Аризоны их сургуулийн судлаачид нас ахих тусам тархины ой тогтоолтын системд гардаг өөрчлөлт нь доройтол бус, харин үр ашигтай байдлыг нэмэгдүүлэх зорилготой байж болзошгүй гэсэн дүгнэлтийг дэвшүүлжээ.
Хүний нас ахих тусам нарийн ширийн зүйлийг санахад оролцдог гиппокампус бүсийн үйл ажиллагаа суларч, ерөнхий мэдлэг болон төлөвлөгөөг боловсруулдаг урд талын тархины бор гадаргын үүрэг давамгайлдаг байна. Уламжлалт ойлголтоор үүнийг тархины эсүүдийн элэгдлийг нөхөх гэсэн оролдлого гэж үздэг байсан бол шинэ судалгаагаар үүнийг хувьслын явцад бүрэлдсэн дасан зохицох шинжтэй өөрчлөлт хэмээн тайлбарлажээ. Судлаачид үүнийг амьтны ертөнцөд ч ажиглагддаг нийтлэг зарчим бөгөөд нас өндөр болох тусам хуримтлуулсан мэдлэгээ бусдад түгээхэд чиглэсэн тархины оновчтой зохицуулалт байж болзошгүй гэж үзэж байна.
Perspectives on Psychological Science сэтгүүлд нийтлэгдсэн энэхүү судалгаа нь одоо байгаа судалгааны үр дүнгүүдийг дахин нягталсанд суурилсан бөгөөд шинэ нотлох баримт цуглуулаагүй болно. Уг онол нь Альцгеймерийн өвчин зэрэг насжилттай холбоотой эмгэгийг ойлгоход шинэ өнцөг нээж өгч магадгүй юм. Тухайлбал, өвчний эхэн үед гиппокампус хэт идэвхжиж байдаг нь тархины байгалийн зөв зохицуулалтыг алдагдуулж буй хэлбэр байж болох талтай.
Цаашид судлаачид хүний тархины үйл ажиллагаанд гарч буй энэхүү шилжилтийг бодит цаг хугацаанд ажиглах судалгаа хийхээр төлөвлөж байна. Энэ нь хөгшрөлтийн явцыг зөвхөн доройтол гэж харахаас илүүтэй, нас ахих тусам нийгмийн харилцаа болон хуримтлуулсан туршлагаа хуваалцахад тархи хэрхэн өөрчлөгдөж буйг илүү гүнзгий ойлгох боломж олгох юм.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
As we get older, our episodic memory – managed by the hippocampus region – gradually gets worse. That’s the memory related to specific details, like where the car’s parked or what time an appointment is.
In old age, the semantic memory, controlled by the frontal cortex, tends to become more dominant. This is the big picture, general knowledge, overall gist memory, covering the rules of hockey or capital cities.
The conventional thinking amongst neuroscientists has long been that this brain shift is our way of adapting to increasing neural wear and tear: a compensatory mechanism.
But what if it’s a deliberate choice that better suits older people, who’ve amassed much more information in their brains than younger people?
Researchers from the University of Arizona have now published a study in Perspectives on Psychological Science arguing that shifting from the hippocampus to the frontal cortex could be the brain optimizing itself rather than retreating.
“Prevailing theories of cognitive aging depict late life as a period of compensatory decline – an effort to preserve performance despite progressive neural deterioration,” write the researchers in their published paper.
“We propose instead that aging represents a continuation of development: a genetically conserved, adaptive reorganization of memory systems that parallels the brain’s earlier-life transitions.”
The researchers point to several previous studies to make their point. For example, there’s plenty of evidence of these kinds of changes happening at other periods of life: In childhood, the same shift happens, just in the opposite direction.
There’s also a case to be made that these age-related modifications aren’t reflecting an overall loss of neural plasticity, but rather a way of redeploying resources.
We know that the hippocampus is particularly demanding in terms of energy, so the brain could be saving resources for when they’re most needed.
It’s also true that some brain wiring sections actually strengthen in old age, backing up the idea that the brain isn’t faltering but intelligently readjusting.
The study points to parallels in the animal kingdom as well. As rats get older, they tend to rely more on what’s familiar too, while female African elephants become “repositories of social knowledge” in old age – so might we be doing the same?
“Taken together, findings from the animal literature suggest that memory-system reorganization in aging may not be uniquely human, but a general principle across species with extended life spans and complex social structures,” write the researchers.
There might be an evolutionary purpose to all this: For those of us lucky enough to make it to old age, the priority becomes passing on information, rather than trying to remember the specifics of day-to-day life.
The case put forward by the study might not only change the way that aging is assessed in the brain, but also provide more insight into age-related conditions like Alzheimer’s disease. For example, it might mean the true signs of disease can be more easily separated from brain changes that are actually natural and positive.
Given that Alzheimer’s is associated with an overactive hippocampus in its early stages, it’s also possible that the disease somehow derails the natural and beneficial shift in brain priorities that should happen.
It’s worth pointing out that this study doesn’t gather any new evidence, but rather reinterprets existing research to put forward 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 neural reallocation can be found. If so, it could mean a new perspective on aging in the brain, and treating age-related conditions.
“If we look at normative aging as a story of just decline, we are really missing the boat,” psychologist Fabian-Xosé Fernandez told Linda Wang at the Association for Psychological Science.
“The older brain is optimized for different things than the younger brain, predominantly the sharing of stored expertise and social relationships.”
The research has been published in Perspectives on Psychological Science.
