We tend to celebrate memory, not forgetting; however, forgetting may be what keeps our minds flexible enough to adapt and learn.
At Flinders University, a team of researchers has shown that the same brain chemical that helps us learn – dopamine – also helps us forget.
“We often think of forgetting as a failure, but it’s actually essential,” said lead author Dr. Yee Lian Chew, a senior lecturer at Flinders University.
Why forgetting is productive
Forgetting sounds like a defect; however, researchers are now treating it as an active, adaptive process that keeps brains adaptable. Active forgetting removes outdated or irrelevant information, allowing neural circuits to encode new, useful signals. Experimental and theoretical work argue that this is an advantage: a system that never prunes memories would be slower, less flexible and more error-prone.
“If the environment changes, the brain must adapt to a new reality. Therefore, forgetting aspects of the old environment no longer relevant to the new is critical for survival,” Chew told Technology Networks.
Previous work in fruit flies found that the neurotransmitter dopamine, known for playing a role in learning, may also be just as important in the process of forgetting.
The Flinders team turned to a tiny, transparent worm to probe how the brain forgets. The nematode Caenorhabditis elegans is a millimeter long, with around 300 neurons, but it shares many of the same memory genes as humans. Its simplicity makes it an ideal model for pinpointing how specific brain chemicals shape behavior.
The new study aimed to determine how dopamine controls the act of forgetting and whether the same molecular logic might underlie memory flexibility in larger brains.
Dopamine-driven forgetting
The researchers trained worms to link the smell of butanone with food – a simple form of associative learning. After training, the worms were tested immediately and again over the next two hours to see how long they would remember that the odor signaled food.
The team compared normal worms with several genetically modified strains. Some could not make dopamine (cat-2 mutants), others could make it but had trouble recycling it (dat-1 mutants) and others lacked dopamine receptors (dop-1, dop-2 and dop-3). These differences allowed the team to isolate which parts of the dopamine system are needed for forgetting.