Every memory begins with tiny changes inside the brain. A discovery that helped explain those changes has earned neuroscientist Oswald Steward one of science’s highest honors.

Steward received the 2026 Kavli Prize in Neuroscience, a USD 1 million award and one of science’s most prestigious awards, for research that transformed scientists’ understanding of how the brain learns and stores memories. Steward and his colleagues won the prize for discovering that neurons, the cells that carry information through the brain and nervous system, can manufacture proteins near synapses, the connections where brain cells communicate.

The finding has reshaped neuroscience and could eventually lead to new treatments for neurological disorders.

“It was not a conclusion that was really in line with what other people were thinking at the time,” Steward told IBM Think in an interview. “We sort of stuck to it, dog to a bone, couldn’t let go.”

Steward shares the prize with Christine Holt, Kelsey Martin and Erin Schuman for discoveries that established the importance of local protein synthesis, the process by which cells build proteins, within neurons. Scientists now regard the process as fundamental to learning, memory and brain plasticity, the brain’s ability to reorganize itself in response to experience.

The discovery dates to research Steward began more than four decades ago, when scientists still believed proteins were manufactured primarily in a neuron’s cell body.

“It is the thrill of discovery,” he said. “There’s just something about it that you can’t really explain or find in any other situation.”

The discovery hidden inside a neuron

Much of modern neuroscience rests on understanding neurons, the specialized cells that transmit information throughout the nervous system. A single neuron can extend extraordinary distances while maintaining thousands of synapses, the junctions where nerve cells exchange signals.

Scientists long believed proteins needed by neurons originated primarily in the cell body before traveling outward to distant parts of the cell. Those proteins help neurons maintain synapses and strengthen or modify them in response to experience, a process central to learning and memory. Steward had no intention of challenging that view. He was studying how the brain formed new connections after injury.

Steward and his colleagues used radioactive amino acids, the building blocks of proteins, to track protein production in neurons. They expected to see increased activity in neuronal cell bodies. Instead, the signals appeared elsewhere. Curious about the result, Steward turned to electron microscopy, a technique that uses beams of electrons to produce highly detailed images of cells.

What appeared under the microscope changed the direction of his career.

“What we saw was that there were these incredibly beautiful clusters of polyribosomes at spine synapses,” he said. Ribosomes are tiny structures inside cells that manufacture proteins. Synapses are the communication points where neurons pass signals to one another.

The implications struck him immediately. The observation hinted at a new explanation for how neurons could support changes at individual synapses.

“I know it sounds corny, but that was when the idea came to me,” he said. “‘Oh my gosh, this is the missing link.’”

Solving a mystery of memory

The discovery helped explain a problem that neuroscientists had struggled with for years.

Learning and memory depend on changes at specific synapses. Scientists knew those changes required new proteins. But they couldn’t easily explain how a neuron could direct those proteins to one particular connection among thousands spread across an elaborate network of branches.

The challenge becomes obvious, Steward said, once researchers consider the physical scale of a neuron. A single cell can maintain thousands of synapses distributed across a complex network of branches.

“If you tried to make the proteins in the cell body and transport them out to the synapse, there’d be this huge traffic jam,” he said.

The answer involved messenger RNA, molecules that carry genetic instructions for building proteins. Rather than transporting proteins from the cell body, neurons can send messenger RNA to individual synapses and manufacture proteins locally when needed.

Researchers now view that process as a fundamental mechanism behind synaptic plasticity, the ability of connections between neurons to strengthen or weaken over time. The discovery provided a new framework for understanding how memories form and persist inside the brain.

From memory to medicine

What began as a basic science discovery now influences research into a wide range of neurological disorders.

Defects in protein production at synapses may help drive a range of neurological disorders. Scientists are investigating links to conditions including Fragile X syndrome, an inherited disorder that affects learning and development, and Alzheimer’s disease, in which nerve cells progressively lose function and die.

Fragile X syndrome has drawn particular attention because researchers already know that the disorder stems from mutations involving a protein called Fragile X messenger ribonucleoprotein which interacts closely with messenger RNA and protein production at synapses.

Researchers still don’t fully understand how those molecular changes translate into symptoms, or when interventions might prove most effective. However, Steward believes that deeper understanding will eventually produce new treatment opportunities.

“Maybe I’m just hopelessly optimistic, but I really believe that as we begin to understand the molecular basis of these diseases and disorders, new treatments will appear,” he said.

Alzheimer’s disease, for example, has long been associated with plaques, tangles and dying neurons. Steward said that researchers may need to pay closer attention to what happens earlier in the disease process.

“One of the first things that happens is actually synapse loss,” he said, adding that understanding how synapses survive, adapt and repair themselves could eventually reveal new ways to slow neurological decline.

Looking beyond AI

Yet, even after decades of studying how the brain learns and changes, Steward says one mystery remains unsolved: the sudden spark behind original thinking. The award arrives as AI systems demonstrate increasingly sophisticated reasoning and researchers debate whether machines could eventually rival humans in scientific discovery. Steward remains skeptical.

Steward’s work focuses on the biological mechanisms that allow the brain to learn and adapt. Asked what those discoveries might mean for the future of artificial intelligence, he said AI remains better suited to processing information than generating genuinely original insights.

At the same time, he said that he believes neuroscience still holds lessons that computing has yet to absorb. While many technologists hope AI will unlock the mysteries of intelligence, Steward suspects the deeper insights will flow in the opposite direction.

“I think that it’s much more likely that understanding the brain will create new things about artificial intelligence than the opposite,” he said.

His reasoning reflects decades spent studying biological intelligence at the molecular level. Moreover, months of remote work during the COVID pandemic reinforced a lesson he believes scientists sometimes overlook: scientific breakthroughs depend heavily on interactions with other people.

“We are social beings,” he said.

Mysteries beyond memory

Many of neuroscience’s greatest mysteries have been unlocked by decades of research. Scientists now know far more about neurons, synapses and the molecular machinery that supports learning than they did when Steward began his career.

Yet one question continues to resist explanation.

Even after a lifetime spent studying the brain, Steward says the deepest mystery remains the moment when a new idea appears seemingly from nowhere. Scientists can identify cells, molecules and circuits involved in cognition. They still struggle to explain the spark that transforms information into insight.

“That’s one of the most important things the brain does,” he said. “This emergent thing that comes not in any particularly logical way, but just kind of pops out.”

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