How Thinking Can Change the Brain

Such discoveries of how the mind can change the brain have a spooky quality that makes you want to cue the “Twilight Zone” theme, but they rest on a solid foundation of animal studies. Attention, for instance, seems like one of those ephemeral things that comes and goes in the mind but has no real physical presence. Yet attention can alter the layout of the brain as powerfully as a sculptor’s knife can alter a slab of stone.

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Although science and religion are often in conflict, the Dalai Lama takes a different approach. Every year or so the head of Tibetan Buddhism invites a group of scientists to his home in Dharamsala, in Northern India, to discuss their work and how Buddhism might contribute to it.

In 2004 the subject was neuroplasticity, the ability of the brain to change its structure and function in response to experience. The following are vignettes adapted from “Train Your Mind, Change Your Brain,” which describes this emerging area of science:

The Dalai Lama, who had watched a brain operation during a visit to an American medical school over a decade earlier, asked the surgeons a startling question: Can the mind shape brain matter?

Over the years, he said, neuroscientists had explained to him that mental experiences reflect chemical and electrical changes in the brain. When electrical impulses zip through our visual cortex, for instance, we see; when neurochemicals course through the limbic system we feel.

But something had always bothered him about this explanation, the Dalai Lama said. Could it work the other way around? That is, in addition to the brain giving rise to thoughts and hopes and beliefs and emotions that add up to this thing we call the mind, maybe the mind also acts back on the brain to cause physical changes in the very matter that created it. If so, then pure thought would change the brain’s activity, its circuits or even its structure.

One brain surgeon hardly paused. Physical states give rise to mental states, he asserted; “downward” causation from the mental to the physical is not possible. The Dalai Lama let the matter drop. This wasn’t the first time a man of science had dismissed the possibility that the mind can change the brain. But “I thought then and still think that there is yet no scientific basis for such a categorical claim,” he later explained. “I am interested in the extent to which the mind itself, and specific subtle thoughts, may have an influence upon the brain.”

Source:http://s.wsj.net/public/resources/images/OB-AG235_pod_sc_20070118202502.jpg
Sharon Begley with the Dalai Lama at the neuroplasticity meeting in Dharamsala, India, in 2004

The Dalai Lama had put his finger on an emerging revolution in brain research. In the last decade of the 20th century, neuroscientists overthrew the dogma that the adult brain can’t change. To the contrary, its structure and activity can morph in response to experience, an ability called neuroplasticity. The discovery has led to promising new treatments for children with dyslexia and for stroke patients, among others.

But the brain changes that were discovered in the first rounds of the neuroplasticity revolution reflected input from the outside world. For instance, certain synthesized speech can alter the auditory cortex of dyslexic kids in a way that lets their brains hear previously garbled syllables; intensely practiced movements can alter the motor cortex of stroke patients and allow them to move once paralyzed arms or legs.

The kind of change the Dalai Lama asked about was different. It would come from inside. Something as intangible and insubstantial as a thought would rewire the brain. To the mandarins of neuroscience, the very idea seemed as likely as the wings of a butterfly leaving a dent on an armored tank.

***

Neuroscientist Helen Mayberg had not endeared herself to the pharmaceutical industry by discovering, in 2002, that inert pills — placebos — work the same way on the brains of depressed people as antidepressants do. Activity in the frontal cortex, the seat of higher thought, increased; activity in limbic regions, which specialize in emotions, fell. She figured that cognitive-behavioral therapy, in which patients learn to think about their thoughts differently, would act by the same mechanism.

At the University of Toronto, Dr. Mayberg, Zindel Segal and their colleagues first used brain imaging to measure activity in the brains of depressed adults. Some of these volunteers then received paroxetine (the generic name of the antidepressant Paxil), while others underwent 15 to 20 sessions of cognitive-behavior therapy, learning not to catastrophize. That is, they were taught to break their habit of interpreting every little setback as a calamity, as when they conclude from a lousy date that no one will ever love them.

All the patients’ depression lifted, regardless of whether their brains were infused with a powerful drug or with a different way of thinking. Yet the only “drugs” that the cognitive-therapy group received were their own thoughts.

The scientists scanned their patients’ brains again, expecting that the changes would be the same no matter which treatment they received, as Dr. Mayberg had found in her placebo study. But no. “We were totally dead wrong,” she says. Cognitive-behavior therapy muted overactivity in the frontal cortex, the seat of reasoning, logic, analysis and higher thought. The antidepressant raised activity there. Cognitive-behavior therapy raised activity in the limbic system, the brain’s emotion center. The drug lowered activity there.

With cognitive therapy, says Dr. Mayberg, the brain is rewired “to adopt different thinking circuits.”

***

Such discoveries of how the mind can change the brain have a spooky quality that makes you want to cue the “Twilight Zone” theme, but they rest on a solid foundation of animal studies. Attention, for instance, seems like one of those ephemeral things that comes and goes in the mind but has no real physical presence. Yet attention can alter the layout of the brain as powerfully as a sculptor’s knife can alter a slab of stone.

That was shown dramatically in an experiment with monkeys in 1993. Scientists at the University of California, San Francisco, rigged up a device that tapped monkeys’ fingers 100 minutes a day every day. As this bizarre dance was playing on their fingers, the monkeys heard sounds through headphones. Some of the monkeys were taught: Ignore the sounds and pay attention to what you feel on your fingers, because when you tell us it changes we’ll reward you with a sip of juice. Other monkeys were taught: Pay attention to the sound, and if you indicate when it changes you’ll get juice.

After six weeks, the scientists compared the monkeys’ brains. Usually, when a spot on the skin receives unusual amounts of stimulation, the amount of cortex that processes touch expands. That was what the scientists found in the monkeys that paid attention to the taps: The somatosensory region that processes information from the fingers doubled or tripled. But when the monkeys paid attention to the sounds, there was no such expansion. Instead, the region of their auditory cortex that processes the frequency they heard increased.

Through attention, UCSF’s Michael Merzenich and a colleague wrote, “We choose and sculpt how our ever-changing minds will work, we choose who we will be the next moment in a very real sense, and these choices are left embossed in physical form on our material selves.”

The discovery that neuroplasticity cannot occur without attention has important implications. If a skill becomes so routine you can do it on autopilot, practicing it will no longer change the brain. And if you take up mental exercises to keep your brain young, they will not be as effective if you become able to do them without paying much attention.

***

Since the 1990s, the Dalai Lama had been lending monks and lamas to neuroscientists for studies of how meditation alters activity in the brain. The idea was not to document brain changes during meditation but to see whether such mental training produces enduring changes in the brain.

All the Buddhist “adepts” — experienced meditators — who lent their brains to science had practiced meditation for at least 10,000 hours. One by one, they made their way to the basement lab of Richard Davidson at the University of Wisconsin, Madison. He and his colleagues wired them up like latter-day Medusas, a tangle of wires snaking from their scalps to the electroencephalograph that would record their brain waves.

Eight Buddhist adepts and 10 volunteers who had had a crash course in meditation engaged in the form of meditation called nonreferential compassion. In this state, the meditator focuses on unlimited compassion and loving kindness toward all living beings.

As the volunteers began meditating, one kind of brain wave grew exceptionally strong: gamma waves. These, scientists believe, are a signature of neuronal activity that knits together far-flung circuits — consciousness, in a sense. Gamma waves appear when the brain brings together different features of an object, such as look, feel, sound and other attributes that lead the brain to its aha moment of, yup, that’s an armadillo.

Some of the novices “showed a slight but significant increase in the gamma signal,” Prof. Davidson explained to the Dalai Lama. But at the moment the monks switched on compassion meditation, the gamma signal began rising and kept rising. On its own, that is hardly astounding: Everything the mind does has a physical correlate, so the gamma waves (much more intense than in the novice meditators) might just have been the mark of compassion meditation.

Except for one thing. In between meditations, the gamma signal in the monks never died down. Even when they were not meditating, their brains were different from the novices’ brains, marked by waves associated with perception, problem solving and consciousness. Moreover, the more hours of meditation training a monk had had, the stronger and more enduring the gamma signal.

It was something Prof. Davidson had been seeking since he trekked into the hills above Dharamsala to study lamas and monks: evidence that mental training can create an enduring brain trait.

Prof. Davidson then used fMRI imaging to detect which regions of the monks’ and novices’ brains became active during compassion meditation. The brains of all the subjects showed activity in regions that monitor one’s emotions, plan movements, and generate positive feelings such as happiness. Regions that keep track of what is self and what is other became quieter, as if during compassion meditation the subjects opened their minds and hearts to others.

More interesting were the differences between the monks and the novices. The monks had much greater activation in brain regions called the right insula and caudate, a network that underlies empathy and maternal love. They also had stronger connections from the frontal regions to the emotion regions, which is the pathway by which higher thought can control emotions.

In each case, monks with the most hours of meditation showed the most dramatic brain changes. That was a strong hint that mental training makes it easier for the brain to turn on circuits that underlie compassion and empathy.

“This positive state is a skill that can be trained,” Prof. Davidson says. “Our findings clearly indicate that meditation can change the function of the brain in an enduring way.”

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Le Grand collisionneur de hadrons (LHC)

Le Grand collisionneur de hadrons (LHC) est un gigantesque instrument scientifique situé près de Genève, à cheval sur la frontière franco-suisse, à environ 100 mètres sous terre. C’est un accélérateur de particules, avec lequel les physiciens vont étudier les plus petites particules connues : les composants fondamentaux de la matière. Le LHC va révolutionner notre compréhension du monde, de l’infiniment petit, à l’intérieur des atomes, à l’infiniment grand de l’Univers.

ATLAS
Une coupe d’ATLAS
Crédits : CERN

Le Grand collisionneur de hadrons (LHC) est un gigantesque instrument scientifique situé près de Genève, à cheval sur la frontière franco-suisse, à environ 100 mètres sous terre. C’est un accélérateur de particules, avec lequel les physiciens vont étudier les plus petites particules connues : les composants fondamentaux de la matière. Le LHC va révolutionner notre compréhension du monde, de l’infiniment petit, à l’intérieur des atomes, à l’infiniment grand de l’Univers.

Deux faisceaux de particules subatomiques de la famille des « hadrons » (des protons ou des ions de plomb) circuleront en sens inverse à l’intérieur de l’accélérateur circulaire, emmagasinant de l’énergie à chaque tour. En faisant entrer en collision frontale les deux faisceaux à une vitesse proche de celle de la lumière et à de très hautes énergies, le LHC va recréer les conditions qui existaient juste après le Big Bang. Des équipes de physiciens du monde entier analyseront les particules issues de ces collisions en utilisant des détecteurs spéciaux.

Il existe de nombreuses théories quant aux résultats de ces collisions. Les physiciens s’attendent en tous cas à une nouvelle ère de physique, apportant de nouvelles connaissances sur le fonctionnement de l’Univers. Pendant des décennies, les physiciens se sont appuyés sur le modèle standard de la physique des particules pour essayer de comprendre les lois fondamentales de la Nature. Mais ce modèle est insuffisant. Les données expérimentales obtenues grâce aux énergies très élevées du LHC permettront de repousser les frontières du savoir, mettant au défi ceux qui cherchent à confirmer les théories actuelles et ceux qui rêvent à de nouveaux paradigmes.

Installation du tube à ultravide dans ATLAS
Installation du tube à ultravide dans ATLAS

Pourquoi le LHC

Quelques questions sans réponse…

Le LHC a été construit pour aider les scientifiques à répondre à certaines questions essentielles de la physique des particules qui restent sans réponse. L’énergie sans précédent qu’il atteindra pourrait même révéler des résultats tout à fait inattendus.

Pendant les dernières décennies, les physiciens ont pu décrire de plus en plus précisément les particules fondamentales qui constituent l’Univers, ainsi que leurs interactions. Cette compréhension de l’Univers constitue le modèle standard de la physique des particules. Or, ce dernier présente des failles et n’explique pas tout. »Pour combler ces lacunes, les scientifiques ont besoin de données expérimentales, et c’est le LHC qui va permettre de franchir la prochaine étape.

L’œuvre inachevée de Newton : qu’est-ce que la masse ?

D’où vient la masse ? Pourquoi ces minuscules particules ont-elles la masse qui leur est propre ? Pourquoi certaines particules n’en ont-elles pas ? La question fait l’objet de débats. L’explication la plus plausible pourrait être le rôle du boson de Higgs, une particule » essentielle à la cohérence du modèle standard. Théorisée pour la première fois en 1964, cette particule n’a encore jamais été observée.

Les expériences ATLAS et CMS traqueront les signes de cette particule.

Un problème invisible : de quoi est constitué 96% de l’Univers ?

Tout ce que nous voyons dans l’Univers, des fourmis aux galaxies, est constitué de particules ordinaires. Ces particules sont collectivement appelées matière, et elles forment 4% de l’Univers. On pense que le reste de l’Univers est constitué de matière noire et d’énergie sombre, mais celles-ci sont malheureusement difficiles à détecter et à étudier, si ce n’est à travers les forces gravitationnelles qu’elles exercent. L’exploration de la nature de la matière noire et de l’énergie sombre est l’un des plus grands défis de la physique des particules et de la cosmologie d’aujourd’hui.

Les expériences ATLAS et CMS chercheront des particules supersymétriques afin de tester une hypothèse plausible sur la nature de la matière noire.

Le favoritisme de la Nature : pourquoi n’y a-t-il plus d’antimatière ?

Nous vivons dans un monde fait de matière : tout dans l’Univers, nous y compris, est constitué de matière. L’antimatière est comme la sœur jumelle de la matière, mais avec une charge électrique opposée. Lors du Big Bang qui a marqué la naissance de l’Univers, matière et antimatière ont normalement été produites en quantités égales. Cependant, lorsque des particules de matière et d’antimatière se rencontrent, elles s’annihilent mutuellement et se transforment en énergie. D’une façon ou d’une autre, une infime fraction de matière a dû persister pour former l’Univers dans lequel nous vivons aujourd’hui, et dans lequel il ne subsiste pratiquement pas d’antimatière. Pourquoi la Nature semble-t-elle avoir une préférence pour la matière au détriment de l’antimatière ?

L’expérience LHCb cherchera les différences entre matière et antimatière et contribuera à répondre à cette question. De précédentes expériences ont déjà révélé une légère différence de comportement, mais ce qui a été observé jusqu’à présent est loin de suffire à expliquer l’apparent déséquilibre matière-antimatière dans l’Univers.

Les secrets du Big Bang : à quoi ressemblait la matière dans les premiers instants de l’Univers ?

La matière aurait comme point d’origine un cocktail chaud et dense de particules fondamentales, formé une fraction de seconde après le Big Bang. Les physiciens pensent qu’il y avait à cet instant plus de sortes de particules fondamentales qu’il n’en reste aujourd’hui.

Afin d’étudier les particules qui n’existent plus, l’expérience ALICE utilisera le LHC pour recréer des conditions similaires à celles qui régnaient juste après le Big Bang. Le détecteur ALICE a été spécialement conçu pour analyser un état particulier de la matière, appelé plasma de quarks et de gluons, que l’on pense avoir existé juste après la création de l’Univers.

Des mondes cachés : y a-t-il vraiment d’autres dimensions ?

Einstein a démontré que les trois dimensions de l’espace sont liées au temps. Des théories plus récentes proposent l’existence d’autres dimensions spatiales cachées ; la théorie des cordes, par exemple, postule l’existence de six dimensions spatiales supplémentaires qui n’auraient encore jamais été observées. Celles-ci pourraient être détectées à de très hautes énergies ; c’est pourquoi les données recueillies par tous les détecteurs seront soigneusement analysées afin de repérer toute trace d’autres dimensions.

CERN

Une vue d'ATLAS en cours de montage
Une vue d’ATLAS en cours de montage)