What Can a Cell Remember? | Quanta Magazine

If an intracellular mechanism for memory exists in brainless, unicellular organisms, then it’s possible we inherited some form of it, given the advantages it presents. All eukaryotic cells, including our own, trace their evolutionary origins to a free-living ancestor. That legacy echoes in our every cell, yoking our fates to the vast unicellular realm, where creatures such as protozoans navigate threats, seek succor and sense their way from life to death.

From the perspective of the cell, or any other living system that shows the spacing effect, spaced information is evidence of a fairly consistent, slow-moving environment: a steady world. Massed information, on the other hand — a singular burst of chemicals or an all-night cram session — might represent a fluky event in a more chaotic environment. “If the world is changing really fast, you should forget things [more easily], because the things that you learned are going to have a shorter shelf life,” Gershman said. “They’re not going to be as useful later on, because the world will have changed.” These dynamics are as relevant to a cell’s existence as they are to ours.

In neuroscience, Kukushkin writes, the most common definition of memory is that it’s what remains after experience to change future behavior. This is a behavioral definition; the only way to measure it is to observe that future behavior. Think of S. roeselii snapping back into its holdfast, or a lab rat freezing up at the sight of an electrified maze it’s tangled with before. In these cases, how an organism reacts is a clue that prior experience left a lingering trace.

Perhaps a definition of memory should extend beyond behavior to encompass more records of the past. A vaccination is a kind of memory. So is a scar, a child, a book. “If you make a footprint, it’s a memory,” Gershman said. An interpretation of memory as a physical event — as a mark made on the world, or on the self — would encompass the biochemical changes that occur within a cell. “Biological systems have evolved to harness those physical processes that retain information and use them for their own purposes,” Gershman said.
— Read on www.quantamagazine.org/what-can-a-cell-remember-20250730/