Aging memories may not be 'worse', just 'different'

Date:
August 11, 2020
Source:
Washington University in St. Louis
Summary:
A study adds nuance to the idea that an aging memory is a poor one
and finds a potential correlation between the way people process
the boundaries of events and episodic memory.



FULL STORY ========================================================================== "Memory is the first thing to go."

========================================================================== Everyone has heard it, and decades of research studies seem to confirm
it: While it may not always be the first sign of aging, some faculties, including memory, do get worse as people age.

It may not be that straightforward.

Zachariah Reagh, assistant professor of psychological and brain sciences
in Arts & Sciences at Washington University in St. Louis, looked at the
brain activity of older people not by requiring them to recite a group
of words or remember a string of numbers. Instead, Reagh looked at a "naturalistic approach," one that more closely resembled real-world
activities.

He found that brain activity in older adults isn't necessarily quieter
when it comes to memory.

"It's just different," he said.



==========================================================================
The study results were published today in the journal Nature
Communications.

Common tests of memory involve a person's ability to remember a string
of words, count backward, or recognize repeated images. "How many times
do you suspect a 75-year-old is going to have to remember, 'tree, apple, cherry, truck?'" asked Reagh, first author on the paper with Angelique Delarazan, Alexander Garber and Charan Ranganath, all of University of California, Davis.

Instead, he used a data set from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) that included functional MRI (fMRI) scans of people watching an 8-minute movie. "There were no specific instructions, or a
'gotcha' moment," Reagh said. "They just got to kick back, relax and
enjoy the film." But while they may have been relaxing, the subjects'
brains were hard at work recognizing, interpreting and categorizing
events in the movies. One particular way people categorize events is by
marking boundaries -- where one event ends and another begins.

An "event" can be pretty much anything, Reagh said. "This conversation,
or a component of it, for example. We take these meaningful pieces
and extract them out of a continuous stream." And what constitutes a
boundary is actually consistent among people.



==========================================================================
"If you and I watch the same movie, and we are given the instruction to
press a button when we feel one meaningful unit has ended, you and I will
be much more similar in our responses than we are different," Reagh said.

When looking at the fMRI results -- which use changes in blood flow
and blood oxygen to highlight brian activity -- older adults showed
similarly increased activity as a control group at the boundaries of
events. That's not to say that brains of all ages are processing the information similarly.

"It's just different," Reagh said. "In some areas, activity goes down
and, in some, it actually goes up." Overall activity did decline pretty reliably across ages 18-88, Reagh said, and when grouped into "younger,
middle aged, and older," there was a statistically reliable drop in
activity from one group to another.

"But we did find a few regions where activity was ramped up across age
ranges," he said. "That was unexpected." Much of the activity he was interested in is in an area of the brain referred to as the posterior
medial network -- which includes regions in the midline and toward the
backside of the brain. In addition to memory, these areas are heavily
involved in representing context and situational awareness. Some of
those areas showed decreased activity in the older adults.

"We do think the differences are memory-related," Reagh said. At the boundaries, they saw differences in the levels of activity in the
hippocampus that was related to memory in a different measurement --
"story memory," he called it.

"There might be a broad sense in which the hippocampus's response to
event boundaries predicts how well you are able to parse and remember
stories and complex narratives," no matter one's age, Reagh said.

But for older adults, closer to the front of the brain, particularly
the medial prefrontal cortex, things were looking up.

Activity in that area of the brain was ramped up in older adults. This
area is implicated in broad, schematic knowledge -- what it's like to
go to a grocery store as opposed to a particular grocery store.

"What might be happening is as older adults lose some responsiveness
in posterior parts of the brain, they may be shifting away from the
more detailed contextual information," Reagh said. But as activity
levels heighten in the anterior portions, "things might become more
schematic. More 'gist-like.'" In practice, this might mean that a
20-year-old noting an event boundary in a movie might be more focused on
the specifics -- what specific room are the characters in? What is the
exact content of the conversation? An older viewer might be paying more attention to the broader picture -- What kind of room are the characters
in? Have the characters transitioned from a formal dinner setting to
a more relaxed, after-dinner location? Did a loud, tense conversation
resolve into a friendly one? "Older adults might be representing events
in different ways, and transitions might be picked up differently than,
say, a 20-year-old," Reagh said.

"An interesting conclusion one could draw is maybe healthy older adults
aren't 'missing the picture.' It's not that the info isn't getting in,
it's just it's getting in differently."

========================================================================== Story Source: Materials provided by
Washington_University_in_St._Louis. Original written by Brandie
Jefferson. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zachariah M. Reagh, Angelique I. Delarazan, Alexander Garber, Charan
Ranganath. Aging alters neural activity at event boundaries in the
hippocampus and Posterior Medial network. Nature Communications,
2020; 11 (1) DOI: 10.1038/s41467-020-17713-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200811153916.htm

--- up 3 weeks, 6 days, 1 hour, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)