In the wake of last week’s presidential debate between the 78- and 81-year-old candidates—and the impression among some that President Joe Biden looked “ old and frail ,” with at least one public call for cognitive testing—much of America has had age on the brain. But what does age actually do to the brain? Fortune consulted with experts on aging to get a clearer picture. The incredible shrinking cortex “The brain undergoes many changes associated with aging, and one of them is the shrinkage of what we call the outer layer of the brain, or the cortex,” Emily Rogalski, professor of neurology at the University of Chicago and director of its Healthy Aging & Alzheimer’s Research Care Center , tells Fortune.
The cortex, she explains, is like the bark on a tree, and is the layer where brain cells live. “It’s really important to our thinking and our communication,” she says, and its shrinking tends to occur in areas related to memory, and tends to be correlated with changes in memory—which is at its peak performance, believe it or not, when we are just in our 20s or early 30s . Also vulnerable as a result are skills of attention and executive functioning.
“And all of these things are interrelated in a way, because you need to have good attention in order to remember something,” Rogalski says. “Our cognitive functions don’t just sit on little islands of, here’s memory and here’s attention, and there’s no interaction. It’s a complex system.
” A.