martedì 30 novembre 2010

An Odyssey Through the Brain

O cerebro é uma ferramenta maravilhosa...


Who has seen the mind? Neither you nor I — nor any of the legions of neuroscientists bent on opening the secrets of that invisible force, as powerful and erratic as the wind.

FROM PRIMITIVE TO NEON It is only fitting that the story of the brain should be a visual one, for the visuals had the ancients fooled for millenniums. The brain was so irredeemably ugly that they assumed the mind must lie elsewhere. Today those same skeletal silhouettes grow plump and brightly colored, courtesy of a variety of inserted genes encoding fluorescent molecules.
The experts are definitely getting closer: the last few decades have produced an explosion of new techniques for probing the blobby, unprepossessing brain in search of the thinking, feeling, suffering, scheming mind.

But the field remains technologically complicated, out of reach for the average nonscientist, and still defined by research so basic that the human connection, the usual “hook” by which abstruse science captures general interest, is often missing.

Carl Schoonover took this all as a challenge. Mr. Schoonover, 27, is midway through a Ph.D. program in neuroscience at Columbia, and thought he would try to find a different hook. He decided to draw the general reader into his subject with the sheer beauty of its images.

So he has compiled them into a glossy new art book. “Portraits of the Mind: Visualizing the Brain From Antiquity to the 21st Century,” newly published by Abrams, includes short essays by prominent neuroscientists and long captions by Mr. Schoonover — but its words take second place to the gorgeous imagery, from the first delicate depictions of neurons sketched in prim Victorian black and white to the giant Technicolor splashes the same structures make across 21st-century LED screens.

Scientists are routinely seduced by beauty. Mr. Schoonover knows this firsthand, as he acknowledged in an interview: for a while his wallet held snapshots not of friends or family, but of particularly attractive neurons. Sometimes the aesthetics of the image itself captivate. Sometimes the thrill is the magic of a dead-on fabulous technique for getting at elusive data.

Consider, for instance, a blurry little black-and-white photograph of a smiley-face icon, so fuzzy and ill-defined it looks like a parody of the Shroud of Turin. The picture is actually a miracle in its own right: the high-speed video camera that shot it was trained on the exposed brain of a monkey staring at a yellow smiley face. As the monkey looked at the face, blood vessels supplying nerve cells in the visual part of the monkey’s brain transiently swelled in exactly the same pattern. We can tell what was on the monkey’s mind by inspecting its brain. The picture forms a link, primitive but palpable, between corporeal and evanescent, between the body and the spirit. And behind the photo stretches a long history of inspired neuroscientific deductions and equally inspired mistakes, all aiming to illuminate just that link.

It’s only fitting that the story should be a visual one, for the visuals had the ancients fooled for millenniums. The brain was so irredeemably ugly that they assumed the mind was elsewhere.

Aristotle, for example, concluded that the brain’s moist coils served only to cool the heart, the obvious home of the rational soul. The anatomist Galen pointed out that all nerves led to the brain, but medieval philosophers figured that most of the important things happened within the elegantly curved fluid-filled ventricles deep inside.

Only when the long ban on dissection petered out in the Renaissance did the ventricles prove to be so much empty space — poke the brain around a little, and they collapse and disappear. The gelatinous brain moved into the spotlight, as resistant to study as a giant mass of tightly packed cold spaghetti.

The challenge was twofold: what did that neural pasta really look like, and how did it do what it did?

In 1873 the Italian scientist Camillo Golgi developed a black stain to highlight the micron-thin neural strands. Fifteen years later the Spanish scientist Santiago Ramón y Cajal, deploying the stain with virtuoso dexterity, presented the world for the first time with visible populations of individual neurons, looking for all the world like burnt scrub brush in a postapocalyptic Dalí landscape. The roots, or dendrites, of these elongated nerve cells gather information. The trunks, or axons, transmit it.

Now those same skeletal silhouettes glow plump and brightly colored, courtesy of a variety of inserted genes encoding fluorescent molecules. The most dramatic variation on these methods for highlighting neurons in living color, dubbed the Brainbow by its inventors, turns the brains of living mice into wild neon forests of branching trees.

The electrochemical circuitry that propels information around that forest, from nerve to nerve, has generated its own fabulous images.

One team of researchers harnessed the rabies virus, which has the unusual ability to travel upstream against the neural current. The virus moves from a leg bitten by a rabid dog up the long axons leading to the spinal cord, then jumps to dendrites of other nerves and travels up to the brain, where it causes horrific damage. Modifying the virus by a few genes and inserting it in mice, the researchers captured its path in a photograph, highlighting the long axon of the first nerve in brilliant magenta and then the tangle of dendrites of communicating nerves in yellow.

Meanwhile, the traffic in long groups of neurons all coursing together around the brain becomes visible with a variation on the standard scanning technique called diffusion M.R.I. Here the neurons do look just like pasta — angel hair, perhaps — slightly beaded, draped and purposeful. But if the structure is destroyed (by a stroke, for instance) the strands shatter into fragments, the information highway broken, upended as if by an earthquake.

In the book’s final essay, Joy Hirsch, a neuroimaging specialist at Columbia, sympathizes with readers who hate the idea that they — their essential selves, their likes and dislikes, their premonitions, biases and life decisions — are nothing but neural circuits.

“These cells and molecules, awash in various neurochemical cocktails in my basal ganglia, are presumably the basis for my love and attachment to my husband,” she writes. “Earlier in my academic journey I would have resisted this unavoidable fact of biology on the misguided rounds that a physical basis would diminish the grandeur and centrality of my choice of a life partner.”

Now, however, Dr. Hirsch says she joyfully embraces “the astonishing unity of the physical brain and the mind” for the potential it clearly holds for improving the lot of humankind. And furthermore, she doesn’t see that anyone has much choice about accepting it.

“People assumed for thousands of years that there must be something else,” the scientist Jonah Lehrer writes in the introduction. “And yet, there is nothing else: this is all we are.”

venerdì 19 novembre 2010


Participe da minha Palestra sobre as mentiras
24 de Novembro
Marriott Apartments
Rua Professor Azevedo 17
Vila Nova Conceiçao-Sao Paulo!

sabato 13 novembre 2010

Aprender a ler altera as redes neuronais do cérebro, diz pesquisa da Science

POR Lilian Ferreira
Do UOL Ciência e Saúde

Áreas ativadas do cérebro durante a leitura
O aprendizado da leitura altera redes no cérebro, interligando áreas de visão e fala e ativando zonas menos usadas. E a melhor resposta dos neurônios acontece tanto naqueles alfabetizados na infância quando na idade adulta. Esta foi a conclusão de um estudo feito por pesquisadores internacionais, com a participação da Rede Sarah, que será publicado na revista Science desta semana.

“Percebemos que uma área ativada por analfabetos ao ver faces e objetos do hemisfério esquerdo do cérebro era usada pelos que sabiam ler para reconhecer letras. A área da fala também teve sua resposta aumentada, mostrando ligação entre elas. E ao ver faces, os alfabetizados ainda ativavam a mesma área correspondente à visão do lado direito do cérebro”, explica Lucia Willadino Braga, coordenadora do estudo e pesquisadora do Centro Internacional de Neurociências da Rede Sarah.

Assim, não é que o cérebro se modifique ao aprender a leitura, mas ele passa a fazer novas ligações e a usar áreas antes negligenciadas ou com funções diferentes.

O estudo mediu, através de ressonância magnética funcional, a atividade cerebral de 63 adultos voluntários com níveis variados de alfabetização, enquanto uma bateria de estímulos lhes era apresentadas como frases faladas e escritas, palavras e falsas palavras faladas, rostos, casas, objetos e tabuleiros. Eram 10 analfabetos, 22 pessoas alfabetizadas na idade adulta e 31 pessoas escolarizadas desde a infância. A pesquisa foi realizada simultaneamente com portugueses e brasileiros.

Leitura e fala

A leitura aumenta as respostas à linguagem falada no córtex auditivo, em uma área relacionada à codificação dos fonemas. Esse resultado corresponde à constatação de que os analfabetos não conseguem realizar jogos de linguagem, tais como a deleção do primeiro som de uma palavra (Banana → anana).

A pesquisa também mostrou a comunicação bidirecional entre as redes da linguagem falada e escrita: para um bom leitor, ver uma frase escrita ativa a totalidade das áreas da linguagem falada e, ao escutar uma palavra falada, a pessoa tem reativado rapidamente o seu código ortográfico nas áreas visuais. Nos indivíduos que não aprenderam a ler, o tratamento da linguagem é menos flexível e estritamente limitado à modalidade auditiva.

Segundo Braga, a diferença entre os que aprenderam a ler na infância e aqueles alfabetizados na fase adulta é que os primeiros possuem mais redes e, por treino de leitura, conseguem ler mais palavras por minuto. “Quanto mais estimulado pela leitura, mais complexas são as redes neurais”, conta.

A neurocientista ainda ressalta que a maioria das pesquisas com ressonância magnética funcional é realizada com cérebro educado e que sua organização, na ausência de educação, constitui um território amplamente inexplorado.

giovedì 4 novembre 2010

Language and toolmaking evolved together, say researchers


Evolutionary advance saw stone-age humans master the art of hand-toolmaking and paved the way for language to develop

Stone-age humans mastered the art of elegant hand-toolmaking in an evolutionary advance that boosted their brain power and potentially paved the way for language, researchers say.

The design of stone tools changed dramatically in human pre-history, beginning more than two million years ago with sharp but primitive stone flakes, and culminating in exquisite, finely honed hand axes 500,000 years ago.

The development of sophisticated stone tools, including sturdy cutting and sawing edges, is considered a key moment in human evolution, as it set the stage for better nutrition and advanced social behaviours, such as the division of labour and group hunting.

"There has been a long discussion in the archaeology community about why it took so long to make more complex stone tools. Did we simply lack the manual dexterity, or were we just not smart enough to think about better techniques?" said Aldo Faisal, a neuroscientist at Imperial College London.

Faisal's team investigated the complexity of hand movements used by an experienced craftsman while he made replicas of simple and then more complex stone tools. Bruce Bradley, an archaeologist at Exeter University, wore a glove fitted with electronic sensors while he chipped away at stones to make a razor-sharp flake and then a more sophisticated hand axe.

The results showed that the movements needed to make a hand axe were no more difficult than those used to make a primitive stone flake, suggesting early humans were limited by brain power rather than manual dexterity.

Early humans were adept at making stone flakes, but these were so thin they were liable to break while being used. The movements needed to make advanced tools were no more difficult, but they had to be executed more intelligently, to produce a tool that had a fat, sturdy body with a sharp cutting edge.

The oldest and simplest stone tools, known as Oldowan flakes, were uncovered alongside the fossilised remains of Homo habilis, a forerunner of modern humans, in the Olduvai Gorge in Tanzania. Stone hand axes have been uncovered next to bones of Homo erectus, the ancient human species that led the migration out of Africa. Hand axes are usually worked symmetrically on both sides into a teardrop shape.

Brain scans of modern stone-tool makers show that key areas in the brain's right hemisphere become more active when they switch from making stone flakes to more advanced tools. Intriguingly, some of these brain regions are involved in language processing.

"The advance from crude stone tools to elegant handheld axes was a massive technological leap for our early human ancestors. Handheld axes were a more useful tool for defence, hunting and routine work," said Faisal, whose study appears in the journal PLoS ONE. "Our study reinforces the idea that toolmaking and language evolved together as both required more complex thought, making the end of the lower paleolithic a pivotal time in our history. After this period, early humans left Africa and began to colonise other parts of the world."

martedì 2 novembre 2010

Estudo diz por que orientais são "iguais"


Ocidentais têm essa impressão porque o cérebro humano "dá bug" ao tentar reconhecer faces de outra etnia

Para orientais, difícil é diferenciar os europeus; as bases biológicas dessa dificuldade ainda eram desconhecidas


Não, os japoneses não são todos iguais. O que acontece, mostraram agora os cientistas, é que o "software" de reconhecimento facial do cérebro tem as suas limitações, e uma delas é patinar sempre que se depara com um rosto de uma etnia diferente.
Os pesquisadores selecionaram mais de 20 voluntários, metade de Europa e metade da Ásia. Mostraram a eles faces genéricas de orientais e ocidentais. Enquanto isso, observavam a sua atividade cerebral.
Perceberam que os voluntários decoravam com facilidade rostos de gente da mesma etnia que eles. Mas quando um europeu começava a observar faces orientais, logo se perdia e já não sabia dizer se um novo rosto era inédito ou não -e vice-versa.
Ao observar o que estava acontecendo no cérebro do coitado do europeu, perdido tentando lembrar se aquele chinês não era o mesmo que já tinha aparecido lá no começo, os cientistas notaram um significativo aumento na sua atividade neural.
É como se o cérebro do voluntário estivesse exigindo mais do "processador", sendo forçado a trabalhar mais para tentar encontrar alguma forma de conseguir reconhecer aquele sujeito na tela. Fosse um computador, o cérebro estaria esquentando. Com frequência, o esfoço extra acaba sendo em vão.
Esse fenômeno é perceptível especialmente em algumas áreas do cérebro ligadas ao reconhecimento facial, como o córtex extra-estriado.
Assim, um japonês que nunca saiu do seu país, ao desembarcar, digamos, na Alemanha, vai achar todos aqueles loiros muito parecidos e se questionar como é que eles conseguem saber quem é quem no dia-a-dia.
A explicação evolutiva mais simples para esse bug cerebral passa pelo fato de que passear pelo mundo fazendo amigos é coisa recente. Por dezenas de milhares de anos, encontros com etnias diferentes eram muito raros. Só era necessário identificar gente parecida, e o cérebro se moldou para isso.

Roberto Caldara, neurocientista italiano-da Universidade de Glasgow (Escócia) e autor do trabalho publicado na revista científica "PNAS", diz que é interessante notar como esse cérebro limitado se adapta às grandes cidades cosmopolitas do presente, com gente de todo tipo nas ruas.
"Se você for europeu, mas morar, digamos, em um bairro com muitos chineses, você vai ver muitos rostos orientais todos os dias. Mas, exceto se você tiver treinado seu cérebro para reconhecê-los no nível individual, tendo vários amigos chineses e sabendo diferenciá-los, você vai continuar achando todos muito parecidos."
Isso vale, então, diz, para São Paulo: para parar de confundir orientais (e irritá-los chamando, por exemplo, coreano de japonês), é necessário se entrosar socialmente- só passear no bairro da Liberdade não adianta.