The memory exercise reported in the latest issue of the Journal of Neuroscience dealt with recognizing faces, but the findings apply to the more general task of trying to remember something a person sees or hears, said lead author Dale Stevens.
Stevens, a postdoctoral researcher at Harvard University, did the work while at the Rotman Research Institute at Baycrest, which is affiliated with the University of Toronto.
Older people who have to learn something should do all they can to focus on that task and eliminate potential distractions, he advised.
The study compared 10 healthy people in their 60s and 70s to a dozen younger volunteers, ages 22 to 36. Their brains were scanned while they looked at photographs of people they did not know. As each photograph was displayed for one second, the volunteers were asked if they'd seen it before in the study.
In all they saw 180 different faces, of which 120 showed up a second time. The older participants failed to recognize a face they'd already seen 43 percent of the time, compared to 26 percent for the younger volunteers.
Researchers went back to see what was going on in the brains of the volunteers when they first saw a face that they later failed to recognize. Why didn't those faces get planted in memory?
In both groups, a brain area called the hippocampus, which is involved in memory, was less active when a face failed to stick in the memory than when it did. That was no surprise. More interestingly, the older group also showed heightened activity in certain other brain areas while the younger volunteers did not.
Those areas included the auditory cortex, which plays a role in analyzing sound, and several areas involved in directing attention, Stevens said.
So what was going on? The brain-scanning machine was noisy, with lots of knocking, buzzing and banging like a jackhammer, Stevens said. Even with the earplugs the volunteers wore, "it's a little distracting," he said.