While most children can easily imagine themselves as astronauts, athletes or superheroes, make-believe might not be so easy for the kids' grandparents.

Researchers have long known that recalling memories of personal events is harder for older adults than younger ones.

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Recent brain imaging studies have shown that people use the same mechanisms in the brain to imagine as they do to remember, suggesting that older adults may have as much trouble imagining as they do remembering.

A new study, detailed in the January issue of the journal Psychological Science, investigated just that and found that younger adults were better at telling details of past, remembered events and future, made-up ones than older adults.

Episodic memory

The kind of memories we recall when we remember past personal events are called episodic memories. These are generally more vivid than other types of memory and contain more pieces of information that can be replayed or relived in the mind.

While other kinds of memory, such as semantic memory, are more about remembering facts, episodic memories are made up of the different pieces of information you remember from the event: what you saw, what you heard, how you felt.

"So when you go to re-experience or remember these events, you actually ... your brain actually has to locate and identify and reactivate all those of bits of information and kind of bring them together into kind of a coherent event that you remember," said study leader Donna Rose Addis of Harvard University.

The hippocampus is the part of the brain responsible for hunting down all those pieces and putting them back together to form the memory. The hippocampus is known to show decline in function as a person ages, possibly accounting for the loss of episodic memory.

Neuroimaging studies suggest that when people imagined themselves in the future, they used similar brain mechanisms as when recalling a memory.

Studies of severe amnesiacs who had trouble imagining also suggested a link between the two processes.

"Our theory of how one puts together a future event is that you know, you take bits of information from past events and you kind of recombine those and integrate them into some new scenario that hasn't happened before," Addis explained.

Old vs. young

Because older adults have a harder time putting together the bits and pieces of memories, Addis and her colleagues predicted that seniors would find imagining harder than young adults, "not only because they probably can't find the details in the first place, but then also to recombine them and integrate them ... into a meaningful kind of scenario might be difficult," she told LiveScience.

In Addis's study, participants were given a cue word (always a noun — for example, "shoe"), and were then instructed to either remember a past event or imagine a future one, within a certain time frame.

When the young adults recalled a past event, they were able to provide rich details about the scene and how they felt, Addis said, "almost like they're back there."

Older adults tended to tell more facts, with less visual or emotional details.

The same happened when both groups were asked to imagine a future event — young adults tended to provide more details from episodic memory, while older adults told more facts.

Addis stressed that the findings aren't saying that all older adults have no imagination, but that "it's those people that have trouble remembering in detail that also have trouble imagining in detail."

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