The science behind senior moments

By Melissa Pandika, the Daily Dose, Oct 2, 2017

Because for the elderly, drawing a blank might stem not from a lack of information but an information overload.

Let’s say you’ve met an attractive stranger at a wedding. As he starts talking about his job as a patent attorney, you overhear another guest chatting about her trip to Bermuda and someone else consoling a recent divorcé. The next morning, you gush about the cute guest to your girlfriends. “So, what does he do for a living?” they ask.

If you’re younger than 60, you’ll probably answer “patent law” immediately; over 60, and you’ll struggle to muster a response. While plenty of studies would blame our memory’s tendency to dwindle with age, leaving behind a yawning abyss, a recent study led by Georgia Institute of Technology researchers offers a less dismal explanation. Rather than drawing a complete blank, older adults’ brains store not only important information but also irrelevant details. The findings suggest they spend more time stitching together an entire memory — including snippets of background conversation, for instance — which makes them more hesitant as they try to recall important information. Which is to say:

SENIOR MOMENTS STEM FROM INFORMATION LOAD — NOT LACK OF INFORMATION.
Past studies have shown that older adults have a harder time filtering irrelevant clutter and focusing on the situation at hand, but we still don’t really know how that distraction affects their memory. To find out, the study authors recruited a group of college-age students and adults over 60, and hooked them up to an EEG machine, which measured their brain activity. First, a screen displayed a series of images of everyday objects (like a chair or stop sign), each flanked by a color and a scene. The participants then responded to a question about whether the object was likely to be found in the displayed color, or as part of the displayed scene. They received instructions to focus only on the context cue — the color or the scene — specified in the question.

An hour later, the screen displayed another series of objects, again flanked by a color and a scene. The participants specified whether or not they had seen the object in the earlier trial. If they did, the screen asked whether it was accompanied by the same color or scene as before. Participants responded on a scale of 1 to 4, ranging from “certain match” to “certain mismatch,” to measure their confidence in their memories. Throughout the study, the researchers recorded the participants’ response times.

Both young and old participants accurately recalled far more object-color or object-scene associations for the objects they were told to pay attention to — aka attended objects — than for those they were told to ignore (unattended objects). But they differed in how confidently they responded. Younger adults had high confidence in associations for both attended and unattended objects. In contrast, older adults had low confidence recalling the associations for both classes of objects. They also spent more time piecing together information as they tried to recall the associations, suggesting “an additional search process” as they traveled back in time to reconstruct the memory, says Taylor James of Georgia Tech, the study’s lead author. Older adults also had higher brain activity as they tried to retrieve these memories. “We think of older adults as remembering less, but in fact older adults might remember more in situations where they’re distracted,” says Audrey Duarte, an associate professor of psychology at Georgia Tech, “but not necessarily the critical information.” That might be partly because the prefrontal cortex — the brain region important for attention and decision-making — shrinks with age. So do the numbers of neurons that release a class of neurotransmitters that includes dopamine, also crucial in attention.

To be sure, the new study only approximates what happens in the real world. Asking whether an object is likely to be a certain color relies on a “brain area concerned with processing who or what in an event as opposed to the context — where, when or how,” says Charan Ranganath, a professor of psychology at the University of California, Davis. “They could have maybe asked about a situation you could see this in … like would you find this in an auction?” And although the study presented only visual cues, real-world events include a richer array of sensory information. Duarte says her team might include auditory cues in follow-up work.

Still, “that doesn’t detract from their big point,” Ranganath says. Amid popular portrayals of “senior moments” as omens for an inevitable spiral toward cognitive decline, the new study offers a more nuanced portrait of aging. “We need to start thinking about aging not just as this process that your brain is deteriorating, but that aging comes with some costs and benefits.”