In a conversation for The Guardian’s science podcast, Steve Ramirez, an associate professor of psychological and brain sciences at Boston University, described a body of work in which researchers have been able to identify the physical traces of memories in rodent brains and then activate or suppress those traces experimentally. Ramirez, whose book How to Change a Memory was shortlisted for the Royal Society Trivedi science book prize, discussed both the methods used in the laboratory and the broader implications of the findings.
Research on memory engrams
Ramirez explained how neuroscientists have moved beyond abstract theories of memory to experiments that pinpoint where particular memories are encoded in the brains of animals. In these studies, teams locate networks of neurons associated with a given memory — often called engrams — and then manipulate those networks to test whether reactivating or disrupting them changes the animal’s recollection or behaviour.
Triggering and removing memories
According to Ramirez’s account, scientists have not only been able to reactivate memories by stimulating the identified neural networks, but in some cases have also suppressed or erased memories by interfering with those same circuits. He described these results as demonstrating a causal link between specific neural ensembles and the content of memory, allowing researchers to induce, modify or attenuate recollections in controlled experimental settings.
Potential human applications and ethical questions
Ramirez said the work points to possible future applications for people, including new ways to treat psychiatric conditions that involve distressing memories, and approaches to memory disorders. He also noted the ethical and practical challenges ahead: translating findings from rodents to humans is complex, and deliberate manipulation of human memory raises profound moral and societal questions that would need careful consideration.
A growing field with wide interest
The interview and Ramirez’s book present the research as part of a rapidly developing field in neuroscience that is reshaping how scientists think about the physical basis of memory. While the experiments so far have been conducted in animals, Ramirez emphasised that the scientific advances open lines of inquiry about memory’s mechanisms and the potential for therapeutic innovation, even as they prompt debate about limits and safeguards.