As we age, our episodic memory – managed by the hippocampus region – gradually deteriorates. This is memory tied to specific details, like where the car is parked or the time of an appointment.
In old age, semantic memory, controlled by the frontal cortex, tends to become more dominant. This is an overview, general knowledge, general memory, covering the rules of hockey or capitals.
Conventional thinking among neuroscientists has long been that this brain change is our way of adapting to increasing neuronal wear and tear: a compensatory mechanism.
But what if this is a deliberate choice that is better suited to older people, who have accumulated much more information in their brains than younger people?
Researchers from the University of Arizona published a study in Perspectives on psychological science arguing that the shift from the hippocampus to the frontal cortex could be the brain optimizing rather than moving backwards.
“Prevailing theories of cognitive aging describe late life as a period of compensatory decline – an effort to preserve performance despite progressive neuronal deterioration,” the researchers write in their published paper.
“Rather, we propose that aging represents a continuation of development: a genetically conserved and adaptive reorganization of memory systems that parallels earlier brain transitions.”
The researchers cite several previous studies to make their point. For example, there is ample evidence of this type of changes occurring in other periods of life: in childhood, the same change occurs, but in the opposite direction.
There is also a case to be made that these age-related changes do not reflect an overall loss of neuronal plasticity, but rather a way of redeploying resources.
We know that the hippocampus is particularly demanding in terms of energy, so the brain could save resources for times when they are needed most.
It is also true that certain sections of the brain’s wiring strengthen with old age, supporting the idea that the brain does not weaken but intelligently readjusts.
The study also highlights parallels in the animal kingdom. As rats age, they also tend to rely more on what is familiar to them, while female African elephants become “repositories of social knowledge” with old age – so could we do the same?
))>“Taken together, findings from the animal literature suggest that reorganization of the memory system during aging may not be uniquely human, but is a general principle across species with extended lifespans and complex social structures,” the researchers write.
There might be an evolutionary purpose to all of this: for those of us fortunate enough to reach old age, the priority becomes transmitting information, rather than trying to remember the specifics of daily life.
The arguments put forward by the study could not only change the way aging is assessed in the brain, but also provide more insight into age-related diseases like Alzheimer’s. For example, it could mean that true signs of an illness can be more easily distinguished from brain changes that are actually natural and positive.
Since Alzheimer’s disease is associated with an overactive hippocampus in its early stages, it is also possible that the disease somehow derails the natural, beneficial shift in brain priorities that should be occurring.
It should be emphasized that this study does not gather any new evidence, but rather reinterprets existing research to present a strong argument.
The next step for what the researchers call their adaptive aging hypothesis will be to follow real-world subjects over time to analyze changes in the brain to see if signs of this neuronal reallocation can be found. If so, it could mean a new perspective on brain aging and the treatment of age-related conditions.
“If we think of normative aging as just a story of decline, we’re really missing the boat,” psychologist Fabian-Xosé Fernandez told Linda Wang of the Association for Psychological Science.
“The older brain is optimized for different things than the younger brain, primarily for sharing stored expertise and social relationships.”
The research was published in Perspectives on psychological science.
Gn Health
