| Text
1
Are Dreams as Vital
as Sleep?
by Roger Louis
Can dreams be controlled at our own
will? Is dreaming the ability of all animals? How do
the deaf-mutes and the mentally disabled dream? The
following article discusses these issues.
Sooner or later biologists were bound
to investigate one of the brain's most mysterious functions,
probably the least tangible and the least comprehensible
function of the body, dreaming.
Just a few years ago we thought that
Freud, when he took the keys to the city of dreams
away from the philosophers and poets, had given them
once and for all to the psychologists and
psychiatrists.
But now biologists, biochemists and neuropsychologists
are invading what used to be thought an exclusive preserve.
One of these is a Frenchman, Dr. Michel
Jouvet, whose research at the medical school of Lyons
is internationally recognized as authoritative and on
the same plane as that of Professor Nathaniel Kleitman
in the United States, which has been continued since
1960 by one of his colleagues, Dr. William Dement.
It was more or less by chance that Dr.
Jouvet became interested in dreams in 1958, or rather
it was the logic inherent in any experimental work that
stimulated his curiosity.
"I was interested at that time in confirming
Pavlov's theories of conditioning, using cats as test
animals," he told us. "We had put electrodes in the
muscles of their paws in order to check on certain
movements."
"During their sleep we noted an unexpected
phenomenon that occurred sporadically—the complete
disappearance of muscular tone, sometimes lasting for
several minutes, after which muscular tone reappeared
while the animal continued to sleep.
"We thought of all possible theories
to explain this phenomenon. It even occurred to us that
it might be connected with the very special role that
whiskers play in the cat, and we actually tried cutting
them off to see whether this might have some effect.
Only after a long period of groping, did we realize
that there was a possible correlation with dreaming."
"From that moment our research was directed
towards the physiological study of sleep, especially
towards what we now call its paradoxical phase. This
corresponds to the period in which an animal or a person
dreams."
"This research was carried out in collaboration
with Kleitman and Dement in the United States, among
others. In a very short time we were able to collect
an extraordinary amount of information and numerous
records."
"We might begin with the most basic
points. By mere physical examination of a person or
an animal who is sound asleep, we can now tell whether
he is dreaming or not; better yet, we can identify,
to within one second, the instant he begins to dream
and the instant his dream ends."
"We have three basic physiological criteria
for this finding, and they are now accepted by all
neurophysiologists:
1. Virtually complete disappearance
of muscle tone.
2. Rapid eye movements (hence the term
REM sleep), which seem to be without purpose.
3. Characteristic brain waves on the
electroencephalogram, quite different from those recorded
in deep sleep and very similar to those recorded in
the waking state. Discovery of this tracing gave rise
to the term "paradoxical phase," which we apply to sleep
in the dreaming state.
"We can also state that the average
adult dreams about twenty per cent of the time he is
asleep, in a number of separate dreams. Each dream episode,
about twenty minutes, is preceded by a period of deep
sleep, indicated on the encephalographic record by typical
long waves.
"While we are talking statistics, we
might add that the newborn infant dreams much more than
the adult—fifty percent of his sleeping time—and
this applies to all mammals.
"I might also point out that the capability
for dreaming is not an attribute of all animal species.
In the evolutionary scale it first appears with birds
and with them only to a limited degree—about point
five percent of their sleeping time. All studies in
reptiles and amphibians (e.g. tortoises) give negative
results—there are no dreams in their sleep.
"This gives a brief summary of recent
findings, which will enable us to make a detailed study
of the problems still confronting neurophysiologists
in the phenomena of dreams as well as in the essential
function of dreaming. We are now convinced that dreams
play an important physiological role, although we are
not yet in a position to say just what that role is.
One solitary cat was crouched on a brick
in the middle of a miniature pool and sleeping peacefully
while an electroencephalograph recorded his brain waves.
"We keep him from dreaming," Dr. Jouvet said, "I just
explained that one of the recognized physiological criteria
of the dream phase in animals is disappearance of muscular
tone. This cat can sleep on his brick, but as soon as
he begins to dream his muscular tone disappears, and
he falls into the water. This at once wakes him up,
he climbs back on his brick, licks himself and goes
back to sleep—but whenever he dreams he falls into
the water again.
"If we continue the experiment for a
week and then put him back in his cage, we observe that
he has such a need to dream that, instead of spending
only twenty percent of his sleep time dreaming, he will
then spend forty percent of it or more. A kind of compensatory
mechanism exists somewhere in his nervous system.
"For this reason we think that dreaming
is not a pointless phenomenon that occurs every time
the nervous system goes into free wheeling, but that
it reflects a specific activity of the brain and forms
an essential part of a process. As to what the process
is, that is what we are trying to discover.
"In recent times we have made great
progress in localizing the centers responsible for the
phenomena that accompany dreaming activity. At first
we had to proceed by surgical guesswork, successively
removing various parts of the brain stem of our experimental
animals in order to observe any disturbance in their
sleeping behavior.
"Sleep itself is a highly complex phenomenon,
and it had not yet been decided whether there is a brain
center responsible for sleep or whether simple inhibition
of the waking centers is what causes it.
"However, we have succeeded in precisely
pinpointing the centers responsible for the two principal
characteristics of dreaming activity: first, rapid eye
movement, which we call phase phenomenon and second,
the blocking of muscular tone, which is called a tonic
phenomenon.
Cats in a state of hallucination
"Taken together, these two centers
are about the size of a pea. They are located very close
to one another, but we can influence either one at will
by different techniques. The center controlling muscular
tone, which is no bigger than a grape seed, lives his
dreams. The powerful blockade of muscular tone is no
longer effective, so that the sleeping and dreaming
animal carries out all the movements that correspond
to the action of his dream. An innocent bystander would
get the impression that he was wide awake and perhaps
dangerous, but in actual fact none of his actions or
gestures corresponds to the outside world in which he
is moving. He is asleep and he acts only in accordance
with the fantasies that are passing through his brain.
He is living in an imaginary world—he is hallucinating.
"As soon as he wakes up, his behavior
will become quite normal.
"In this experiment you can appreciate
the importance of this center: its role in dreaming
is primordial. Work is now in progress to study a possible
correlation between these hallucinatory states and certain
mental illnesses.
You might think that sleepwalking would
be due to improper functioning of this center, but recent
experiments have shown that this phenomenon occurs not
during dream periods but in the half awake. People may
also talk at this level of sleep—not during dreams.
"Another related question is whether
the weightlessness experienced in cosmic flights may
not have unexpected and undesirable effects upon the
astronauts insofar as it creates a state equivalent
to the absence of muscular tone. It is not a coincidence
that the physician chosen to participate in the first
trip to the moon planned by the Americans is a specialist
in sleep.
Dreaming can be regulated at will
"But study of
the biochemistry of the phenomenon associated with dreams
will probably lead to the most fascinating results,
and gives us scope to formulate the boldest hypotheses.
In the past few years, chemistry has occupied a solid
position in the study of biologic phenomena.
"Neurohumoral processes of the brain
are immensely intriguing to present-day research men,
who expect to find in them the key to the most complex
phenomena.
"Hyden's studies, to cite one example,
convincingly show that biochemistry can open a new point
of view on biologic phenomena as complicated as memory.
This is also true of our studies on dreaming. The REMs,
which appear to be at the origin of the dream stage
of sleep, can be blocked or amplified by chemical inhibitors
or precursors. In other words, it is possible, by means
of specific drugs, to deprive an animal of dreams entirely
or to increase them to sixty percent of the time he
sleeps.
"I can offer only one hypothesis, which
is directing our study. It is difficult to verify in
the present state of our knowledge, but so far nothing
contradicts it. Here it is: dreaming activity is inseparable
from other activities of the nervous system. There are
not separate states of waking, sleeping, dreaming; these
phenomena make up a continuum that is characteristic
of certain creatures. In the waking state our nervous
system, particularly the brain, perceives a certain
number of sensations and records or memorizes them in
chemical form by synthesizing molecules of specific
proteins. This synthesis takes place through a highly
complex process.
"This conversion of incoming information
into a coded chemical schema is not instantaneous. The
chemical factory of our brain needs time to store, select
and classify information according to a code that is
still to be defined. We might say that the waking state
is equivalent to recording information on a dictaphone;
during deep sleep this information is typed out; and
in the course of dreaming, each page or each sentence,
or even each word is classified in a file cabinet along
with previous information that is stored away in terms
of a careful, previously-established code.
"This would explain why our dreams contain
numerous images corresponding to impressions received
in the waking state, and also why some of this information
is completely deformed or symbolized. This synthesis
of events of the day in dreams would imply a "trituration"
of information, together with a review of previous information
already classified and coded.
"This hypothesis would also explain
why newborn infants and young animals have a high percentage
of dreaming time—more than twice as much as adults.
"I must admit that this hypothesis,
although it links dreams to learning and memory, encounters
a number of obstacles, it fails to explain why this
function suddenly appears in the evolution of species
with the bird, to be magnified in a kind of explosion
with the mammals.
"We must wait some years for the neurophysiologists
to carry out further experiments and to interpret them;
but it seems to be already well-established that dreams
have once and for all left the world of unreality for
the world of the laboratory."
(1894 words)
TOP
|
课文一
梦与睡眠一样重要吗?
罗杰·露易丝
我们是否能根据自己的意愿来控制梦境?所有动物都能做梦吗?聋哑人和弱智者怎样做梦?下面这篇文章将讨论这些问题。
生物学家们迟早会去探究梦这个大脑最神秘的一个功能，可能是最难以触摸、难以理解的人体功能。
只是在几年以前，我们以为弗洛依德从哲学家和诗人那儿拿走打开梦境之城的钥匙，并将它们永远地留给心理学家与精神分析学家。但现在生物学家，生物化学家以及神经心理学家正在侵入这片曾经被认为是神圣不可侵犯的领地。
他们其中的一位是法国人米歇尔·儒弗博士，他在里昂医学院的研究被国际公认为同美国纳桑尼尔·克莱特曼教授的研究一样具有权威性，处于同一个层面。克莱特曼的研究自1960年以来由他的同事威廉·第门特继续下来。
儒弗博士1958年对梦的研究产生兴趣，这或多或少是碰巧的事情，或者说，是实验性工作内含的逻辑性引发了他的好奇。
“我当时对证明巴甫洛夫的条件理论感兴趣，用猫作为实验动物，”他告诉我们。“我们将电极植入猫爪的肌肉中，来检验某些运动，。”
“在它们的睡眠中，我们注意到了一种断续发生的出人意料的现象——肌肉紧张的完全消失，有时延续几分钟，之后肌肉紧张重新出现，而动物继续睡觉。
“我们想到了用各种可能的理论来解释这一现象。我们甚至觉得猫须的特殊作用可能与这一现象有联系，而且我们实际上试着将猫须剪掉，看这是否起些作用。经过长期的摸索后，我们才意识到这可能与做梦有关。”
“从那时起，我们的研究转向了对睡眠的生理研究，特别是转向了我们所指的反常阶段。这一阶段与动物或人做梦的时期是一致的。”
“这一研究是与美国的克莱特曼和第门特等合作进行的。不久，我们就收集了大量的信息与丰富的记录。”
“我们能从最基本点开始。只需对酣睡中的动物或人进行体检，我们现在就能说出他是否在做梦。进一步说，我们可以在一秒钟时间内确定他开始做梦的时刻与结束做梦的时刻。”
“对这一发现，我们有三条基本的生理学原则，现在已被所有的神经生理学家接受：
1.肌肉紧张性几乎完全消失。
2.似乎没有目的的快速眼动(因此而产生了快速眼动睡眠这一术语)。
3.脑电图上特有的脑电波，与酣睡中记录下来的脑电波完全不同，而与醒着时记录下来的脑电波很相似。这种脑波图象的发现导致了“反常阶段”这一术语的出现，这一阶段是指睡梦状态。
“我们还可以说，一般成人睡眠时间的20%是在做梦，是一系列分开的梦。每一段梦大约延续20分钟，接着是一阵酣睡，以典型的长波显示在脑电记录上。
“谈到统计数据，我们可以补充说，新生婴儿比成人梦得更多——占50%的睡眠时间——这一数据适应于所有哺乳动物。
“我还要指出，做梦的能力不是所有动物种类的属性。在演变量表上先是鸟类具有这一能力，并且只是在有限的程度上——占它们睡眠时间的0.5%。对爬行动物与两栖动物(如龟类)的所有研究结果都是否定的——它们的睡眠中没有梦境。
“这是对最新发现的概述，这些发现使我们能详细研究至今令神经生理学家们苦恼的梦的现象以及做梦的基本功能等问题。我们确信，梦担负着一种重要的生理作用，尽管我们还说不出这一作用到底是什么。
一只孤独的猫蜷缩在小水池中央的一块砖头上，正安详地入睡，同时有一台脑电图仪记录着它的脑波。“我们不让它做梦，”儒弗博士说，“我刚刚解释了，公认的有关动物梦境阶段的生理学标准之一是肌肉紧张性的消失。这只猫可以在砖头上睡觉，但它一开始做梦，肌肉紧张性就消失，它就掉进水中。这使它立即醒过来，爬回到砖头上，舔了舔自己又睡着了——但他一开始做梦，就又掉进了水里。
“如果我们把这一实验持续一星期，然后将它放回笼子，我们观察到它非常需要做梦，会将睡眠时间的40%或更多而不仅仅是20%用来做梦。它神经系统的某些地方存在着一种补偿性机理。
“由于这个原因，我们认为，做梦不是神经系统进入自由运转时出现的毫无意义的现象，它反映了大脑的特定活动，构成某一过程的必然部分。至于这一过程是什么，我们正在探索。
“近来，我们在确定对伴随着睡梦活动的现象负责的神经中枢位置方面，取得了很大的进展。开始时，我们为了观察它们睡眠行为中的任何干扰，不得不进行外科方面的猜测性工作，相继去掉实验动物脑干的不同部分。
“睡眠本身是一种高度复杂的现象，那时还没有确定是否存在一种负责睡眠的大脑中枢，或者说对醒觉中枢的简单抑制是否是引起睡眠的原因。
“然而，我们已成功地、精确地确定了一些中枢的位置，这些中枢负责睡梦活动中的两个主要特点：第一，快速眼动，我们称之为阶段现象，第二，肌肉紧张性的阻塞，我们称之为紧张性现象。
幻觉状态中的猫
“这两个中枢加在一起大约有一粒豌豆大。它们相距很近，但我们可以随意采用不同技术来影响其中的一个。控制肌肉紧张性的中枢不到一粒葡萄核大，却使睡梦现象逼真。肌肉紧张性的严重阻滞不再有效，以致睡梦中的动物做出与它梦境中行动一致的各种运动。一位天真的旁观者可能会有这样的印象，认为他是完全醒着并且可能是危险的，但实际上，他的任何行动或动作都与他行走其中的外部世界不相一致。他在睡眠，而他只是按照头脑中闪现的幻想行动。他活在一个虚幻的世界——他在产生幻觉。
“一旦他醒来，他的行为将变得十分正常。
在这一实验中，你可以体味到这个中枢的重要性：它在梦中的作用是原生性的。对这些幻觉状态与某些精神疾病之间潜在的相互关系的研究现已取得了进展。
你也许会认为，梦游可能是这一中枢功能失调所致，但近来实验显示，这一现象不是在做梦的的过程中发生而是在半醒时发生。在睡眠的这个层次——不是在做梦期间——人们还可以谈话。
“另一个相关的问题是，宇宙飞行中经历的失重现象是否可能对宇船员产生出乎意料、令人不快的影响，以致于它能产生一种类似于肌肉紧张性消失的状态。入选参加美国人计划的首次月球旅行的内科医生就是一名睡眠专家，这并非巧合。
做梦可以随意调节
“但是，生物化学对有关梦的研究将可能导致最为惊人的结果，为我们提供最大胆设想的机会。在过去几年中，化学在生物现象研究中占据稳固的地位。
“大脑的神经元介质过程激起了目前研究人员极大的兴趣，他们期望在这些过程中找到解决最复杂现象的答案。
“以海顿为例，他的研究充分地表明，生物化学能为象记忆这样复杂的生物现象开拓新的视角。我们对做梦的研究也同样如此。似乎是处在睡眠的做梦阶段开始时的快速眼动，却可以受到化学抑制剂或先兆的堵塞或扩大。换言之，采用具体的药物，可以完全剥夺动物的梦境，或者把做梦的时间增加到睡眠时间的60%。
“我只能提供一种指引我们研究的假设。虽然以我们目前的知识状态还难以证明这一假设，但到目前为止还没有与之相抵触的事情。这一假设是：做梦这一活动与神经系统的其它活动不可分离。不存在分开的醒着、睡眠、梦境状态；这些现象构成了某些动物特有的连续体。在醒着状态下，我们的神经系统，特别是大脑，意识到一定数量的感觉，并且通过合成某些具体蛋白质的分子，以化学形式来记录或记忆这些感觉。这种合成在一种高度复杂的过程中进行。
“新的信息转换成代码化学图式不是即刻的。我们大脑中的化学工厂需要时间，按照某种有待确定的规则，对信息进行储存、选择以及分类。我们可以说，醒着的状态等于在口述录音机上录信息；在深睡时，这一信息被打印出来；在做梦的过程中，每一页或每个句子，或甚至每一个字都被分类并与以前的信息一起存入档案柜，以前的信息是根据精确的、预先确立的规则储存起来
。
“这能够解释，为什么我们的梦包含了大量的与醒着状态下接收的印象相一致的意象，或者说为什么有些信息被完全扭曲或符号化。白日发生的事件在梦中的合成可能暗示出一种信息“研制剂”，以及对前面已分类和编码的信息的回顾。
“这一假设还将解释，为什么新生婴儿及幼小动物做梦时间的比例高——高达成人的两倍以上。
“我必须承认，尽管这一假设把梦与学习及记忆力联系起来，它却面临着一系列困难。它不能解释为什么这一功能突然在鸟类演变的过程中出现，在哺乳动物那里爆炸性地扩大了。
“我们必须等一些年，让神经心理学家进一步实验，并对它们进行解释；但有一点似乎已经成立，梦已永远离开非现实的世界，走向了实验室的世界。
返回
|
