T

hree neuroscientists whose research overturned decades-old notions about how and whether the brain can change in response to experience have won a $1 million Kavli Prize in Neuroscience, the Norwegian Academy of Science and Letters announced on Thursday.

In an event live-streamed from Oslo to the World Science Festival in New York City, academy president Dr. Ole Sejersted said that Michael Merzenich of the University of California, San Francisco, Carla Shatz of Stanford University, and Eve Marder of Brandeis University were being honored for discovering “mechanisms that allow experience and neural activity to remodel brain function.”

The discoveries have led to the development of cochlear implants for hearing loss and to therapies that exploit the brain’s power of “neuroplasticity” to recover from stroke, depression, Tourette syndrome, and other conditions — all without the use of drugs.

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The winners’ research also helped forge a revolution in neuroscience.

Contrary to longstanding assumptions that the brain was “hard-wired,” these three neuroscientists showed, beginning in the 1980s, that the experiences people have — and even the thoughts they think — can act back on the physical structure of the brain to change it.

For instance, intense therapy to move an arm impaired by a stroke can alter the brain in a way that restores movement. And mental practice of the movements used in sports (such as tennis serves and golf swings), and of playing an instrument like the piano, can alter the brain and strengthen circuits that underlie proficiency nearly as much as actual, physical practice does.

Neuronal activity, generated either by what we do or what we think, literally sculpts the connections between neurons and thereby changes the structure and function of circuits, the Kavli laureates demonstrated.

Before their pioneering discoveries, the century-old conventional wisdom in neuroscience held that the adult brain is essentially fixed in structure and function. Regions that moved the right pinky or the left leg would always do that and nothing else; the number and strength of connections between different regions, which determine things like depression, were long thought immutable.

That dogma was so strong that when Merzenich’s experiments in monkeys showed that the animals’ experiences could change their “brain maps” — which regions moved or received the sense of touch from which parts of the body — experts didn’t believe him.

Merzenich also discovered that the brain’s map of sound frequencies, in which one cortical spot handles middle C and another the E flat above that and so on, can be changed so that more of the brain is given over to one frequency than another. That became the basis for electronic cochlear implants, which remap the brain so it can hear again.

And Merzenich’s discovery that paying close attention to experiences is required for neuroplasticity led to brain-training programs developed by a company, Scientific Learning, that he helped found to treat dyslexia as well as the memory losses and other problems that come with age.

Shatz made her mark in studies of brains at the other end of the lifespan: those still developing before birth.

She focused on the circuit connecting neurons from the retina to those in the visual cortex. She showed that, rather than wending their way according to a genetic script and forming predetermined connections, as had been assumed, retinal neurons hook up in a pattern based on their electrical activity before birth. Spontaneous waves of activity, she found, sweep across the retina, causing some far-flung neurons to fire in close sequence.

The principle that “neurons that fire together, wire together” explained the formation of key circuits in the developing brain, she discovered.

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Marder studied the simple circuits of lobsters and crabs to show how neural circuits keep a delicate balance between flexibility and stability. Also challenging the “hard-wired” dogma, she showed that brain chemicals called neuromodulators can subtly affect the output of neural circuits without changing their structure; that allows the same circuit to dial behaviors such as walking, breathing, and swimming up or down.

The Kavli Prize is administered every two years by the Norwegian Academy, Norway’s Ministry of Education and Research, and the Kavli Foundation, which is headquartered in Oxnard, Calif. It is named after inventor and real-estate investor Fred Kavli, a Norwegian-American who died in 2013.

Prizes were also announced Thursday in astrophysics (for work leading to the detection of gravitational waves) and in nanoscience (for the invention of an advanced form of imaging called atomic force microscopy).

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