What if all those annoying byproducts of an aging brain — the misplaced car keys, the elusive name of that neighbor down the block — were not looming indications of dementia but simply a normal sign of healthy cognitive adaptation?
It’s not just wishful thinking on my part; there’s actually a fair amount of research to buttress such a claim. And it may help seniors understand how to use their brains more effectively while tamping down the occasional bout of Alzheimer’s angst.
As Fabian-Xosé Fernandez, PhD, explains it, what is happening in the brain as we grow older is a shift in neural prioritizing: Wisdom becomes more important than details. “If we look at normative aging as a story of just decline, we are really missing the boat,” he says. “The older brain is optimized for different things than the younger brain, predominantly the sharing of stored expertise and social relationships.”
Fernandez, an associate professor of cognition and neural systems at the University of Arizona, and his team this month published a paper challenging the conventional view of cognitive decline, arguing that the gradual failure of episodic memory is a natural — and positive — phase of human development. This “adaptive-aging hypothesis,” in which the brain gradually focuses more on the broader meaning of things than on specific details, explains why seniors make better teachers, mentors, and storytellers than their younger peers, they note.
Their report, published in Perspectives on Psychological Science, cites research based on molecular biology and neuroimaging to show how the brain gradually shifts the way it uses information as we grow older. In our younger years, the brain depends on the hippocampus, which captures and stores experiential details, more than on the frontal cortex, which is designed to absorb what Fernandez calls the “gist” of things. In our later years, that relationship naturally shifts, as the brain relies more on the frontal cortex.
“When you’re younger, the hippocampus turns on because you don’t have a knowledge base or know how the world works,” he says. “A kid absorbs information like a sponge because they are building an archive of information. In early life, the balance is tilted toward recollecting declarative memories with precision, detail, and context.”
As we grow older and understand the larger forces that shape our lives, he adds, the details we confront become less important to our ability to navigate than integrating the overall experience with the knowledge we have already accumulated.
It’s a developmental feature that has been observed in both human and animal models, Fernandez notes, which suggests there’s an evolutionary purpose involved. From that perspective, the neurological shift isn’t necessarily a response to a decline in episodic memory, but a natural process of adaptation designed to ensure valuable information is communicated to the next generation.
“Given those goals, it makes sense that you aren’t interested in nitty-gritty details,” he explains. “You are interested in safeguarding the vast knowledge you already have. Evolution may be saying that if you make it long enough, there’s a need to transmit this information, so we put into motion biological changes that enforce and protect your semantic and autobiographical memories.”
That’s not to say we’ve been mistaking true cognitive decline for some healthy evolutionary neuroadaptation. Though researchers continue to search for some consensus on the cause of Alzheimer’s, Fernandez suggests that it may involve some disruption in the brain’s salutary shift in focus from the hippocampus to the frontal cortex.
“In normative aging, hippocampal activation is deemphasized, which is probably what should be happening in a 70-year-old. But in many cases of Alzheimer’s, it turns out the hippocampus is hyperactive,” he explains. “This beautiful developmental transition is completely disrupted in Alzheimer’s disease by pathological processes that mess with episodic memory and interfere with circuits that allow you to think about your own life, lexicon, and vocabulary.”
And focusing on rehabilitating a senior’s episodic memory may be less constructive than encouraging them to engage socially and spread their wisdom. “There is tremendous value there, and we don’t do a good job of unlocking it,” he says.
There’s some consolation to hear Fernandez say that people my age shouldn’t be so “hippocampal-centric.” And if I believed there was some demand for the meager wisdom I may have accumulated, I’d happily unlock it. That is, if I could remember where I left the key.
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