Memory: How the Brain Remembers & Forgets

How the Brain Stores Memories

When an event happens, when you learn something, or when you meet someone, the brain determines whether that information needs to be saved. If the brain judges the information important, it places it in memory "files."

The brain has different parts, and some are important for memory. The hippocampus (hih-puh-KAM-pus) is one of the more important parts of the brain that processes memories.

Old information and new information, or memories, are thought to be processed and stored away in different areas of the cerebral cortex, or the "gray matter" of the brain — the largest, outermost part of the brain.

What Can Go Wrong With Memory?

Memory isn't always perfect. It's normal to occasionally forget the name of somebody you just met or where you put your shoes. And everyone has forgotten an answer on a test.

It's also typical for people to forget more things as they grow older. Some older adults might joke about having a "senior moment." That's when they forget something.

But some memory problems are serious, such as when a person has Alzheimer disease. That’s when deposits build up and nerve cells stop working, leading to memory loss.

Strokes, which also affect older people, are another medical problem that can impact someone's memory. A stroke is when blood doesn't get to all the parts of the brain, either because there’s a blockage in the pathway or because a blood vessel (which carries the blood) bursts.

Brain Injuries Can Affect Memory

At any age, an injury to the head and brain can cause trouble with memory. Some people who recover from brain injuries need to learn old things all over again, like how to talk or tie their shoes. That's why it's so important to protect the head by wearing a seatbelt in the car and wearing a helmet for activities where there’s a risk of head injury. For example, when playing football, biking, skateboarding, inline skating, roller skating, or figure skating.

Amnesia

One memory problem is called amnesia (am-NEE-zhuh). This is when someone can't remember things that happened recently and sometimes even things that happened long ago. It's not usually like it is in shows and movies. People rarely forget their own names, and they usually get better slowly instead of all at once because something dramatic happens.

Traumatic Brain Injury

The most common cause of amnesia is a traumatic brain injury (TBI). A TBI is caused by a severe hit to the head. TBIs can happen in a lot of ways and can be severe enough to cause a coma (prolonged unconsciousness), or a person may just be stunned without even being knocked out (like in some concussions).

Car accidents, bike accidents, and falls can cause TBIs. If you've ever seen someone take a hit to the head in a football game, you may have seen the player being questioned on the sidelines. The doctor may ask the person some basic questions — like what happened, where they are, and what team they're playing. Not knowing the correct answers could be the first sign of a brain injury.

Abusing alcohol or using illegal drugs is another way to injure the brain and cause memory problems. Hallucinogens (like LSD or PCP) can alter certain chemicals in the brain that actually make memories harder to recall.

Signs & Symptoms of Memory Problems

A person might — or might not — be able to notice signs of a memory problem. If someone has had a brain injury, healthcare professionals and family members will be on the alert for signs of trouble.

Someone who has a memory problem will be unable to remember important things for varying lengths of time. The more severe the illness or injury, the longer the memory loss is likely to last. Some people forget just the moments right before and after an injury, which is not unusual with a concussion. Sometimes, these memories come back.

More significant problems with memory, such as with Alzheimer disease, might make it hard to remember what happened days, weeks, months, or even years ago, and it can be difficult to learn and remember new things.

Diagnosing & Treating Memory Problems

Any time a person has been hit in the head, it's important to see a doctor. A doctor will test the person's ability to recall events, names, or places by asking lots of questions. In the case of a suspected brain injury, a doctor may also want to take a picture of the person’s brain and skull using something called a CT scan.

If the person has memory loss from a head injury, the doctor will design a treatment plan to help the brain heal and, if necessary, to help the person relearn things that have been forgotten. If the memory problem is due to drug or alcohol use, the person needs to stop abusing these substances before memory will improve.

With strokes, memory can return but it depends on severity and location of the stroke in the brain. With Alzheimer, lost memory can’t be restored, but scientists are working on medicines they hope someday will prevent this kind of memory loss.

Keeping Memory Healthy

Most memory problems affect older people, but there are things you can do to help protect your memory. In addition to keeping the head safe from injury, challenging activities, like reading and doing puzzles, can exercise the mind and help keep memories alive for years to come.