Here's How the Brain Makes Memories—and What You Can Do to Keep Your Mind Sharp
There’s a popular misconception that memory is like a file box in the brain—that we put away our recollections and then look them up when we need them. But that’s not actually how it works. Scientists suspect memories are stored in diffuse networks of neurons all over the brain; when you remember something, bits of the recollection, scattered around like puzzle pieces on the floor, are gathered up and put back together to make a complete picture.
“I think of a memory as a particular firing pattern of brain nerve cells in a network,” says Ronald C. Petersen, MD, PhD, director of the Mayo Clinic Alzheimer’s Disease Research Center. “If you’re trying to remember a meaningful childhood event, for example, you refire the pattern in the brain that happened when the event took place.”
The precise way that memories are created and then recalled, sometimes decades later, is one of the great mysteries of neuroscience. Researchers are just scratching the surface of the processes that allow us to hold on to information and experiences. What we do know, however, is that there are simple, science-backed ways to strengthen your ability to remember things (including where you left your sunglasses).
How Memories Form
Remembering begins with your senses. This Thanksgiving, for instance, your brain might take note of how good the turkey smells, how nice it feels to hug your mom, and how loud your aunt is when she’s had one too many. As your brain processes that sensory input, it creates neural connections, explains Dr. Petersen— and those connections will eventually become memories.
Your brain decides how important a memory is based on context cues, such as your level of emotion or stress at the time. The more important the recollection is, the stronger the neural connections will be, says Dr. Petersen.
“Remembering highly emotionally charged events is an important survival tool,” he points out. “Say you’re in a certain area of the woods and all of a sudden there’s a dangerous animal chasing you—you’re going to want to remember that so you won’t go to that place again.”
There are several areas of the brain that are involved in encoding and later retrieving memories, but one part—the hippocampus—is thought to play a key role in “binding together the different scattered components of memory,” says psychologist Daniel Schacter, PhD, who studies the cognitive neuroscience of memory at Harvard University. “It might function as a kind of index.”
The hippocampus is a pair of wormlike structures nestled deep inside the midbrain. It’s believed to be especially important for processing long-term memories—like your last vacation, or what your email password is.
Short-term memory is the other main type of memory, and it refers to things you need to keep in your consciousness for no more than a few seconds. “That’s the kind of memory you’re taxing if you’re trying to hold a phone number in your head before putting it into your phone,” explains Schacter. It’s also the memory you use to recall the specials the server has just recited, or measure out the correct dose printed on the label of a medication. Those bits of information appear to be stored in the prefrontal cortex, the structure that sits at the very front of your brain.
Blips and Other Issues
As impressive as human memory is, we’re all aware it’s not perfect. One common foible is the tip-of-the-tongue phenomenon, when you’re trying to remember a word but it hovers just beyond your reach (like the name of the actor who was in that movie about the thing…). Why this occurs is not well understood, but it’s normal to experience such a blockage (also known as lethologica) about once a week. It is more likely to happen when you’re tired or stressed, and also becomes more frequent with age.
Speaking of age, our brains start to shrink as early as age 30, which often results in a normal (if irritating) decline in “episodic” memory—the kind that helps us keep track of daily logistics, like whether we paid last month’s electricity bill yet, or what the heck it was we walked into a room to do.
There’s a big difference between these types of normal lapses and the memory loss and confusion caused by Alzheimer’s and other types of dementia. Normal forgetfulness is not being able to find your car keys—dementia is momentarily forgetting what they’re even for. About 5.8 million Americans have Alzheimer’s, including about 200,000 people under the age of 65. Researchers still aren’t entirely sure what causes the disease. Autopsies of people who have died from it show collections of plaques in between neurons, and tangles of errant threads of proteins within the nerve cells themselves—both of which disrupt messaging and connections.
But studies suggest that basic healthy habits—like exercise and a nutritious diet—may help protect the long-term health of your brain and boost your memory, too. Perhaps unsurprisingly, what’s good for your body is also good for your mind.
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