According to new research, individual cells appear to be able to carry out a complex learning that is often associated with the entire nervous system, from oozing amoeba to our body's own building blocks.

Jeremy Gunawardena, a biologist at Harvard Medical School, said: "This discovery opens up an exciting new mystery for us: How do cells without a brain process something so complex? ”

The learning form in question is known as "habituation" and occurs when the response to an unrewarded stimulus decreases with increasing repetitions. For example, it describes why wild animals may become accustomed to human presence, or why unusual smells in rooms become less noticeable over time.

Lina Eckert, a neurobiologist at the Max Planck Institute, and her colleagues used computer models to rapidly test molecular networks in mammalian cells and single-celled organisms called ciliates. They found four molecular networks, each with a dual-response system, one of which dissipated much more slowly than the other.

This ability to respond differently to impulses is habituation. Slow-dissipating responses can hinder short-term responses to impulses, effectively adapting cells to stimuli. Once the slow reaction subsides and the fast reaction returns, the reaction is triggered again with its original intensity.

"We think it could be a kind of 'memory' at the cellular level, allowing the cell to respond both immediately and influence future responses," explains Rosa Martinez, a biologist at the Center for Genome Regulation.

The team has not confirmed their findings in living cells, but habituation has been confirmed in ciliates.

"Our approach can help us prioritize which experiments are most likely to yield valuable results, save time and resources, and lead to new breakthroughs," says Rosa Martinez. ”

If the researchers' findings are correct, and the identified molecular networks are confirmed to be a form of cellular memory, understanding how they work could reveal ways to prevent our immune system from adapting to the presence of cancer cells.

"It's akin to an illusion," Gunawardena explains. "If we know how these false perceptions are encoded in immune cells, we might be able to redesign them so that immune cells start to sense their environment correctly, tumors become visibly malignant, and then they start working. Now it's just a fantasy, but it's a direction I'm willing to explore. ”

This isn't the only way to learn that has been discovered in cells recently. Another research team recently discovered that cells may also have the ability to learn through repetition.

"The question of learning outside of animals with brains has been fraught with controversy, and from a historical perspective, it has often been both ideological and scientific," Eckert and his team said.

"Because single-celled organisms have to solve the same problems of survival as any living organism...... It seems plausible that evolution has provided it with a basic form of learning similar to that used by animals. ”

The study was published in the journal Current Biology.