Ballet dancers’ brains adapt to stop them going dizzy

Years of training in “spotting”, the technique of quickly and repeatedly bringing your gaze to two specific points in front and behind you, certainly helps, but new research suggests that the brain’s ability to adapt plays a powerful role.

If you’ve ever tried spinning in circles while looking up to the sky, you’ll know the accompanying dizziness that can follow. But what stops ballet dancers, who pirouette endlessly for a living, from falling into each other like a set of dominoes?

Years of training in “spotting”, the technique of quickly and repeatedly bringing your gaze to two specific points in front and behind you, certainly helps, but new research suggests that the brain’s ability to adapt plays a powerful role. And it could help better treat and diagnose people who suffer from chronic dizziness.

Neuroscientists at Imperial College London recruited 29 female ballet dancers and spun them around in a chair in a dark room. When the chair was stopped, the dancers were asked to turn a lever to indicate how quickly they still felt they were spinning. This measured their perception response to dizziness. Eye reflexes – the quick flicking of the eyes from moving around rapidly – were also measured. In normal people, these two responses correlate well, but in the dancers there appeared to be an uncoupling: while their eye reflexes kept going, their perception response fell.

A group of 20 female rowers, who were similar in age and fitness, were also recruited as a control group. Brain scans were then taken to analyse the brain structures of all the individuals.

Powerful resistance

In cases of chronic dizziness, tests are usually taken of the vestibular organs in the inner ear. These fluid-filled organs use tiny hairs to sense the movement of the fluid, which in turn send signals to the brain. The continued movement of fluid explains one of the reasons you can continue to feel dizzy after you’ve stopped moving. But this doesn’t go far enough to explain dizziness in chronic suffers, said Barry Seemungal, co-author of the study, published in Cerebral Cortex.

“We measured sensation perception and eye reflexes and found dancers were much more resistant to non-dancers,” he said. “In the rowers, sensation correlated very well to reflexes, but in dancers the two were not correlated – they had de-coupled. In a person with chronic dizziness, the duration of their perceptual response is much longer; there’s a disproportionately higher reaction compared to a dancer who shows powerful resistance.”

An MRI scan then looked at the amount of grey matter (the bit that calculates) and the white matter (the part of the brain that makes connections) in the cerebellum. This also threw up differences between dancers and non-dancers.

“A statistical comparison between brain structures showed that in dancers an area of the cerebellum was smaller than in the rowers. This part of the brain also known to be involved in processing signals from the ear. And the more experienced the dancer, the smaller it is. The cerebellum can process signals that are then sent to areas of the brain linked to perception. In dancers it reduces the flow of signals – it acts like a gate.”

The researchers then looked at the cerebral cortex, which is associated in perception, and found stronger white matter in the control group. “More white matter means you’re more likely to be dizzy – in dancers we didn’t see it,” Seemungal said.

Seeing is believing

So how can these findings help people with chronic dizziness? For a start, we now have recognition that the brain is the organ that controls balance and, crucially, that it’s able to adapt.

“Traditional testing considers the ear as the organ of balance,” Seemungal said. “I’m a neurologist so I consider it as the brain.”

“The brain takes in lots of different information to make an assessment and compensates if it needs to. The ear is one source, vision is another. If you hear a noise to the right and move your head to look at it, your brain combines the estimates and places greater weight on the more reliable, in this case the eye.”

“But vision can be ambiguous – for example when you’re sat on a train and another one moves and you think you’re the one moving. As a general principle the brain prioritises visual motion over vestibular organs [the ear]. Another example is the ventriloquist’s doll, it combines the auditory and visual inputs but relies more on the visual so you think it’s the doll that’s talking.”

“If your vestibular organs aren’t working well, your brain won’t trust them and even trivial visual stimuli can trigger a dizzy sensation. But traditional testing relies on testing the vestibular organs, which might indicate nothing is wrong.”

People with chronic dizziness can be treated for underlying causes but also longer-term physio treatment. Depending on the form of the condition, this can include exposing them to self-motion (the swaying we all do but don’t notice if we don’t suffer from dizziness) and visual motion to get the brain more habituated.

One lucky find (for the researchers anyway) was that one of the dancers involved in the study later went on to develop chronic dizziness. This enabled the team to test her against their original findings. They found that although her reflex functions had remained the same, her perception response had become stronger.

Professor Nicky Clayton, a Professor of Comparative Cognition at Cambridge and Scientist in Residence at Rambert, the contemporary dance company, said: “As a dancer you learn tricks that allow your body to move in very flamboyant ways but without losing control. One of the tricks I learned was that when you get that sense of spinning, you use your core muscles to pull up; and that you’re disengaging with that feeling of fluidity and creating a stabilising energy.

She added: “Dancers think in very abstract ways … The way in which the brain talks to the cognitive system, whether through its plasticity or psychologically, is more than just spotting. Spotting helps you to focus but it’s not the only thing.”

Simon Lloyd, an ENT specialist, said: “The tests could potentially be useful because at the moment we have no effective way of testing how well parts of the balance system within the brain are working. Testing this would also allow us to measure how people are responding to treatment.”

The Conversation

This article was originally published at The Conversation. Read the original article.

Dancers of Cuba national ballet perform during a rehearsal for Swan Lake in Madrid in 2009. Photo: AFP/Getty Images

Jo Adetunji is the commissioning editor for health and medicine at The Conversation UK.

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How nature created consciousness – and our brains became minds

In From Bacteria to Bach and Back, Daniel C Dennett investigates the evolution of consciousness.

In the preface to his new book, the ­philosopher Daniel Dennett announces proudly that what we are about to read is “the sketch, the backbone, of the best scientific theory to date of how our minds came into existence”. By the end, the reader may consider it more scribble than spine – at least as far as an account of the origins of human consciousness goes. But this is still a superb book about evolution, engineering, information and design. It ranges from neuroscience to nesting birds, from computing theory to jazz, and there is something fascinating on every page.

The term “design” has a bad reputation in biology because it has been co-opted by creationists disguised as theorists of “intelligent design”. Nature is the blind watchmaker (in Richard Dawkins’s phrase), dumbly building remarkable structures through a process of random accretion and winnowing over vast spans of time. Nonetheless, Dennett argues stylishly, asking “design” questions about evolution shouldn’t be ­taboo, because “biology is reverse engin­eering”: asking what some phenomenon or structure is for is an excellent way to understand how it might have arisen.

Just as in nature there is design without a designer, so in many natural phenomena we can observe what Dennett calls “competence without comprehension”. Evolution does not understand nightingales, but it builds them; your immune system does not understand disease. Termites do not build their mounds according to blueprints, and yet the results are remarkably complex: reminiscent in one case, as Dennett notes, of Gaudí’s church the Sagrada Família. In general, evolution and its living products are saturated with competence without comprehension, with “unintelligent design”.

The question, therefore, is twofold. Why did “intelligent design” of the kind human beings exhibit – by building robotic cars or writing books – come about at all, if unintelligent design yields such impressive results? And how did the unintelligent-design process of evolution ever build intelligent designers like us in the first place? In sum, how did nature get from bacteria to Bach?

Dennett’s answer depends on memes – self-replicating units of cultural evolution, metaphorical viruses of the mind. Today we mostly use “meme” to mean something that is shared on social media, but in Richard Dawkins’s original formulation of the idea, a meme can be anything that is culturally transmitted and undergoes change: melodies, ideas, clothing fashions, ways of building pots, and so forth. Some might say that the only good example of a meme is the very idea of a meme, given that it has replicated efficiently over the years despite being of no use whatsoever to its hosts. (The biologist Stephen Jay Gould, for one, didn’t believe in memes.) But Dennett thinks that memes add something important to discussions of “cultural evolution” (a contested idea in its own right) that is not captured by established disciplines such as history or sociology.

The memes Dennett has in mind here are words: after all, they reproduce, with variation, in a changing environment (the mind of a host). Somehow, early vocalisations in our species became standardised as words. They acquired usefulness and meaning, and so, gradually, their use spread. Eventually, words became the tools that enabled our brains to reflect on what they were ­doing, thus bootstrapping themselves into full consciousness. The “meme invasion”, as Dennett puts it, “turned our brains into minds”. The idea that language had a critical role to play in the development of human consciousness is very plausible and not, in broad outline, new. The question is how much Dennett’s version leaves to explain.

Before the reader arrives at that crux, there are many useful philosophical interludes: on different senses of “why” (why as in “how come?” against why as in “what for?”), or in the “strange inversions of reasoning” offered by Darwin (the notion that competence does not require comprehension), Alan Turing (that a perfect computing machine need not know what arithmetic is) and David Hume (that causation is a projection of our minds and not something we perceive directly). Dennett suggests that the era of intelligent design may be coming to an end; after all, our best AIs, such as the ­AlphaGo program (which beat the human European champion of the boardgame Go 5-0 in a 2015 match), are these days created as learning systems that will teach themselves what to do. But our sunny and convivial host is not as worried as some about an imminent takeover by intelligent machines; the more pressing problem, he argues persuasively, is that we usually trust computerised systems to an extent they don’t deserve. His final call for critical thinking tools to be made widely available is timely and admirable. What remains puzzlingly vague to the end, however, is whether Dennett actually thinks human consciousness – the entire book’s explanandum – is real; and even what exactly he means by the term.

Dennett’s 1991 book, Consciousness Explained, seemed to some people to deny the existence of consciousness at all, so waggish critics retitled it Consciousness Explained Away. Yet it was never quite clear just what Dennett was claiming didn’t exist. In this new book, confusion persists, owing to his reluctance to define his terms. When he says “consciousness” he appears to mean reflective self-consciousness (I am aware that I am aware), whereas many other philosophers use “consciousness” to mean ordinary awareness, or experience. There ensues much sparring with straw men, as when he ridicules thinkers who assume that gorillas, say, have consciousness. They almost certainly don’t in his sense, and they almost certainly do in his opponents’ sense. (A gorilla, we may be pretty confident, has experience in the way that a volcano or a cloud does not.)

More unnecessary confusion, in which one begins to suspect Dennett takes a polemical delight, arises from his continued use of the term “illusion”. Consciousness, he has long said, is an illusion: we think we have it, but we don’t. But what is it that we are fooled into believing in? It can’t be experience itself: as the philosopher Galen Strawson has pointed out, the claim that I only seem to have experience presupposes that I really am having experience – the experience of there seeming to be something. And throughout this book, Dennett’s language implies that he thinks consciousness is real: he refers to “conscious thinking in H[omo] sapiens”, to people’s “private thoughts and experiences”, to our “proper minds, enculturated minds full of thinking tools”, and to “a ‘rich mental life’ in the sense of a conscious life like ours”.

The way in which this conscious life is allegedly illusory is finally explained in terms of a “user illusion”, such as the desktop on a computer operating system. We move files around on our screen desktop, but the way the computer works under the hood bears no relation to these pictorial metaphors. Similarly, Dennett writes, we think we are consistent “selves”, able to perceive the world as it is directly, and acting for rational reasons. But by far the bulk of what is going on in the brain is unconscious, ­low-level processing by neurons, to which we have no access. Therefore we are stuck at an ­“illusory” level, incapable of experiencing how our brains work.

This picture of our conscious mind is rather like Freud’s ego, precariously balan­ced atop a seething unconscious with an entirely different agenda. Dennett explains wonderfully what we now know, or at least compellingly theorise, about how much unconscious guessing, prediction and logical inference is done by our brains to produce even a very simple experience such as seeing a table. Still, to call our normal experience of things an “illusion” is, arguably, to privilege one level of explanation arbitrarily over another. If you ask me what is happening on my computer at the moment, I shall reply that I am writing a book review on a word processor. If I embarked instead on a description of electrical impulses running through the CPU, you would think I was being sarcastically obtuse. The normal answer is perfectly true. It’s also true that I am currently seeing my laptop screen even as this experience depends on innumerable neural processes of guessing and reconstruction.

The upshot is that, by the end of this brilliant book, the one thing that hasn’t been explained is consciousness. How does first-person experience – the experience you are having now, reading these words – arise from the electrochemical interactions of neurons? No one has even the beginnings of a plausible theory, which is why the question has been called the “Hard Problem”. Dennett’s story is that human consciousness arose because our brains were colonised by word-memes; but how did that do the trick? No explanation is forthcoming. Dennett likes to say the Hard Problem just doesn’t exist, but ignoring it won’t make it go away – even if, as his own book demonstrates, you can ignore it and still do a lot of deep and fascinating thinking about human beings and our place in nature.

Steven Poole’s books include “Rethink: the Surprising History of New Ideas” (Random House Books)

This article first appeared in the 16 February 2017 issue of the New Statesman, The New Times