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After Karim Nader Upended the Science of Memory, He Started to Lose His Own

How the esteemed neuroscientist is grappling with a life-changing diagnosis

DECEMBER 2026 / SCIENCE

After Karim Nader Upended the Science of Memory, He Started to Lose His Own

How the esteemed neuroscientist is grappling with a life-changing diagnosis

ILLUSTRATION BY JULIETA CABALLERO

Published 6:30, OCTOBER 15, 2026

KARIM NADER SIPPED from a Coke can as he strode across the front of the lecture hall in a long coat, one ear pierced, tossing out questions and calling on students at random to answer them. “What do you think it would be like if you couldn’t forget anything—if you remembered every single detail of your life?” It was around 2007: I was in my second or third year of undergrad at McGill University, and Nader was teaching a class on his work in memory research.

He called on me for my answer. I sputtered out something about how it would feel overwhelming, if not impossible, to go about one’s day with all those memories crowding the mind. “That’s right, it would,” he said, and went on to talk about why we forget.

I’ve since learned that experiencing stress, even a mild form of it, might help some memories stick, which might be why I remember the encounter so vividly. Or, at least, I remember a version of it. The details are probably a bit off, embellished here and there, because science tells us that long-term memories aren’t fixed, flawless renditions of the past. And when I say science, I mean Nader.

In 2000, when he was a thirty-three-year-old post-doctoral researcher at New York University, Nader co-published a study in the journal Nature that blew up the field of memory research. Testing fear responses in rats, Nader and a colleague, Glenn Schafe, showed that when memories are recalled, they have to be reassembled, which renders them unstable for a brief period and opens them up to editing and error. In the lab, Nader and Schafe had demonstrated what some neuroscientists had suspected and psychologists had been arguing for decades: remembering is a constructive, even creative, endeavour.

The finding challenged the central dogma in neuroscience at the time, which held that long-term memories are consolidated once through the formation and strengthening of connections between neurons. Nader, Schafe, and their supervisor, Joseph LeDoux, suggested in a follow-up paper later that year that what is known as memory reconsolidation could perhaps be harnessed to develop clinical treatments for people with post-traumatic stress disorder or related conditions.

In the years after that undergrad lecture, I kept thinking back to Nader’s research. As I learned about how trauma can shape or shatter lives, sometimes for generations, I wondered whatever happened to his work on reconsolidation therapy. Every once in a while, I’d google him.

Then, a few years ago, I came across a news story from 2017 mentioning he’d enrolled in a clinical trial for Huntington’s disease, which the article described as “Alzheimer’s, Parkinson’s and ALS all rolled into one debilitating condition.” I found a post online about a symposium at the Montreal Neurological Institute Hospital that Nader’s colleagues held in his honour in 2022, along with a brief interview about his research.

The following year, the journal Brain Research Bulletin dedicated an issue to Nader’s work and legacy. In the editorial note, Paul Frankland, a senior scientist in the neurosciences and mental health program at the SickKids Research Institute in Toronto and one of Nader’s closest friends, credits that 2000 study with triggering a paradigm shift in memory research. In another essay, LeDoux describes Nader as a “force of nature.”

Nader had known for much of his adult life that he had Huntington’s, a hereditary neurological illness that typically leads to cognitive decline and loss of motor control, among other symptoms. Though he’s still affiliated with McGill, and attends conferences when he can, Nader doesn’t teach or work in his lab. “It’s still him,” says Sheena Josselyn, also a senior scientist at SickKids and a professor at the University of Toronto. “But it’s harder to get at him now.”

Last year, I met Nader at his mother’s house in Toronto. He was visiting from Montreal, along with his partner, Gentiana Sadikaj, and his sister, Marion. As I introduced myself and we sat down, Nader reached out a hand to shake mine. The gesture must have taken enormous effort, as his every movement was interrupted by uncontrollable, jolting muscle contortions. When he spoke, it was in clipped, but clear enough, bursts.

I had gone into the interview primed to ask a few open-ended questions and let the conversation turn where it may, ideally arriving at any fresh insights the illness had opened up for him about his work. How did the prospect of memory loss colour his own views on remembering and forgetting? Surely, I thought, he’d earned the licence to riff a little, to get philosophical.

But he didn’t seem interested in going there. Some of my questions he parried away with punch lines. When I asked if he sensed most people understand that their memories are imperfect, he deadpanned: “The only one who refuses to budge is my mom.”

FRANKLAND AND JOSSELYN, now married, met Nader when they were all working on their PhDs at the University of Toronto, in the early 1990s. Though they weren’t yet friends, they couldn’t not know Nader: he was self-assured, outgoing, and unintimidated by their professors, even challenging them in lectures and once storming out in protest. “He was comfortable with who he was,” recalls Josselyn. “He’d wear obnoxiously flashy shirts. He never had any sense of self-consciousness.”

The trio grew close when Frankland and Nader, and later Josselyn, moved to the United States. Nader was at New York University, Josselyn did her postdoc at Yale University, and Frankland joined a lab at Cold Spring Harbor Laboratory on Long Island, and they’d get together in Manhattan at least once a week to play pool and talk about their research. “There was a lot of writing on the back of napkins in bars,” says Josselyn. One time, when Josselyn and Frankland were waiting for Nader at their usual bar, they spotted a man from........

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