using faked sounds, subjects experienced the illusion that their hand was becoming more like marble according to a recent paper (citation below). We should not be as surprised by this illusion as we are. We assume that our perception of the substance of our bodies is not going to change. But in this illusion it does. The subjects watched a small hammer hit their hand. The experimenters slowly changed the sound that the subject heard from the real sound to the sound of a hammer hitting stone. The subjects had the illusion, the marble-hand illusion, that their hand had become dense, hard, stiff and heavy, like stone. Our surprise at this is itself somewhat surprising. Illusions are like that though – in the famous example, we know, we may even have measured, that the lines are the same length but the illusion is still there and the one line still looks longer than the other. At the level perception, an illusion is not touched by our knowledge that it is wrong. This should not be a surprise.

 

 

Why do we even need to perceive the nature of our own flesh to begin with. It does not change. Oh, but it does, sort of. Think of someone with a cast, or wearing armor for some pageant, or thick winter clothing. We change our body-scheme in many ways when we use tools, wear cloths, are injured and so on. The brain has to examine the nature of our bodies and quickly change the body-scheme if necessary. Fiurther, the process of examining the material nature of the world would include our own bodies; to ourselves would require extra work. So for those two reasons alone, it should not surprise us that our body-scheme can be updated by perception.

 

 

But why should sound create so powerful an illusion? We understand the world from our senses. The senses are limited by what they are sensitive to. The eyes are sensitive to the little window of light that we call the visual spectrum and that is processed into colour and brightness and sheen of surfaces. From this we can identify many aspects of objects. Touch and smell give other pieces of information. But only sound really seems to tells us about the inside of an object and the material it is made from. Because matter vibrates when it is stroked, hit, stressed, broken, or bounced, each type of material has very unique sounds. It can tell us about the hidden inside of an object which is not easy to sense (weight, heat conductivity and other perceptions can give interior information but it is spotty). It is likely that hearing takes precedence over other senses when it come to the material of an object. If I see a slat of wood and when I drop it, I hear a metallic sound, I know that it is a metal strip painted to resemble wood. It is not seen as a piece of wood made to sound like metal. It is not easy to fake the sound of a material. That is exactly what is done in this experiment, the sound is faked. People say seeing is believing but when it comes to materials – hearing is believing.

 

 

So the illusion should not surprise us: illusions are not reversed by knowledge; the brain does update the body-scheme; and, sound is a powerful indicator of the nature of material. “When exposed to multisensory signals that correlate in time and space, but provide incongruent cues to body material, the brain can either keep those signals segregated, or else integrate them and resolve the incongruence by updating the perception of body material. The MHI (marble-hand illusion) demonstrates that the brain integrates correlated signals, and quickly updates the body schema, which consistently results in a vivid bodily illusion. ”

 

 

Here is the abstract:

 

Our body is made of flesh and bones. We know it, and in our daily lives all the senses constantly provide converging information about this simple, factual truth. But is this always the case? Here we report a surprising bodily illusion demonstrating that humans rapidly update their assumptions about the material qualities of their body, based on their recent multisensory perceptual experience. To induce a misperception of the material properties of the hand, we repeatedly gently hit participants’ hand with a small hammer, while progressively replacing the natural sound of the hammer against the skin with the sound of a hammer hitting a piece of marble. After five minutes, the hand started feeling stiffer, heavier, harder, less sensitive, unnatural, and showed enhanced Galvanic skin response (GSR) to threatening stimuli. Notably, such a change in skin conductivity positively correlated with changes in perceived hand stiffness. Conversely, when hammer hits and impact sounds were temporally uncorrelated, participants did not spontaneously report any changes in the perceived properties of the hand, nor did they show any modulation in GSR. In two further experiments, we ruled out that mere audio- tactile synchrony is the causal factor triggering the illusion, further demonstrating the key role of material information conveyed by impact sounds in modulating the perceived material properties of the hand. This novel bodily illusion, the ‘Marble-Hand Illusion’, demonstrates that the perceived material of our body, surely the most stable attribute of our bodily self, can be quickly updated through multisensory integration.

ResearchBlogging.org

Senna, I., Maravita, A., Bolognini, N., & Parise, C. (2014). The Marble-Hand Illusion PLoS ONE, 9 (3) DOI: 10.1371/journal.pone.0091688


Editor’s Selection IconThis post was chosen as an Editor's Selection for ResearchBlogging.org

Get over the dualism

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I keep running across advice on how to be happy, less afraid, more effective and similar personal improvements. Most of them are OK and I can see how they would be useful. But some are not and they are finally getting under my skin. These are the ones that propose a state of war between “you” and “your brain”. Surprising in this day and age, there are people who are not trying to help people over their dualism but actually encouraging it.

 

 

I have taken an example: “Why you should treat your brain like an unruly child” by A P Jacobs almost at random. There are many more. The first thing these articles try and instill in the reader is a separation between the self and the brain/mind and a lack of any responsibility of the “I” for what is thought and done. “I don’t trust my brain. It’s got some good qualities, sure, but it needs constant supervision. It’s like an unruly Boston terrier – left to its own devices, it will scamper off and rummage through the garbage can, spreading rotten guacamole all over the house. In my brain’s case, this means the hours spent wallowing in unrealistic worries, time-wasting regret and elaborate revenge fantasies.” This author seems to imply that he is not worrying, regretting and fantasying – it is just his brain that is doing that. It seems that he believes that it is not necessary to find out why he is doing these things and how to avoid ‘wallowing’; it is only necessary to make it stop with some sort of super determination.

 

 

“I have to monitor my thoughts myself. I have appointed myself my brain’s babysitter. Which is why I spend a lot of time thinking about the contents of my thoughts. Dozens of times a day, I like to ask myself: “Hey, what are you thinking about? Is that a good use of your brain?”” So what is happening here? It is not - hey, what am I thinking about? Why am I thinking about that?

 

 

“Unless I’m paying attention to it, here are some of the unpleasant areas my brain likes to wander into…Worries about absurdly unlikely scenarios… Jealousy of people about whom I know practically nothing…Indulging in absurd regrets …Stewing about perceived slights from years ago….Stewing about perceived slights that never actually happened…I have to tell my brain: Stay out of those areas.” So he tells his brain. This is probably not something that works – there is no separate brain willing to listening to some officious disembodied self. Different parts of the brain can communicate through language but not this way.

 

 

“I force my cerebral cortex to get control of my limbic system. To use behavioral economics lingo, I have to make sure my System 2 is in charge of System 1.” So that is what it is? This is crazy. ‘Limbic system’ is an outdated concept that includes the parts of the cortex that are not neo-cortex, the thalamus, and the basal ganglia. Without these there is no consciousness, no memory, no decisions. They work with the neo-cortex and not in opposition. There is no way the cortex can ‘get control’ of the limbic system. They work together or not at all. The writer may be trying to say that he wants to control his emotions – the limbic system was once thought to be about emotion as opposed to rational thought. Or he may be trying to say consciousness as opposed to unconsciousness. System 1 and 2 are more reasonable ways to think of what used to be called conscious and unconscious thought. System 1 is the process that most of the brain uses most of the time. It does not use working memory (and therefore is not restricted to the amount of information being processed at a time and the lack of speed of working memory); it is fast and efficient but it is not brought to consciousness or episodic memory. System 2 uses working memory, is brought to consciousness and is stored in the episodic memory, but it is slow and can only handle a few things at a time. It is, I think, obvious that system 2 cannot control system 1. If he is not talking about avoiding emotion or steering unconscious thought, what else could he be on about. It appears from his examples that he is not a fan of his default mode network and its time-wasting on memory, imagination, day-dreaming and the like. But this impression appears not to be his intent. “Now I’m not saying you should never let your mind wander. In fact, there’s some evidence of the positive effects of daydreaming.” So, positive thoughts from the default network are welcome but not negative ones, he thinks. I have to say that negative thoughts are very often good to have. People who don’t feel pain are always hurting themselves; people who never worry make bad decisions, people who feel no regret do not learn from mistakes.

 

 

What is missing is an appreciation that the brain has evolved to keep us as safe and successful as it can. It is not bad at it either. It is also your brain, part of your body. If you are talking to your brain, it is actually your brain talking to your brain. There is no other you talking. Talking to yourself can work or not work depending on how it is done. Being macho, domineering and Pollyanna-ish is unlikely to be the best way to talk to yourself.

 

 

I explored internal speech in a previous post a way to talk to yourself a way to talk to yourself .

 

 

Forget suppressed memories

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A recent paper (see citation) has put a hole in another remnant of Freud’s influence, that suppressed memories are still active. Freud noticed that we can suppress unwelcome memories. He theorized that the suppressed memories continued to exist in the unconscious mind and could unconsciously affect behaviour. Uncovering these memories and their influence was a large part of psychoanalysis. Understanding whether this theory is valid is important for evaluating recovered memories of abuse and for dealing with post-traunatic stress disorder.

 

 

The question Gagnepain, Henson and Anderson set out to answer was whether successfully suppressed conscious memories were also suppressed unconsciously or whether they were still unconsciously active. They had subjects learn an association between a word and a picture for a number of pairs. After the pairs were well learned the word would bring the picture to mind. Some of the pairs were then deliberately suppressed through the subject attempting to not bring the picture to mind when the word was mentioned. This produced two sets of pictures in the subject’s mind: one set would come easily to mind (unsuppressed) and the other set was very difficult to bring to mind (consciously suppressed). But what would be the unconscious influence of the consciously suppressed pictures? The subjects were shown the pictures after they had been doctored to make them difficult to recognize. The ones that had been suppressed were not easier but harder to recognize then the unsuppressed ones. So the willful suppression weakened the memory consciously and also weakened the unconscious influence. This sequence was followed with scans which indicated that it was not just the retrieval of memories that was changed by the suppression but also the memories themselves. And further it was the visual-sensory aspect of the memories that was disrupted.

 

 

There are of course some flags to put up: the experiments were done on adults and might not apply to children; and, there was no high psychological stress involved that might change the storage or retrieval of highly emotional memories. However the results do fit with a number of other findings about memory, so that it is now unwise to take the Freudian view of suppression as reliable.

 

 

Here is the abstract:

 

“After a trauma, people often suppress intrusive visual memories. We used functional MRI to understand how healthy participants suppress the visual content of memories to overcome intrusions, and whether suppressed content continues to exert unconscious influences. Effective connectivity, representational similarity, and computational analyses revealed a frontally mediated mechanism that suppresses intrusive visual memories by reducing activity in the visual cortex. This reduction disrupted neural and behavioral expressions of implicit memory during a later perception test. Thus, our findings indicate that motivated forgetting mechanisms, known to disrupt conscious retention, also reduce unconscious expressions of memory, pointing to a neurobiological model of this process.

 

Suppressing retrieval of unwanted memories reduces their later conscious recall. It is widely believed, however, that suppressed memories can continue to exert strong unconscious effects that may compromise mental health. Here we show that excluding memories from awareness not only modulates medial temporal lobe regions involved in explicit retention, but also neocortical areas underlying unconscious expressions of memory. Using repetition priming in visual perception as a model task, we found that excluding memories of visual objects from consciousness reduced their later indirect influence on perception, literally making the content of suppressed memories harder for participants to see. Critically, effective connectivity and pattern similarity analysis revealed that suppression mechanisms mediated by the right middle frontal gyrus reduced activity in neocortical areas involved in perceiving objects and targeted the neural populations most activated by reminders. The degree of inhibitory modulation of the visual cortex while people were suppressing visual memories predicted, in a later perception test, the disruption in the neural markers of sensory memory. These findings suggest a neurobiological model of how motivated forgetting affects the unconscious expression of memory that may be generalized to other types of memory content. More generally, they suggest that the century-old assumption that suppression leaves unconscious memories intact should be reconsidered.”

 
ResearchBlogging.org

Gagnepain, P., Henson, R., & Anderson, M. (2014). Suppressing unwanted memories reduces their unconscious influence via targeted cortical inhibition Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1311468111

Brain, Ubuntu and Hegel

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There is a recent paper in Frontiers in Human Neuroscience: Marchetti and Koster, Brain and intersubjectivity: a Hegelian hypothesis on the self-other neurodynamics. (citation below)

 

The authors attempt to show that self-consciousness can be understood in the context of Hegel’s ideas of intersubjectivity. The parts of Hegel that they pick to illustrate the nature of ‘self’ and ‘other’ reminded me of the Bantu idea of ‘ubuntu’. That made me more interested because, to be honest, I have, in the past, ignored Hegel because of my discomfort with some of his spin-offs: Nietzsche, existentialism, psychoanalysis. But I am intrigued by an overlap of neuroscience, Hegel and ubuntu.

 

 

First the neuroscience as the paper puts it forward: what are the steps from simple perception and thinking (consciousness) leading to the more complicated self-consciousness. The authors look at two aspects of the brain, mirror cells and the default mode network. Mirror cells are active for a particular action whether I do the action or experience someone else doing the same action. I do not confuse myself with someone else but I recognize a particular action (an action concept) as the same action just with a different actor. The default mode network seems to do the same thing for mental actions/states (goals, intentions, view-points, beliefs, emotions, values and so on). It is the same idea: the thoughts are the same but associated with different minds. In other words the same neural systems are used to create our ‘self’ and to create someone else. Using the mechanisms we have to understand others, we can understand ourselves, and of course, vice verse.

 

 

Hegel’s answer is, “Self-consciousness exists in and for itself when, and by the fact that, it so exists for another; that is, it exists only in being acknowledged .” Self and other can exist when they have mutual recognition, recognition of separate identity of the other, and recognition of the self by the other. If there is no recogniton by another then I can be conscious of the world but I cannot be conscious of myself as a self-conscious agent.

 

 

I have thought that there was no equivalent in western philosophy for the concept of Ubuntu but Hegel’s statement seems to be one. Ubuntu is the shining ‘halo’ of Nelson Mandela and Desmond Tutu with their big hearts and unerring moral compasses. Wikipedia has a definition by Michael Onyebuchi Eze of the core of ubuntu. “A person is a person through other people strikes an affirmation of one’s humanity through recognition of an ‘other’ in his or her uniqueness and difference. It is a demand for a creative intersubjective formation in which the ‘other’ becomes a mirror (but only a mirror) for my subjectivity. This idealism suggests to us that humanity is not embedded in my person solely as an individual; my humanity is co-substantively bestowed upon the other and me. Humanity is a quality we owe to each other. We create each other and need to sustain this otherness creation. And if we belong to each other, we participate in our creations: we are because you are, and since you are, definitely I am. The ‘I am’ is not a rigid subject, but a dynamic self-constitution dependent on this otherness creation of relation and distance”. This the basic premise that results in a particular type of community, of social interaction, of economy, of justice and it fact all aspects of Bantu life (ideally, that is).

 

 
ResearchBlogging.org

Marchetti, I., & Koster, E. (2014). Brain and intersubjectivity: a Hegelian hypothesis on the self-other neurodynamics Frontiers in Human Neuroscience, 8 DOI: 10.3389/fnhum.2014.00011

What is conscious intent anyway?

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A recent paper (citation below) reports that conscious intent precedes motor preparation activity, and not that motor preparation is well underway before consciousness registers intent. Here is Zschorlich and Köhling conclusion:

“Motor intention (intention in action) describes a process of motor preparation without executing an overt movement. In our study, we explored the link between motor intention in the movement preparatory phase and the motor outcome. The experiments present evidence that the excitability of the agonistic motor system is significantly enhanced when subjects develop an intention to move. The opposite was true for the antagonistic movement direction and muscles. The results presented indicate

that the excitatory cortico-spinal drive is enhanced during directed motor intention. The data shows that movement intention induced during the enhancement of the cortico-spinal pathway was significantly greater than in the no-intention condition, which argues for the movement-specific modulation of cortico-spinal excitability. The results support the hypothesis that conscious intention to move induces the enhancement of target-specific motor circuits prior to overt movement execution. ”

But Neuroskeptic in a recent blog (here) casts doubt on the finding:

“The authors, Zschorlich and Köhling of the University of Rostock, Germany, are weighing into a long-standing debate in philosophy, psychology, and neuroscience, concerning the role of consciousness in controlling our actions. To simplify, one school of thought holds that (at least some of the time), our intentions or plans control our actions. Many people would say that this is what common sense teaches us as well. But there’s an alternative view, in which our consciously-experienced intentions are not causes of our actions but are actually products of them, being generated after the action has already begun. This view is certainly counterintuitive, and many find it disturbing as it seems to undermine ‘free will’. That’s the background. Zschorlich and Köhling say that they’ve demonstrated that conscious intentions do exist, prior to motor actions, and that these intentions are accompanied by particular changes in brain activity. They claim to have done this using transcranial magnetic stimulation (TMS), a way of causing a localized modulation of brain electrical activity….As far as I can see, volunteers could simply have been pressing the TMS button and then moving their wrist of their own accord. Ironically, they might not have consciously intended to do this; they might have really believed that their movements were being externally triggered (by the TMS) even though they themselves were generating them. This can happen: it’s called the ideomotor phenomenon, and is probably the explanation for why people believe in ‘dowsing’ amongst other things.”

Neuroskeptic points out that this possibility could be tested by simply having some of the TMS events be fakes – ie there would be no TMS field on some occasions but the participants would not know this. Either the real and fake TMS events would give the same result (an ideomotor indication) or they would give different results (ideomotor improbable). This was not done.

I had a problem with this paper before I read Neuroskeptic’s useful suggestion. And I have had the same problem with many other papers. In the second paragraph of the introduction they say, “The central question of how the conscious motor intention is connected to complex motor programs still remains unclear. ” I have, always have had, a difficulty with what ‘conscious motor intention’ is supposed to mean. It very obviously does not happen to me. I am conscious, I act, I have intentions – all well and good. But the intentions I am conscious of come fully formed, they ‘pop’ from nowhere (ie they are formed unconsciously). So conscious motor intention can mean one of a number of things: an intention made by some conscious process (never happened to me nor have I found an actual description of how it happened to someone else), an intention that is not made by any sort of process at all and is then rendered conscious (very unbelievable mechanics), or an intention that is made by an unconscious process and is then rendered conscious (a reasonable idea, not a counterintuitive one to me, that the Zschorlich paper purports to disprove). My complaint is that Zschorlich et al have not put forward an alternative that can be believed. Nor have others. It could not be simpler – if I am not conscious of an actual process then it is not a conscious process. This is an old problem for me and one of the reasons I have taken such an interest in consciousness.

ResearchBlogging.org

Zschorlich VR, & Köhling R (2013). How thoughts give rise to action - conscious motor intention increases the excitability of target-specific motor circuits. PloS one, 8 (12) PMID: 24386291

The pulvinar and attention

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“The streetlight effect is a type of observational bias where people only look for whatever they are searching for by looking where it is easiest. The parable is told several ways but includes the following details: A policeman sees a drunk man searching for something under a streetlight and asks what the drunk has lost. He says he lost his keys and they both look under the streetlight together. After a few minutes the policeman asks if he is sure he lost them here, and the drunk replies, no, that he lost them in the park. The policeman asks why he is searching here, and the drunk replies, “this is where the light is.” This is how Wikipedia tells how this old joke gave the streetlight effect its name. The effect seems to me to be common in neuroscience. Many researchers seem to ignore the thalamus and concentrate only on the cortex when trying to understand perception, consciousness, attention, and working memory. Just because it is easier to look only at activity in the cortex does not mean that everything happens there.

 

Part of the thalamus, the pulvinar, has been shown to be involved in attention, especially visual attention. A recent paper (see citation) examines the pulvinar’s role in maintaining attention. This is another bit of evidence pointing to the importance of thalamus-cortex interaction in the areas of perception, consciousness and attention.

 

Attention is marked by synchronous firing in a number of cortical areas that represent the visual item being held in attention. “Simultaneous neural recordings from two cortical areas have suggested that this selective routing depends on the degree of synchrony between neuronal groups in each cortical area . However, it is unclear how different cortical areas synchronize their activity. Although direct interaction between two cortical areas may give rise to their synchrony, an alternative possibility is that a third area, connected to both of them, mediates cortical synchronization…We therefore hypothesized that the pulvinar increases synchrony between sequential processing stages across the visual cortex during selective attention. ”

 

The experimental setup was a screen on which appeared a short cue as to where a trigger was going to appear. The monkey had to hold this cued location in mind during a delay before the trigger appeared. The monkey was to react to the type of trigger and not be distracted by other similar images in other locations. The activity in various brain regions could be examined before, during and after the attention that was forced by the delay between cue and trigger. The activity in three areas was followed: two regions along the ventral visual pathway that are synchronous during visual attention and an area of the pulvinar that was in two-way interaction with both these visual areas. The ventral stream is the ‘what’ visual stream that is involved in object recognition, episodic memory and consciousness (as opposed to the ‘where’ dorsal stream involved in motor control and is largely unconscious). During the attention period these areas had increased activity and were synchronized in the alpha and gamma bands. Further, using conditional Granger causality calculations, it was the pulvinar that was influencing the two visual cortex areas rather than the other way around and rather than the two visual areas influencing each other. This pulvinar driving was only seen during the attention period.

 

The hypothesis, that the pulvinar nucleus of the thalamus maintains attention by increasing “the synchrony between sequential processing stages across the visual cortex”, has some strong corroborating evidence now. Here is the paper’s abstract:

 

“Selective attention mechanisms route behaviorally relevant information through large-scale cortical networks. Although evidence suggests that populations of cortical neurons synchronize their activity to preferentially transmit information about attentional priorities, it is unclear how cortical synchrony across a network is accomplished. Based on its anatomical connectivity with the cortex, we hypothesized that the pulvinar, a thalamic nucleus, regulates cortical synchrony. We mapped pulvino-cortical networks within the visual system, using diffusion tensor imaging, and simultaneously recorded spikes and field potentials from these interconnected network sites in monkeys performing a visuospatial attention task. The pulvinar synchronized activity between interconnected cortical areas according to attentional allocation, suggesting a critical role for the thalamus not only in attentional selection but more generally in regulating information transmission across the visual cortex. ”

 

ResearchBlogging.org

Saalmann, Y., Pinsk, M., Wang, L., Li, X., & Kastner, S. (2012). The Pulvinar Regulates Information Transmission Between Cortical Areas Based on Attention Demands Science, 337 (6095), 753-756 DOI: 10.1126/science.1223082

Out of body - out of memory

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ScienceDaily (here) has an item on an interesting paper: Loretxu Bergouignan, Lars Nyberg, and H. Henrik Ehrsson. Out-of-body–induced hippocampal amnesia. Proceedings of the National Academy of Sciences, March 10, 2014.

 

Our feeling of our bodies is important to storing/retrieving episodic memories. The experimenters had subjects using virtual reality googles which either left them with their own bodies or forced an ‘out-of-body’ illusion. The subjects could remember the events that happened when their body image was not disturbed. When they tried to remember events that happened when they felt out of their bodies – they had difficulty. Henrik Ehrsson is quoted as saying,“The fMRI scans further revealed a crucial difference in activity in the portion of the temporal lobe — the hippocampus — that is known to be central for episodic memories. When they tried to remember what happened during the interrogations experienced out-of-body, activity in the hippocampus was eliminated, unlike when they remembered the other situations. However, we could see activity in the frontal lobe cortex, so they were really making an effort to remember.”

 

I am inclined to think that memory is a question of saving experiences that may be useful. We know that the hippocampus associates our location with events in memory and that it tracks the timing or ordering of events. There is also often a mood and emotional colouring to remembered events. And extremely important is the sense of how much is invested and how much ownership is taken in events. We remember effort. We remember errors. We remember hard decisions. We remember good places and people and we remember bad ones too. To put it simply, we remember what may be useful. What happened when our bodies were not involved is not very useful – it might as well be someone else’s event.

 

I remember things that happened to other people and I can picture them happening to me. But I know that it did not happen to me. My body was not there. Those memories started as words in a story being told to me and they carry that lack of first-hand involvement. What happens with an experience that has neither our own body’s involvement nor someone else’s body? Perhaps it is – no identifiable agent – no memory.

 

 

Do we have a reptilian brain?

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The reptilian brain is a myth that should not be taken seriously and yet is referred to by many writers and is even seen in educational sites for children. It is the idea that we have three brains: a reptilian one, the paleomammalian one and the mammalian one. The story goes that these were acquired one after another during evolution. The details differ with the writer. But it is all a myth based on an idea from the ’70s of Paul MacLean which he republished in 1990. Over the years in has been popularized by Sagan and Koestler among others.

 

So we get self-help like this: “Because until recently in our history, we had been conditioned to operate and function mainly out of the reptilian brain. We had been operating/ manifesting out of the ‘survival’ mode section of the brain. Once you can understand this concerted mental oppression, you can begin to re-train your mind (free yourself from constant reptilian brain generated reaction) and re-set your innate human gift of creative power.” And information for children like this: “Lower animals, such as fish, amphibians, reptiles and birds, don’t do much “thinking,” but instead concern themselves with the everyday business of gathering food, eating, drinking, sleeping, reproducing and defending themselves. These are instinctual processes. Therefore, their brains are organized along the major centers that control these functions. We humans perform these functions as well, and so have a “reptilian” brain built into us. That means we have the same parts of the brain found in reptiles, namely the brain stem and the cerebellum.”

 

Before our present knowledge of the brain and of evolution, the triune brain did not seem a bad idea and it was a simple model to understand. It no longer makes sense but it is still out there being passed on like right-brained vs left-brained and other myths.

 

One problem with the reptilian brain is that we are not evolved from reptiles. The last common link between mammals and reptiles is called amniotes. They were like amphibians but did not need to lay their eggs in water. In other words, they were the first truly land-dwelling vertebrates and all terrestrial vertebrates evolved from them. They did not have a neocortex but they had all the other anatomical parts of the brain. The amniotes evolved into two groups: the diapsids which further evolved into four lines - turtles, lizards/snake, crocodiles, birds; and the synapsids which evolved into mammals. Mammal evolution is separate from reptiles from the earliest terrestrial vertebrates. What is more, the neocortex makes its appearance very early in the synapsids line. The triune story of what animals had what sort of brain is simply not what evolutionary biology has found.

 

Another problem is the divisions of function that the triune model makes. The reptile brain is said to be only concerned with survival, to be reflexive, to act without thought. It is said to contain the basal ganglia and the lower parts of the brain. This would include the cerebellum and the cerebellum is an important sophisticated part of the brain – concerned with most things we do, not reflexive, and essential to many types of thought. The paleomammalian brain was also called the limbic system (another MacLean coinage) and was supposed to deal with feelings and emotions. But the limbic system includes an important part of consciousness and of memory. The neocortex can do very little without those parts of the brain that were labeled limbic. Finally the mammalian brain was said to be the neocortex but the neocortex cannot really be thought of as a brain, as if it could function without the paleocortex and the thalamus. It was said to do all the thinking.

 

The model presumes that birds and reptiles cannot feel or think, which is a preposterous idea. And early mammals could feel, it was supposed, but not think, again not believable. Birds and many reptiles (perhaps all) have a brain area which does not anatomically resemble the neocortex but which develops from the same part of the embryonic brain and has the same functions as the neocortex. All the descendants of amniotes have essentially the same architecture of brain with the same functions. There are differences in proportions, sizes, connections, fine-scale anatomy but not a gross difference of kind in the brains of land vertebrates.

 

Forget all about the triune model of the brain.

 

Communicating in sync

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How do people coordinate their actions; how does communication work; how does it affect people; how do minds get in sync? When people communicate they do get in sync but there is no magical about this. We perceive the outside world including signals as well as scenery, we model this input and think about it, we then can act on the basis of that cognition. The pathways are there for the action-perception cycle whether we are alone or engaged socially. The coupling of the brains of two people in communication has not been studied very often because it is difficult. Figuratively, there is usually only one fMRI scanner and it only holds one person at a time. A paper by Hasson (see citation below) highlights this problem. Here is the abstract and the conclusion.

Cognition materializes in an interpersonal space. The emergence of complex behaviors requires the coordination of actions among individuals according to a shared set of rules. Despite the central role of other individuals in shaping one’s mind, most cognitive studies focus on processes that occur within a single individual. We call for a shift from a single-brain to a multi-brain frame of reference. We argue that in many cases the neural processes in one brain are coupled to the neural processes in another brain via the transmission of a signal through the environment. Brain-to-brain coupling constrains and shapes the actions of each individual in a social network, leading to complex joint behaviors that could not have emerged in isolation.

The structure of the shared external environment shapes neural responses and behavior. Some aspects of the environment are determined by the physical environment. Other aspects, however, are determined by a community of individuals, who together establish a shared set of rules (behaviors) that shape and constrain the perception and actions of each member of the group. For example, human

infants undergo a period of perceptual narrowing whereby younger infants can discriminate between social signals from multiple species and cultures, but older infants fine tune their perception following experience with their native social signals. Coupled brains can create new phenomena, including verbal and nonverbal communication systems and interpersonal social institutions, that could not have emerged in species that lack brain-to-brain coupling. Thus, just as the Copernican revolution simplified rather than complicated understanding of the physical world, embracing brain-to-brain coupling as a reference system may simplify understanding of behavior by revealing new forces that operate among individuals and shape one’s social world.

I found several parts of the paper very interesting. First, he makes the point that language seems to be geared to a 3-8 Hz rhythm. That is about 3 to 8 syllables in a second, and can be found in auditory processing of language, in the sound delivery of speakers and the movements of their mouths. As that rhythm, the theta band in the brain, is a constant beat in all of us when we are awake, it does not have to be created but just aligned between the speaker and listener. The listener will mimic the rhythm of the speaker (and when they speak, they will also imitate the sounds, grammar, words and meaning of their partner in conversation).

Second, communication must be learned because it requires shared rules, usage, language, customs and culture. For babies and song birds, their learning is only really successful in a social context of face to face communication. The learner must understand that this is an actually communication with its teacher or the learner does not learn. “The babbling of a 7-12 month-old infant exhibits a pitch, rhythm and even a syllable structure that is similar to the ambient language.” The adult care-giver has to respond to the babbling of the infant and the infant must react to the caregivers responses – it requires actual social interaction.

Third, in fMRI scans of speakers and listeners, there are activities that would not be noticed if only one of the individuals was scanned. There are areas that are in sync between the two scanners. There are areas in the listener that follow the speaker – like an imitating action. And, surprise, there are areas in the listener that lead the speaker – like a prediction. In other words, the process of listening uses the mechanisms of action without the action.

As indicated in the last two postings – it is not clear that an entirely new brain structure was needed for language or for communication. Tweaks to existing systems in the brain can give us linguistic communication. The idea usually credited to Chomsky of a single (or small number of simultaneous) mutation only 50 to 140 thousand years ago giving a nearly full-blown language facility almost instantaneously has always seemed like a bit of an unlikely miracle. But it also appears to be less and less necessary as language and communication become more understood.

ResearchBlogging.org

Hasson, U., Ghazanfar, A., Galantucci, B., Garrod, S., & Keysers, C. (2012). Brain-to-brain coupling: a mechanism for creating and sharing a social world Trends in Cognitive Sciences, 16 (2), 114-121 DOI: 10.1016/j.tics.2011.12.007

Language, music and echolocation

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In the immediately previous posting, the main idea was that linguistic and musical communication shared the same syntactic processing in the brain but not the same semantic meaning processing. How can they share syntax? We need to look at communication and at syntax.

 

The simplest type of human communication is non verbal signals: things like posture, facial expression, gestures, tone of voice. They are in effect contagious: if you are sad, I will feel a little sad, if I then cheer up, you may too. The signals are indications of emotional states and we tend to react to another’s emotional state by a sort of mimicry that puts us in sync with them. We can carry on a type of emotional conversation in this way. Music appears to use this emotional communication – it causes emotions in us without any accompanying semantic messages. It appears to cause that contagion with three aspects: the rhythmic rate, the sound envelope and the timbre of the sound. For example a happy musical message has a fairly fast rhythm, flat loudness envelop with sharp ends, lots of pitch variation and a simple timbre with few harmonics. Language seems to use the same system for emotion, or at least some emotion. The same rhythm, sound envelope and timbre is used in the delivery of oral language and it carries the same emotional signals. Whether it is music or language, this sound specification cuts right past the semantic and cognitive processes and goes straight to the emotional ones. Language seems to share these emotional signals with music but not the semantic meaning that language contains.

 

Syntax has a slippery meaning. Its many definitions usually apply to language and it is extended to music as a metaphor. But – if we look at the idea in a more basic way we can see how important this is to processing sound. When we get visual information it is two dimensional because the retina is a surface with two dimensions and the maps of the retina on the cortex are also in two dimensions. Perceptional processing adds depth for a third dimension. But sound comes to us with one dimension because the cochlea is essentially a spiral line. It is mapped as a line on the cortex. Perception gives us a direction for the source of the sound and sometimes a feeling of distance. The identification of what is in the visual field (objects, movement etc.) is perceived by a different process than the identification of what is in a sound. As with all the senses, in perception we are trying to model the environment and events in it. Sound is no different, the meaning of sounds is what we can learn from them about what is happening in the world. This is just like vision which gains meaning from the model of the environment and events in it that it produces. Language and music must be processed by the sound perception system because they come to us as sounds.

 

One description of syntax is that it deals with trains of sound that are complex, have hierarchical patterns, are abstract, have rigid or probabilistic relationships between entities (or rules). It could be presumed that any domain that involves such trains of sound would be processed, as language and music are, in a syntactical manner. The hierarchy would be established, the abstract patterns and relationships identified. The beauty of the train of sound would be appreciated. The entities resulting from this processing would be available for semantic or other processes. There is no reason to rule out a general syntactical processing system, and there is no reason why the domains of sound that use it need to be similar in the sense that they can be mapped one-to-one. Music need not have an exact equivalent of a sentence.

 

If we looked for them, there may be other domains that use the same type of analysis – perhaps all trains of sound to a certain extent. How do we know that a sound (with its echoes) is thunder rather than a gun shot or a dynamite explosion? Perhaps the sound is processed into a hierarchy of direct sounds and echoes with particular sorts of patterns. Ah thunder, we think. This idea of echo processing is intriguing – it would seem, like language and music, to have a syntax that is complex, hierarchical, etc. Some animals, and the humans who have learned it, use echolocation. Would this not be a candidate for the syntactical type of pattern identification? We do not postulate a newish and dedicated visual process to explain reading, and likewise we do not need a newish and dedicated sound process to explain syntactical processing of language. We can be using a system that is very old and only mildly tweaked for language, for music, for echoes.

 

The ingredients of music that appear to be a syntax-like architecture are: there are scales of permissible notes, chords based on those scales and key structures based on changes of chords used within a piece of music. There are similar hierarchies in rhythm patterns with different note lengths and emphasis, organized into bars and the bars into larger patterns. But when these sorts of regularities are compared to words, phrases, sentences and other hierarchies in language, the match is weak at the detailed level.

 

It would be surprising if language and music shared a functional area of the brain that was not more general in nature given the lack of detailed parallels between the structure of language and music.

 

So, is there any evidence that echolocation shares any processing with language and music? There is no real evidence that I can find. A recent paper (citation below) by Thaler, Arnott and Goodale appears to rule out the possibility, but on reflection does not. Here is the abstract:

 

A small number of blind people are adept at echolocating silent objects simply by producing mouth clicks and listening to the returning echoes. Yet the neural architecture underlying this type of aid-free human echolocation has not been investigated. To tackle this question, we recruited echolocation experts, one early- and one late-blind, and measured functional brain activity in each of them while they listened to their own echolocation sounds.

 

When we compared brain activity for sounds that contained both clicks and the returning echoes with brain activity for control sounds that did not contain the echoes, but were otherwise acoustically matched, we found activity in calcarine cortex in both individuals. Importantly, for the same comparison, we did not observe a difference in activity in auditory cortex. In the early-blind, but not the late-blind participant, we also found that the calcarine activity was greater for echoes reflected from surfaces located in contralateral space. Finally, in both individuals, we found activation in middle temporal and nearby cortical regions when they listened to echoes reflected from moving targets.

 

These findings suggest that processing of click-echoes recruits brain regions typically devoted to vision rather than audition in both early and late blind echolocation experts.

 

The actual location is done in the otherwise unused visual cortex (calcarine). This may be a situation like language where the semantic meaning is extracted in parts of the cortex that are not associated with auditory perception. It seems that echolocation does not require extraordinary auditory perception but it does required a systematic attention to sound. So a fairly normal sense of hearing is able to provide to the visual part of the cortex the input it requires (in a trained blind individual) to do echolocation. That input is likely to include a sophisticated pattern identification of the echoes. “All subjects also show BOLD activity in the lateral sulcus (i.e. Auditory Complex) of the left and right hemispheres and adjacent and inferior to the right medial frontal sulcus. The former likely reflects the auditory nature of the stimuli. The latter most likely reflects the involvement of higher order cognitive and executive control processes during task performance.” This description and the areas in the illustrations could be parts of the Broca’s and Wernicke’s areas, the areas that were shown to be active in language and music communication.
ResearchBlogging.org

Thaler, L., Arnott, S., & Goodale, M. (2011). Neural Correlates of Natural Human Echolocation in Early and Late Blind Echolocation Experts PLoS ONE, 6 (5) DOI: 10.1371/journal.pone.0020162