Faulty memory fails to ‘chunk’ events

WASHINGTON U. – ST. LOUIS (US) — How older adults perceive life events can hurt their ability to remember, but breaking the day into meaningful events can help them recall better.

Grandpa’s stories often begin with the phrase, “Have I ever told you about the time…?” What he doesn’t know is that, yes, he has told you about that time, and he has told you many times before.

Why is this situation so typical of our conversations with older adults? A recent study suggests it may be due to the changing way we perceive events in our lives as we age. The study finds that this perception is influenced by a part of the brain called the medial temporal lobes (MTL), which decline in functioning in old age.

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“The traditional view of MTL is that it helps us with episodic memory,” says Heather Bailey, a postdoctoral fellow in the Dynamic Cognition Laboratory at Washington University in St. Louis.

Episodic memory is a type of long-term memory, specifically our memory for events such as our 21st birthday, what we ate for breakfast, or our last conversation with a grandparent. However, a more recent view of MTL—one supported by the current study—suggests it is not just responsible for helping us remember the past.

Chunks and segments

“More recent research suggests that MTL is important for helping us identify patterns in our experiences, and chunk and segment them into meaningful events while we’re experiencing them,” Bailey says.

“Chunk” and “segment” are lingo used in segmentation theory to describe the way in which our brains mentally chop up our days. For example, when thinking back on what you did yesterday, you might remember waking up, showering, getting dressed, drinking coffee, driving to work, and so on. Each of these activities is a “chunk” that your brain created and stored in memory.

“It’s not like you press a record button and your brain records your day and then, when you want to think back on it, you’re just hitting a play button and watching a continuous stream of 24 hours. Your brain is naturally chunking the events in your day into discrete parts,” Bailey says.

In their study, published by the journal Psychological Science, Bailey, Jeffrey Zacks, professor of psychology, and their colleagues investigated the connection between how people perceive and chunk everyday events and later remember those events.

‘Viewing and chunking’

In their study, older adults were shown short movies of people doing everyday tasks, such as a woman making breakfast or a man building a Lego ship. While watching the movie, they were instructed to press a button whenever they thought one part of the activity was ending and a new part was beginning (i.e., separate the movie into “chunks”). After the movie ended, they were asked to recall what happened.

In addition to assessing memory for the movies, the size of the older adults’ MTL was measured using structural MRI. The purpose of the study was to examine the effects of a degraded (i.e., smaller) MTL on how well people chunk and remember everyday events. The study included both healthy older adults and older adults with Alzheimer’s disease, some of who had degradation of their MTL.

“Older adults in the study who showed atrophy in MTL showed decline in memory for these everyday activities, and also showed decline in segmenting and chunking these events as they were happening,” Bailey says. “MTL accounted for a huge portion of this relationship we saw between segmentation and memory.”

This means that what people are doing while they’re watching movies or going through their daily lives—how well they’re chunking their experiences into separate memories—has a strong influence on how well they will remember those experiences in the future. How well they are able to chunk and remember is partly due to how well their MTL is functioning, the study finds.

Train the memory

“Alzheimer’s disease attacks MTL in the early stages of the disease,” says Bailey. “But even with MTL atrophy, you may be able to train people to chunk better, which might help them remember their everyday activities better, too.”

Forgetfulness is characteristic of the aging mind and conversations with our aging relatives. This study suggests that the problem may not just be with the process of recalling memories for events, but also with the process of viewing and chunking the events as they unfold.

So, memory improvement for older adults would come from working harder to form new memories better, rather than working harder to bring to mind older memories that already have formed. In this way, how we perceive the world is a strong predictor of how we’ll remember it in the future.

As part of their future research, Bailey and colleagues will design studies to actually combat memory impairment in older adults.

“We want to investigate further this link between event perception and memory. We want to see if we can intervene at an early point in perception, if it will affect memory,” Bailey says.

Source: Washington University in St. Louis