How does alcohol cause blackouts? - Shannon Odell

譯者: 楊佳穎 118-30 審譯者: Zoe Walmsley

In 1969, Dr. Donald Goodwin gathered a group of study participants

1969 年，唐納德‧古德溫博士 召了一群人參與實驗，

and asked them each to recall the object he'd shown them two minutes prior.

然後他問兩分鐘前 他給他們看的東西是甚麼。

The twist?

這是甚麼把戲？

All the participants were very intoxicated.

所有參與者都喝得非常醉，

Despite this, most could pay attention to the task

儘管如此，大多數人 還是能專注於任務，

and correctly name the toy they had just seen.

並正確說出方才看見的東西是甚麼。

Yet, when Donald asked them to recall that object a mere 30 minutes later,

然而，等 30 分鐘之後， 唐納德再問同一個問題時，

half the participants drew a blank,

卻有一半的人腦中一片空白，

having “blacked out” the earlier moment entirely.

因為稍早的記憶已經完全「斷片」了。

This study illustrates the strange and somewhat selective effects

這項研究顯示出

酒精對大腦產生某種 不可思議且具選擇性的作用

alcohol has on the brain.

Many intoxicated people can perform complex tasks

許多酒醉的人可以執行複雜的任務，

like holding a detailed conversation or navigating a walk home.

例如進行深度的對談， 甚至找到回家的路。

Yet for those experiencing what is known as a blackout,

然而，對於那些喝到「斷片」的人，

the memory of these events is quickly forgotten.

這些記憶很快就煙消雲散。

So how does alcohol cause these memory lapses?

所以酒精是如何造成這種記憶喪失的？

First, let's identify the culprit.

讓我們先找出罪魁禍首。

While a single drink often contains hundreds of different chemical compounds,

即使一杯飲料通常 含有上數百種不同的化合物，

ethanol is responsible for alcohol's effects on the brain.

乙醇卻是酒精影響大腦的主因。

Ethanol is lightweight and lipophilic,

乙醇質輕且具親脂性，

meaning its structure easily dissolves into fats,

意味著其結構容易與脂肪結合，

like those in the membranes of the outer blood-brain barrier.

例如腦血管屏障最外層 那個薄膜中的脂肪。

Once inside the brain, ethanol’s unique structure

一旦進入腦部，乙醇本身獨特的構造

allows it to bind to, interact, and affect many different neuronal receptors,

能讓它與不同的神經元受體 結合、發生作用及影響，

impairing pathways that allow you to make careful decisions, control your impulses,

進而削弱平常幫我們 謹慎決策、控制衝動、

and even manage your motor skills.

管理動作技能的神經傳導路徑。

And the networks that control memory seem to be especially sensitive

而掌管記憶的神經網路

似乎對酒精的影響特別敏感。

to alcohol’s effects.

Typically, information about your surroundings is taken in

通常與周遭環境相關的訊息

由感官接收並傳送至大腦。

by your sensory organs and sent to the brain.

Neurons transfer this information to one another

神經元負責訊息的傳遞工作，

via chemical messengers called neurotransmitters,

透過所謂神經傳遞質的化學物質，

which are released by one neuron and received by receptors at another.

從一個神經元傳送到另一個神經元。

When a neurotransmitter binds to a receptor,

當神經傳遞質與另一個 神經元的受器結合，

it unlocks an internal channel, allowing small ions to flow into the cell.

一條內部通道就會打開， 讓離子流入細胞內。

If enough ions enter the cell, the neuron fires,

當足夠的離子進入細胞內， 神經元就會產生脈衝，

sending the signal forward.

將信號向前傳遞。

Through this process, different regions of the brain

經由這個過程，

不同的腦區能在幾毫秒內彼此溝通，

can communicate with one another in milliseconds,

creating our moment-to-moment understanding of the world.

建構出我們對世界每時每刻的理解。

But ethanol interacts with receptors,

然而，乙醇一旦與神經元受器互動，

making it harder for neurons to communicate.

就會讓神經元間的溝通困難。

While compromised, the brain is still able to transfer information,

儘管受到損害，大腦仍舊能傳遞訊息，

which is why many intoxicated people seem somewhat capable

這就是為何許多人喝醉後 還是能夠執行簡單的任務。

of performing basic tasks.

In other words, brain function is highly impaired,

換句話說，雖然大腦的功能嚴重受損，

but not completely broken.

但並未完全崩潰。

But memory storage is a different story.

不過記憶的儲存則另當別論了。

The transfer of moment-to-moment understanding

每時每刻的理解轉成記憶的過程

to something we can remember is thought to depend on a process

取決於 LTP ： 長期增益效應機制。

called long-term potentiation, or LTP.

LTP happens throughout the brain,

LTP 作用的範圍包含全部的腦區，

but is especially important in learning and memory regions,

但最重要的是在學習與記憶區域，

like the neocortex and the hippocampus.

例如新皮質及海馬迴。

During LTP,

在 LTP 過程中，

the firing of a neuron triggers physical changes to its structure.

神經元產生的脈衝 促成其本身結構上的改變。

For example, more receptors may be moved to the cell's surface,

比如說，可能會有更多受器 移動到細胞表面，

making the neuron more sensitive to future signaling from its neighbors.

導致神經元對來自 鄰近細胞的信號更敏感。

These physical changes increase the likelihood that a cell

這些結構的變化

讓細胞在同一個連結點 產生脈衝的機會提高，

will fire again at that connection,

strengthening the wiring between neurons.

進而強化神經元之間的連結。

And through this stronger connection,

經由這種更強的連結，

it's thought that a stable memory is formed.

更穩定的記憶也因此形成。

Yet studies suggest that ethanol has a unique ability to disrupt LTP,

然而，研究指出乙醇 有某種能力去干擾 LTP，

blocking the physical changes needed for memory formation.

阻斷形成記憶所需的構造上的變化。

So, while moment-to-moment information is encoded and understood,

因此，即使每一瞬間的訊息 皆被編碼、理解，

the storage of that information is blunted,

貯存訊息的功能卻被削弱了，

resulting in a blackout.

從而導致記憶的斷片。

Of course, not all levels of drinking result in blackouts.

當然不是只要喝酒就會造成斷片。

They happen when the concentration of alcohol in the blood, or BAC,

只有當血中的酒精濃度..... BAC 超過一定水準，

exceeds a certain level, approximately 0.16.

大約 0.16 的時候才會發生，

But there’s no magic number.

但這個數字也不是絕對，

At slightly lower BACs, brownouts, or the spotty memory of events, can occur,

因為較低的 BAC 數值 仍有可能導致斷斷續續的記憶，

as some neurons continue to function properly while others fail.

因為即使部分神經元無法運作， 一些還繼續正常運作。

And drinking too much can cause a person to pass out altogether.

而且喝酒過量還能讓人完全昏迷。

Other factors like dehydration level, genetic differences, medications,

其他如身體脫水程度、 基因差異、服用藥物等因素，

and even how much you’ve eaten can affect the likelihood of a blackout.

甚至你吃多少食物 都可能影響發生斷片的機率。

And teenagers appear to be especially vulnerable

而青少年似乎又特別脆弱，

due to the substantial changes in brain development during those years.

因為腦部正經歷青春期時 腦部發育的巨大變化。

Alcohol’s short-term effects usually don’t last longer

酒精的短期影響通常不會長過

than the time it takes for their body to metabolize it, or about a day.

人體新陳代謝所需的時間， 通常一天左右。

But repeatedly over-drinking can damage neurons and permanently impair memory.

然而，長期酗酒除了扼殺 神經元及永久記憶力，

It can also harm other organs like the liver,

還會危害其他器官，例如肝臟.....

which works overtime breaking down alcohol.

肝臟會為了代謝酒精而過勞。

After all, experiencing a blackout or witnessing others

總而言之，無論是自己發生過斷片，

或是目睹他人 處於這種狀態，

in this compromised state

can be a lot for your mind and body to process.

都會對你的身心造成極大的負擔。