Until about ten years ago, most researchers thought that forgetting was a passive process in which memories, unused, decay over time like a photograph left in the sunlight. But then a handful of researchers who were investigating memory began to bump up against findings that seemed to contradict that decades-old assumption. They began to put forward the radical idea that the brain is built to forget.
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Because the hippocampus is involved in memory formation, [neuroscientist Paul] Frankland and his team wondered whether increasing neurogenesis in adult mice could help the rodents to remember.
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Rather than making the animals’ memories better, increasing neurogenesis caused the mice to forget more. As contradictory as that initially seemed to Frankland, given the assumption that new neurons would mean more capacity for (and potentially better) memory, he says it now makes sense. “When neurons integrate into the adult hippocampus, they integrate into an existing, established circuitry. If you have information stored in that circuit and start rewiring it, then it’s going to make that information harder to access,” he explains.
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The environment is changing constantly and, to survive, animals must adapt to new situations. Allowing fresh information to overwrite the old helps them to achieve that.
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