Remember that great summer vacation you took last year? When you think back on it, you might see flashes of a day you spent swimming or a night spent watching fireworks explode high in the sky.

But how do you store those images, so you can enjoy them later? It's your memory — and it's part of your complex and multitalented brain.

What Is Memory?

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

You probably know your brain has different parts. Some of them are important for memory. The hippocampus (say: 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?

As wonderful as memory is, it isn't always perfect. It's normal to occasionally forget the name of somebody you just met or where you put your shoes. And of course, everyone has forgotten an answer on a test. Darn! You knew that one, too!

It's also typical for people to forget more things as they grow older. Your parents or grandparents 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's disease. In this disease, deposits build up and nerve cells stop working leading to memory loss.

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

Brain Injuries Affect Memory

At any age, an injury to the head and brain can cause trouble with somebody's 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 your head by wearing your seatbelt in the car and wearing a helmet when you skate, play football, ride your bike, skateboard, or wear roller sneakers.

You may have heard about a memory problem called amnesia (say: 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 you see on TV or in the movies. People rarely forget their own names and they usually get better slowly, instead of all at once because something dramatic happens — like getting kissed by a dreamy prince or princess!

The most common cause of amnesia is a traumatic brain injury(TBI). A TBI is caused by a severe hit to the head. Traumatic brain injuries 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 National Football League 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 of a Memory Problem

A person might — or might not — be able to notice signs of his or her own memory problem. If someone has suffered a brain injury, doctors, nurses, 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 in Alzheimer's 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.

What Will the Doctor Do?

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 patient'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 his or her memory will improve.

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

Most memory problems affect older people, so what can you do for your memory if you're 8, not 88? In addition to remembering to wear your helmet, use your brain! By doing challenging activities, like reading and doing puzzles, you can exercise your mind so you'll be remembering great memories for many years to come!