A New Type Of Phantom Memory Has Been Found In The Human Brain

一種新型的記憶在人腦中被發現

A NEW TYPE OF MEMORY – KNOWN AS PRIORITIZED LONG-TERM MEMORY – HAS BEEN DISCOVERED. AGSANDREW/SHUTTERSTOCK

一種新型的記憶:一種優先的長期記憶已經被發現。(圖片來源:AGSANDREW/SHUTTERSTOCK

 

A major spanner has been thrown into the works of the leading theory on memory, after researchers discovered that the brain is capable of silently” storing information, creating ghost-like memories that have no neural signature.

It is widely accepted that two types of memory exist. The first of these is known as working memory, and becomes activated when we process new information, keeping it in our minds and focusing on it to ensure we don’t forget it. This is largely controlled by the hippocampus, where neurons spring into action and fire continuously as we maintain our concentration on whatever it is we are trying to remember.

 

主流記憶理論迎來重大的革新,研究人員發現大腦能默默地存資訊,製造出幽靈一般的記憶,這種記憶沒有經過神經的活動。有兩種記憶的存在被廣泛接受。第一種是工作記憶(working memory),當我們接收新資訊時會活化,資訊會被我們記住,而且我們會專注在它上面以確保我們不會忘記。這樣的記憶主要被海馬迴( hippocampus)控制,在海馬迴中,當我們專注在記憶東西時,神經會持續活化。

 

Long-term memories, meanwhile, are stored in the brain’s cortical regions, and are encrypted into specific neural pathways called engrams that become active only when we retrieve these specific memories.

However, in a new study in the journal Science, researchers report the discovery of a third type of memory, which they are calling prioritized long-term memory.” The main difference between this and other types of memory is that it doesn’t appear to be actually stored anywhere in the brain, yet can somehow still be recalled when needed.

The team used functional magnetic resonance imaging (fMRI) to monitor the brain activity of participants as they viewed a series of words, faces, and shapes. Thanks to a machine learning algorithm, the researchers were able to identify the particular activity patterns associated with each of these stimuli.

 

長期記憶同時也儲存在大腦的皮層區域,並且經由稱為「記憶痕跡」的特定的神經路徑加密,它只會在我們回想特定記憶時活化。然而,一分刊載在科學期刊(Science)的研究指出,研究人員發現了第三種類型的記憶,他們稱這種記憶為「優先長期記憶」。這種記憶和其他記憶類型的主要差別在於,這種記憶不是真的被儲存在大腦中,但是卻依然可以被回想。這個研究團隊使用功能性磁共振成像(functional magnetic resonance imaging fMRI)來觀察實驗參與者在看到一系列文字、臉、形狀時的大腦活動。感謝機器學習演算法,工作人員得以辨別每一種刺激所對應的大腦特定活動模式。

They then showed subjects pairs of items, which caused two different activity patterns to emerge in their brains simultaneously. When participants were told to focus on just one of these items and ignore the other, one of these patterns disappeared, suggesting that it had been erased from their working memory.

 

接著這個團隊秀了一些成對的物體給參與者看,這個刺激在他們的腦內同時引起了兩種不同的大腦活動模式。再來實驗參與者被要求只專注在其中一個物體上,忽略另一個,其中一個大腦活動模式就消失了,這個現象表示它從

參與者的工作記憶中被刪除了。

Scientists had believed that working memory requires neurons to be continuously firing. Andrii Vodolazhskyi/Shutterstock

科學家相信工作記憶需要神經持續的活化。(圖片來源: Andrii Vodolazhskyi/Shutterstock

 

Yet in spite of this, subjects were still able to recall this forgotten item when later asked what they had seen, indicating that it still existed somewhere in their memory even though no neurons appeared to be actively remembering it.

People have always thought neurons would have to keep firing to hold something in memory,” explained study co-author Bradley Postle in a statement. But we’re watching people remember things almost perfectly without showing any of the activity that would come with a neuron firing.”

The study authors also found that by magnetically stimulating the brain regions that were associated with these faded memories, they were able to resurrect the activity patterns that had occurred when participants initially focused their attention on these items. This, in turn, caused them to remember these stimuli, even though they were not cued to do so.

While the researchers can’t explain exactly what’s going on here, they suspect that some memories are stored via actively-silent” mechanisms, whereby information is somehow held in the synapses between neurons, even when these neurons are not active.

 

儘管如此,這些實驗參與者還是可以回想起那些被遺忘的物體,這指出這些關於遺忘物體的記憶還是存在於他們記憶的某處,雖然沒有神經活動顯示他們有記憶這些物體。研究主筆人Bradley Postle解釋:「人們以為神經會一直活化好讓某些事物一直存在於記憶中。但是我們看到人們記得一些東西,而神經卻沒有活動。」

 

這份研究的作者也發現,用磁刺激與消逝記憶相關的大腦皮層,他們可以再度活化實驗參與者專注於物體時的大腦活動模式。也就是說,這樣他們記得這些刺激,但是他們根本不知道自己有這樣做。雖然研究人員無法完全解釋這個現象的原因,他們認為有些記憶是由「活化但沈默」的機制來儲存,資訊由神經間的突觸保存,即使神經病沒有活化。

 

 

來源:iflscience