If files on your computer suddenly vanished after a while, you'd be in line for a new one pretty quickly – and yet, that's basically what our brains do all the time. From misremembering facts in an exam that you spent all night cramming for, to losing the keys that were just in your hand a minute ago, forgetting is a frustrating experience. But a new paper suggests that when it comes to human memory, forgetting things may be just as important as remembering.
The new work is a review paper, taking a wider snapshot of the recent studies of the brain mechanisms involved in memory. But there are two sides to that coin: remembering (persistence) and forgetting (transience). Forgetting isn't just a failure to recall information, but an active process that helps the brain as a whole make decisions more efficiently.
"It's important that the brain forgets irrelevant details and instead focuses on the stuff that's going to help make decisions in the real world," says Blake Richards, one of the paper's authors. "If you're trying to navigate the world and your brain is constantly bringing up multiple conflicting memories, that makes it harder for you to make an informed decision."
Rather than just holding onto everything like a sponge, the brain works better as an information filter. Unused or irrelevant fragments can be cleared away like running a disk cleanup on a computer, and we're left with the general gist of memories rather than every tiny detail. That's why you can remember your high school math teacher, but not every answer to every test you took.
Balancing persistence and transience helps us make better memory-based decisions in a few ways. Outdated information is let go in favor of what's more current, and generalizing the memories into core ideas allows us to apply them to more situations in the future.
As for how the brain actually does this, the researchers found a few mechanisms are at play. Synaptic connections between neurons can weaken or be eliminated over time, and as new neurons develop, they rewire the circuits in the hippocampus, overwriting existing memories. This could be particularly useful in a fast-paced environment, where new information is constantly flooding in and there's no point holding onto older details.
The review paper was published in the journal Neuron.
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