The brain is truly a marvel. A seemingly endless library, whose shelves house our most precious memories as well as our lifetime’s knowledge. But is there a point where it reaches capacity? In other words, can the brain be “full”?
The Experiment
The paper’s authors set out to investigate what happens in the brain when we try to remember information that’s very similar to what we already know. This is important because similar information is more likely to interfere with existing knowledge, and it’s the stuff that crowds without being useful.To do this, they examined how brain activity changes when we try to remember a “target” memory, that is, when we try to recall something very specific, at the same time as trying to remember something similar (a “competing” memory). Participants were taught to associate a single word (say, the word sand) with two different images – such as one of Marilyn Monroe and the other of a hat.
They found that as the target memory was recalled more often, brain activity for it increased. Meanwhile, brain activity for the competing memory simultaneously weakened. This change was most prominent in regions near the front of the brain, such as the prefrontal cortex, rather than key memory structures in the middle of the brain, such as the hippocampus, which is traditionally associated with memory loss.
Better to Forget
In daily life, forgetting actually has clear advantages. Imagine, for instance, that you lost your bank card. The new card you receive will come with a new personal identification number (PIN). Research in this field suggests that each time you remember the new PIN, you gradually forget the old one. This process improves access to relevant information, without old memories interfering.When we acquire new information, the brain automatically tries to incorporate it within existing information by forming associations. And when we retrieve information, both the desired and associated but irrelevant information is recalled.
The Curse of Memory
A very small number of people are able to remember almost every detail of their life in great detail; they have hyperthymestic syndrome. If provided with a date, they are able to tell you where and what they were doing on that particular day. While it may sound like a boon to many, people with this rare condition often find their unusual ability burdensome.Some report an inability to think about the present or the future, because of the feeling of constantly living in the past, caught in their memories. And this is what we all might experience if our brains didn’t have a mechanism for superseding information that’s no longer relevant and did indeed fill up.
It’s believed this represents a failure to “consolidate” or transfer new memories into long-term memory. But the processes and impact of this form of forgetting are still largely unexplored.
What studies in this area are demonstrating is that remembering and forgetting are two sides of the same coin. In a sense, forgetting is our brain’s way of sorting memories, so the most relevant memories are ready for retrieval. Normal forgetting may even be a safety mechanism to ensure our brain doesn’t become too full.