The Nobel laureate’s scientific journey had its beginnings in 1930s Vienna. During his childhood there, he witnessed a terrifying transformation in his hometown. Neighbors who once had been kind and friendly turned hateful and violent, twisted by the rhetoric of the Nazi Party and the rise of Adolf Hitler. The experience, and the subsequent genocide that his Jewish family escaped by coming to the United States, left the young Kandel with a burning question: “How could civilized people become so brutal and vicious?”

Hoping to better understand why people act the way they do, Dr. Kandel turned to psychiatry. He studied Freud and earned a medical degree to become a psychoanalyst. Then a course he took at New York University inspired him to focus on the physical organ responsible for our thoughts: the brain itself. He began searching for the origins of behavior in biology, in the cells and chemicals that make up the brain, at a time when relatively few were doing so.

This pioneering spirit paid off. Dr. Kandel’s research has laid part of the early foundations for our current understanding of memory. His name appears on more than 500 research papers, and he has been recognized with some of the world’s top scientific awards, from the Nobel Prize to the Wolf Prize. He is one of the best-known neuroscientists on the planet, thanks in part to the half a dozen books he has written about the brain, including The Disordered Mind: What Unusual Brains Tell Us About Ourselves.

His search for memory began in the hippocampus, a Latin word meaning “seahorse” (referring to this brain region’s shape). Neuropsychologist Brenda Milner had shown that this part of the brain was important for memory formation. Kandel and Columbia University professor W. Alden Spencer were the first to measure its electrical activity, doing so in the brains of mice. They learned something about how the cells they monitored, called neurons, worked, but they didn’t learn much about how memory works. The brains of mice were just too complicated.

It was an important lesson for the fledgling researcher.

“As a scientist, you must select the appropriate system for the question you want to answer,” says Dr. Kandel, who is now Professor Emeritus of Physiology and Cellular Biophysics, Psychiatry, Biochemistry and Molecular Biophysics, and Neuroscience at Columbia. “We started looking for a simpler system that could tell us something about behavior.”

Others had studied squid, which have giant axons that are easy to work with. Dr. Kandel looked into flies, worms and even lobsters, before settling on a type of marine snail known as Aplysia. This large snail has large neurons. Moreover, its nervous system contains only about 20,000 brain cells, as compared to the estimated almost 100 billion in your brain.

Inspired by Ivan Pavlov’s experiments with dogs, Dr. Kandel sought to understand a simple behavior in his Aplysia. He poked the snails and noticed that they contracted their sensitive gills defensively. After repeated pokes, though, the animals stopped responding; they had learned they were in no danger. Then Dr. Kandel gave the creatures both a poke and a mild but unpleasant electrical shock. The Aplysia changed their behavior again. Subsequent pokes triggered gill withdrawals, even without a shock. They had learned to associate the poke with the shock.

Dr. Kandel and his colleagues monitored what happened in the neurons during this learning, as the snails remembered their experiences. The scientists found differences in the strength of the connections, aka synapses, between the cells.

“At that time there were many ideas about how learning occurs,” says Dr. Kandel, who was a Senior Investigator at the Howard Hughes Medical Institute from 1984 to 2022. “We were able to show that synapses in the brain can be modified by learning.”

Building on this groundbreaking work, Dr. Kandel has studied the molecules and genes that help the brain turn short-term memories into long-term memories and those that suppress memory formation altogether. He has investigated the roots of brain disease and proposed new frameworks for bringing together psychiatry and biology. He and his collaborators have revealed important differences between normal memory loss due to ageing and that due to Alzheimer’s disease, and have created new genetically modified mice that could be useful for studying conditions like schizophrenia. One surprising piece of research suggested that the long-term memories in the brain are maintained by proteins similar to those that cause mad cow disease. Another revealed the importance for memory of a bone hormone released when we walk.

One of the foremost experts on memory, Dr. Kandel cofounded Columbia University’s Center for Neurobiology and Behavior in 1975, the university’s first neuroscience department. The bowtie aficionado also cofounded Columbia’s Zuckerman Institute and literally wrote the book on neuroscience: Principles of Neural Science, used in university classrooms. And his keen interest in art inspired two books that explore how the brain reacts to art.

Dr. Kandel enjoyed his work immensely and wants us all to know something: “There’s life after a Nobel Prize.”

He also wants everyone to know how important his wife, Denise Bystryn Kandel, has been to his career. A professor at the Columbia Mailman School of Public Health, she developed the gateway hypothesis for drug addiction and has been a key voice and a colleague in his research.

“She is one of the reasons I came to Columbia,” says Dr. Kandel.