'It's kind of the holy grail of what is memory': Neuroscientist Steve Ramirez studies the physical basis of memory in a quest to manipulate it

In 2013, MIT neuroscientists Steve Ramirez and Xu Liu published a paper detailing how they had created false memories in mice.

They'd used optogenetics — where cells' activity is manipulated using light — to plant a fearful memory in the brain and then reactivate this memory with these pulses of light.

The breakthrough helped to propel research in the field by showing that memories can be artificially constructed.

The initial experiments involved using a protein to tag brain cells in the hippocampus (a key memory center in the brain) that were active during the formation of a fearful memory.

They then reactivated these "fear memory-bearing cells" while the mice were perfectly safe.

The first four mice showed no response, but the fifth froze in fear.

After analyzing the fifth mouse's brain, it turned out they had placed the protein in a slightly different location of the hippocampus to the others by accident — and inadvertently found the exact spot where the memory was stored — and that it could be manipulated and controlled.

In his book " How to Change a Memory: One Neuroscientist's Quest to Alter the Past " (Princeton University Press, 2025), Ramirez , now an associate professor at Boston University's Center for Memory and Brain,explores fundamental questions about memory: What is it, and can we manipulate it? He uses his personal experiences ‪—‬ including with loss, PTSD and addiction — to probe these ideas, asking whether this line of research could open new paths to treatments.

He conceptualizes a world where memories could be manipulated to help ease a person's PTSD, or guard against dementia.

Live Science spoke with Ramirez about the book, the future of memory research, the ethics and implications for treating disease, and our brains' extraordinary power to recall our past.

"How to Change a Memory" has been short-listed for the 2026 Royal Society Trivedi Science Book Prize .

"How to Change a Memory" excerpt: 'As if a shudder ran from its brain to its body': The neuroscientists that learned to control memories in rodents Hannah Osborne: In the book, you reflect on your and Xu's major 2013 paper, noting that it was initially the result of a botched surgery in a single mouse.

What if that little mistake hadn't happened? Steve Ramirez: If we hadn't accidentally botched the surgery, I'd like to think we still would have gotten there, because what would have happened was that we would have done all the surgeries correctly, we would have hit the wrong spot, and everything would have been a negative result.

And then, we would have said, "Maybe this is the wrong area to try to activate a memory." Now, where we would go next, I don't know.