Researchers at The University of Texas at Dallas Center for Vital Longevity (CVL) found that age-related memory decline involves complex brain changes. Michael Rugg, PhD, CVL director, led a study published in The Journal of Neuroscience, revealing multiple mechanisms driving this decline in functional specialization of brain regions over time.

As people age, even in good health, their brains become less precise in how they process different types of visual information, leading to a decline in memory performance. Researchers used functional MRI (fMRI) to study brain activity patterns as participants viewed images of panoramic scenes and objects. By repeating some images, they measured the brain’s response to both image categories and individual stimuli. The study included groups of healthy young adults (average age 22) and older adults (average age 69), totaling 48 participants.

“At the category level, as we expected, we found that the older group showed reduced selectivity for scenes compared to the younger group, but not for objects,” Rugg says. “But when we looked at individual items, selectivity for both scenes and objects were reduced in the older group. This implies that the mechanisms driving dedifferentiation at the single item level are not the same as those at the category level. We had, to this point, assumed they were one and the same mechanism.”

The implication, Rugg says, is that knowing how selective an individual’s brain is for categories does not predict how selective the brain will be for individual items.

“There isn’t a one-size-fits-all theory of age-related neural dedifferentiation,” says Rugg. “This has important implications for how we understand and investigate age differences in neural selectivity, some measures of which are predictive of memory performance. Moving forward, we’re going to have to be more cautious in how we generalize from category-level findings to what’s happening more broadly in the brain as people grow older.”

Corresponding author Sabina Srokova, PhD, says the findings suggest at least two independent factors drive the reduction in selectivity in older adults.

“We know that the neural mechanisms underlying category-level selectivity are robustly related to memory success across the adult lifespan,” Srokova says. “However, the factors that contribute to the relationship between neural selectivity, age and memory abilities remain unknown.”Now that we believe different neural mechanisms are at work in these two contexts, it’s crucial that we continue to study them separately.”

Researchers will next examine the mechanisms that contribute to age-related declines in category-level selectivity using simultaneous recording of eye movements during fMRI scanning.