How to bring back a memory.

Details of significant experiences from decades ago may still be available if you can coax them out of your memory.

Sometimes memories of certain experiences remain crystal clear for life, like the moment you said “I do,” or the first time you held your baby in your arms. Other significant memories from long ago can be harder to recall. But they may still be with you; it just takes effort to retrieve them.

Which memories stay with us?

Of the many memories you accumulate every day, only those marked as meaningful are recorded in your brain’s long-term files. “We have a system in our brains that tags memories that are important in some way so we’ll remember them in the future,” explains Dr. Andrew Budson, a neurologist and chief of Cognitive and Behavioral Neurology at VA Boston Healthcare System.

Two things tag a memory as special:

Emotion. “Getting married is an example of a highly emotional event. In that circumstance, a whole host of brain chemicals become active as these memories are being recorded,” Dr. Budson says.

Personal significance. “You probably remember what you had for breakfast this morning and what clothes you wore yesterday. But if I were to ask you about those in a few days or a month, you’d have no memories for them because they’re just not that important to you,” Dr. Budson explains.

Aging affects retrieval

Sometimes even special or important memories are harder to remember. Several age-related factors contribute to this loss of recall:

Memory goes downhill after age 30.

“There’s good evidence that our ability to retrieve information peaks between ages 20 and 30. By the time we’re in our 50s, the frontal lobes, which are in charge of searching for memories, don’t work as well as they used to,” Dr. Budson says.

Memories fade with time. If you haven’t thought about a memory in years, it won’t be as vivid or strong as it used to be.

“By not revisiting the memory, you’re telling your brain it’s not important, and other memories might be laid on top of it,” Dr. Budson says.

We need help to jog our memory. “When we’re younger, an internal cue — just thinking of something — can help retrieve a memory,” Dr. Budson says. “But when we’re older, we rely more on external cues to retrieve memories, like a sound or an image.”

Cue the memory

To reactivate an old memory, you must think about the senses that were engaged as the memory was being recorded. That’s because as you experienced something special or important, your perceptions — images, sounds, smells, tastes, touches, thoughts, or feelings — were being stored in one part of the brain (the cortex) and then bound together as a memory by another part of the brain (the hippocampus) and tagged so the frontal lobes could retrieve the pattern of information later.

A cue from your environment (such as hearing a song) or a cue that you generate (such as thinking about your high school graduation) can help you retrieve a memory. “The more specific the cues are for the episodes of life you’re trying to remember, the more likely it is you’ll have a pattern match and pull up an old memory,” Dr. Budson says.

Ideas for cues

Because you may not spontaneously recall cues related to a long-forgotten memory, you’ll have to generate some. Dr. Budson recommends that you try these strategies:

• Look at old photographs of your home, family, or friends.
• Read a poem you wrote or liked to read when you were younger.
• Hold an old article of clothing you saved.
• Read an old letter, personal journal, or newspaper article.
• Listen to an old song that you or someone in your family loved.
• Cook a meal your mom or dad used to make for you.
• Smell something that may jog your memory, like a book, pillow, perfume, or food.
• Visit a place from your younger days.
• Watch an old movie or TV show.

Additional suggestions

Be still as you try to summon old memories; close your eyes at times and focus on the sights, sounds, smells, thoughts, and feelings associated with each one.

And when you do recall memories, write them down (before you forget them) and reinforce them by visiting them often in your mind if they’re pleasing or helpful.

“You really can travel back in time to a particular experience in your life,” Dr. Budson says. “And cuing one memory will often lead to another.”