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.”

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