4. Brain Research

It is only comparatively recently that the brain has been regarded as the main coordinator of all of the body’s activities. Because of its well-protected position within the cranial cavity, the brain was the last of the body’s organs to be exposed and dissected. Because the abdominal organs were the easiest to reach, they were the first to be discovered and described. Since the liver was believed to be the largest organ and the one most richly supplied with blood, it was the first organ to be considered the seat of the mind and soul. Later the heart was assigned this function, and this notion still persists to some degree, especially in songs and poetry.

4、脑研究

    比较而言，只是在最近，脑被认为是整个身体活动的协调器。由于它在颅腔内的位置被保护的很好，因此脑是人体中最后被展示和解剖的器官。因为，腹部器官最容易触及，因此它们首先被发现和描述。由于肝脏曾被认为是最大的器官，而且是供血最丰富的器官，因此人们认为它是精神和灵魂的所在地。后来，心脏又被赋予了这种功能，而这一想法在某种程度上依然存在，尤其是在歌曲和诗歌中。

Yet prehistoric men must have had some idea that the cranium had a connection with illness, especially emotional illness. They frequently practiced trephining (or repanning) which consisted of boring holes in the skull, presumably to let demons or evil spirits escape.

然而，史前的人类一定知道头盖骨与疾病有关，尤其是与情绪的疾病有关。他们经常用环锯在头骨上钻孔，大概是想让恶魔或幽灵逃出来。

According to the Greek philosopher Plato (c. 428-348 B. C.), the brain was the seat of reasoning because it was nearly spherical, which he considered to be the ideal shape. Hippocrates assigned not only thought to the brain but also emotion even though he had no experimental proof. Herophilus (about 300 B. C.), in dissecting brains of dead criminals and animals, found the fluid-filled cerebral ventricles and thought that from these all the functions of the body were regulated. Although the excellent dissections and drawings of Andreas Vesalius greatly increased man’s knowledge of human anatomy, Vesalius was also responsible for perpetuating the erroneous theory that nerves are hollow tubes that convey a “nervous fluid” supplied by the brain.

根据希腊哲学家柏拉图（公元前428年至348年）的观点，脑是推理的场所，因为它差不多是球形的，他认为那是理想的形状。甚至在没有任何实验证据的情况下，希波克拉底不仅将思想赋予了脑，而且也将情绪赋予了脑。希罗菲卢斯（大约公元前300年），在解剖死亡罪犯和动物的脑时发现了充满液体的脑室，并认为身体的所有功能都是由脑调节的。尽管安德雷亚斯·维萨里出色的解剖与绘图曾极大地增加了人类对人体解剖学的知识，但维萨里也要对一直以来神经是由脑传递“神经液体”空心管的错误理论负责。

Not until the mid-19^th century was there any real departure from this “nervous fluid,” or neurohumoral, theory. At that time the theory of nerve conduction, based on electrical impulses, was introduced by Albrecht von Haller. However, it was not until highly sensitive galvanometers were invented that real proof of a hypothesis of electrical conduction could be obtained. Even then, it was difficult to explain the slower velocity of the nerve impulse compared to that of the conduction of an electrical current along a wire. A possible explanation for this difference came when Otto Loewi, in 1921, postulated a chemical transmission of the nerve impulse. This theory has since been supported by much scientific evidence.

直到19世纪中期人们才真正从这种“神经液体”，或叫神经元介质的理论中摆脱出来。当时，阿尔布雷希特·冯·哈勒基于电脉冲引入了神经传导理论。然而，直到发明出高灵敏的电流计时才获得了电脉冲假设的真正证据。即使那样，仍很难解释神经脉冲比电流沿导线传导速度慢的问题。对这种差别的一种可能解释来自奥托·勒维于1921年假设了一种神经脉冲的化学传递。此后，这种理论得到了很多科学证据的支持。

Present-day brain research may generally be divided into THREE basic fields of study. One is concerned with discovering the functions of different areas of the brain and how these areas affect one another. The second field of study is concerned with the biochemical nature of the brain, analyzing the brain’s chemical makeup and studying how it is affected by various chemicals and drugs. The THIRD aspect of brain research deals with the nature of consciousness and is based on a psychological approach to the brain’s functioning.

现代的脑研究通常可分为三个基础的研究领域。一个是涉及发现脑的不同区域的功能和这些区域是如何相互影响的。第二个研究领域涉及脑的生物化学性质，分析脑的化学组成，并研究它是如何受到各种化学和药物影响的。脑研究的第三个方面涉及意识的本质以及基于对脑的运作的心理学方法。

STUDIES OF BRAIN FUNCTION

In the early 19^th century, the German physician Franz Gall popularized the study of phrenology. According to this school of thought, certain protuberances, or bumps, on the surface of the skull indicated certain areas of the underlying brain that were concerned with intellectual functions. Although this approach to cerebral localization was inaccurate, it may have stimulated scientists to find better method of brain study. Gross anatomical studies of the brain gave little information as to localization of brain functions, and microscopic studies yielded only the information that there are many different types of cells in the brain and that the cells in the cerebral cortex are arranged in layers.

对脑功能的研究

在19世纪早期，德国医生弗朗茨·加尔推广了对颅相学的研究。根据这一学派的观点，头骨表面的某些突起或隆起显示了在脑下面的某些区域与智力功能有关。尽管这种大脑定位的方法并不准确，但它可能促进了科学家寻找更好的脑研究的方法。对脑的粗略解剖研究在脑功能定位方面提供的信息不多，而且显微镜的研究也只获得了在脑中有许多不同类型的细胞，以及在大脑皮层中细胞是按层排列的信息。

One of the greatest advances in the study of brain functioning was the introduction of electrical charges to stimulate areas of the cerebral cortex. This technique, developed by the German scientists Eduard Hitzig and Gustav Frisch about 1870, led to the discovery that the electrical stimulation of certain regions of the cortex causes specific sensory and motor responses. Most of the earliest electrical stimulation studies were conducted on animals, but later they were performed on human patients during brain surgery. These patients could report different sensations as various brain areas were stimulated, and movements in various muscle groups could be observed as different areas were stimulated. Although the results of these studies showed some variation from time to time, scientists were able to make fairly accurate maps of the cerebral cortex. One of the major problems facing researchers, however, was that the stimulation of one area on the brain’s surface excited many neurons in addition to those directly under the brain’s surface. Thus, the procedure had limited accuracy, even for areas near the surface. Another problem, observed by the English physiologist Edgar Douglas Adrian, was the brain never reacts twice in the same way; its electrical activity varies according to the subject’s age and state of alertness.

在脑功能的研究中最伟大的进步之一是引入了电荷来刺激大脑皮层的区域。这项技术是由德国科学家爱德华·希兹格和古斯塔夫·弗里希大约在1870年开发的，这使他们发现，对大脑皮层的某些区域的电刺激会引起特定的感觉和运动反应。大多数最早的电刺激研究都是在动物身上进行的，但后来在脑部手术中电刺激被运用于人类病患。当脑的不同区域受到刺激时，这些患者都可以描述不同的感觉，而当不同的区域受到刺激时也会观察到不同肌肉群的运动。尽管这些研究结果有时会出现一些变化，但科学家已能够绘制出相当精准的大脑皮层图。然而，研究人员面临的主要问题之一是，除了那些直接在脑表面下的神经元外，刺激脑表面的一个区域会激发许多神经元。因此，即使对那些靠近表面的区域，该过程的准确性也有限。由英国生理学家埃德加·道格拉斯·阿德里安观察到的另一个问题是，脑从不会以同样的方式做出两次反应；根据实验对象的年龄和清醒状态，其电活动是不同的。

During the 20^th century technological advances, especially in electronics, greatly improved the accuracy of electrical experimentation. The developments of new electrodes permitted scientists to measure and control the frequency, strength, and duration of the stimuli, and the recording apparatus was also greatly improved. These new electronic devices led to the discovery that when electrical stimulation is applied to the reticular formation an alert or “arousal” pattern is noted on the EEG recording. It was also found that if electrodes are placed in an area of the thalamus or hypothalamus, a typical EEG sleep pattern is produced and the subject falls asleep. After further stimulation of the reticular formation, the subject is awakened. Thus, active arousal and sleep centers were found.

在20世纪中技术的进步，尤其是电子设备的进步极大地促进了电实验的准确性。新电极的发展允许科学家测量和控制频率、强度和刺激的持续时间，而且记录仪器也得到了很大改进。这些新的电子设备使人们发现，当电刺激应用于网状结构时，在EEG的记录上会记录一种报警或“唤起”模式。人们还发现，如果在丘脑或下丘脑的一个区域放置电极，就会产生一个典型的EEG睡眠模式，而且实验对象会入睡。对网状结构进一步刺激后，就会唤醒实验对象。因此，人们便发现了主动唤醒和睡眠中枢。

By the use of this same technique, the sites of origin of various other activities as well as emotions have been determined. The stimulation of areas of the hypothalamus produces rage. In certain other sub-cortical areas, stimulation produces pleasure, whereas when the electrode is moved a distance of a single cell, a sensation of pain is produced.

通过使用这种相同的技术，便查明了各种其它活动和情绪的起源地点。刺激下丘脑的区域会产生狂怒。在某些其它的下皮质区域，刺激会产生快乐，而当将电极移动一个单细胞距离时，就会产生疼痛的感觉。

Probably the most important recent advance in the study of brain stimulation was the development of microelectrodes with tips as tiny as one-millionth of an inch in diameter. These electrodes have made it possible for scientists to stimulate or record impulses from a single cell. In addition, special micromanipulators allow these minute electrodes to be placed deep inside the brain, reaching areas that could not previously be studies with the larger electrodes.

在脑的刺激研究中，可能最重要的进步是尖端直径仅有百万分之一大小微电极的发展。这些电极为科学家刺激或记录单细胞脉冲成为了可能。此外，特定的显微操作器允许将这些极小的电极植入脑的深处，到达以前更大的电极无法研究的区域。

BIOCHEMISTRY OF THE BRAIN

The rapid rise of the science of biochemistry in the 20^th century has greatly influenced fundamental research into the chemical nature of the entire body. When it became apparent that psychic change could be produced by certain glandular disorders, especially those of thyroid deficiency, and that an improvement in mental illness sometimes followed electric shock therapy, or that convulsions or coma could be produced by the administration of metrazol or insulin, new interest was generated in the chemistry of the brain.

脑的生物化学

生物化学科学在20世纪的迅速崛起，极大地影响了整个人体化学性质的基础研究。当某些腺体的紊乱会明显地引起精神变化时，尤其是那些甲状腺缺乏的人，或者使用了强心剂或胰岛素可能引发的抽搐或昏迷，引发了人们对脑化学新的兴趣。

Research in biochemistry had made it possible to analyze the body’s main chemical structure and function. The techniques for this analysis are known and used by most hospital laboratories. It follows, therefore, that these techniques should be extended to include analysis of the chemical structure and function of the brain. Since the mid-1940’s, this research has been going forward at an accelerating pace.

生物化学的研究使分析人体的主要化学结构和功能成为了可能。大多数的医院实验室都了解并使用了这项分析技术。因此，可推断这些技术应该已扩展到包括对脑的化学结构和功能的分析领域。自20世纪40年代中期开始，这项研究已在加速进步。

Through biochemical studies it has been found that brain cells, like other body cells, consist largely of carbohydrates, lipids, and proteins. Lipids are especially abundant in the brain since they are one of the main components of myelin proteins make up about 90% of the brain’s dry weight. Some of these proteins are nucleoproteins, which are composed of nucleic acid molecules. In the brain cells, as well as all other cells of the body, nucleoproteins regulate all of a cell’s activities and play an important role in cell reproduction and heredity. All proteins other than nucleoproteins are made up of small units known as amino acids. It has been found that there are about 20 different kinds of amino acids in the body, and that by linking together in various ways they form all of the body’s proteins.

通过生物化学研究，人们发现，像人体的其它细胞一样，脑细胞主要由碳水化合物、脂类和蛋白质组成。在脑中脂类尤其丰富，因为它们是髓磷脂蛋白的主要成分之一，约占脑净重的90%。其中的一些蛋白质是由核酸分子组成的核蛋白。在脑细胞以及身体的其它细胞中，核蛋白调节细胞的所有活动，并在细胞繁殖和遗传中起重要作用。除了核蛋白外，所有的蛋白质都是由称为氨基酸的小单位组成。人们发现人体中大约有20种不同种类的氨基酸，而且以各种方式相连，它们构成了人体所有的蛋白质。

Amino Acids.  Through studies of brain biochemistry, researchers have discovered that certain amino acids influence the brain’s functioning. For example, an excess of one amino acid, phenylalanine, is responsible for a type of mental deficiency known as phenylketonuria, or PKU.

氨基酸。通过对脑生物化学的研究，研究人员发现某些氨基酸影响脑的功能。例如，一种氨基酸，苯基丙氨酸，过量会导致一种称为苯丙酮尿症，或PKU的智力缺陷。

Glutamic acid, which has the highest concentration of any amino acid in the brain, is rapidly metabolized by brain enzymes, suggesting that this amino acid has a close relationship to glucose metabolism, the most important of the brain’s metabolic processes. It has been found that glutamic acid can substitute for glucose as fuel for the brain if the blood’s glucose content is lowered. Unconfirmed reports have appeared regarding the beneficial effects of glutamic acid in the treatment of certain types of epilepsy, mental deficiency, schizophrenia, and alcoholism.

谷氨酸，是脑中所有氨基酸中浓度最高的，脑中的酶会迅速将其代谢，这表明这种氨基酸与最重要的脑代谢过程的葡萄糖代谢密切相关。人们发现，如果血糖含量降低，那么谷氨酸可以代替葡萄糖作为脑的燃料。关于在治疗某些类型的癫痫、智力缺陷、精神分裂症以及酗酒中谷氨酸的有利作用已出现了一些未经证实的报告。

Another amino acid, tryptophan, is not only essential in the diet as a builder of proteins, but two of its metabolic products have great importance to the normal functioning of the brain. The first of these products to be discovered was nicotinic acid (niacin). A lack of nicotinic acid brought about by a deficiency of tryptophan in the diet is the cause of pellagra. Pellagra is characterized not only by skin eruptions and diarrhea, but also by mental deterioration and death in its later stages. Another metabolic product of tryptophan, serotonin was first synthesized in 1951 and has since around great interest in many fields of medicine. Serotonin occurs chiefly in the lining of the stomach and in the blood. When blood platelets break up, as in blood clotting, they release serotonin, which then causes a constriction of the small blood vessels and thus helps check further bleeding. Serotonin is also found in various nerve tissues, especially in the hypothalamus. Scientists working with cats have found that when serotonin-containing cells in the hypothalamus are destroyed, permanent insomnia results. Thus, serotonin seems to play an important role in nerve functioning. This is further substantiated by the fact that when cats are given drugs that increase the amount of brain serotonin, they sleep much more than normal cats, but when they are give drugs that decrease the amount of serotonin in the brain, they stay awake continually.

另一种氨基酸，色氨酸，不只是在饮食中作为一种蛋白质的构建者必不可少，而且它的两种代谢产物对脑的正常功能也是必不可少的。这些产物第一个被发现的是烟酸（尼克酸）。饮食中由于缺乏色氨酸引起的缺少烟酸是糙皮病的原因。糙皮病的特征不仅是皮疹和腹泻，还会导致精神衰退和在后期的死亡。色氨酸的另一种代谢产物，血清素在1951年首次被合成，此后在许多医学领域产生了极大的兴趣。血清素主要出现在胃内膜和血液中。当血小板破裂时，作为血液中的凝血，它们会释放血清素，然后引发小血管收缩，从而有助于抑制进一步出血。在各种神经组织中，尤其是在下丘脑中也发现了血清素。研究猫的科学家发现，当下丘脑中含有血清素的细胞被破坏时，会导致永久性失眠。因此，血清素在神经功能中似乎起着重要作用。事实进一步证实，当给猫服用增加脑中血清素含量的药物时，它们会比正常的猫睡觉更多，但当它们服用降低脑中血清素含量的药物时，它们会一直醒着。

Research on serotonin has revealed that this substance may also play an active part in producing migraine headaches. During migraine attacks, most of the patients tested were found to have an average drop of 60% in the level of serotonin in their blood. The presence of serotonin in various regions of the brain has also stimulated investigations of the possible connection between serotonin and various mental diseases, and it has been found that the concentration of serotonin varies with the administration of various tranquilizer and antidepressant compounds. There is also strong evidence, even though it is as yet circumstantial, that serotonin may act as a chemical transmitter of nerve impulses.

对血清素的研究表明，这种物质还可以在出现偏头痛中起积极作用。偏头痛发作时，发现受试的大多数患者在他们血液中的血清素水平会平均下降60%。脑中各区域存在的血清素也刺激了在血清素与各种精神疾病之间可能存在联系的调查，而且研究发现，血清素浓度随服用各种镇定剂和抗抑郁化合物而变化。还有更强的证据，即血清纯素可以作为神经脉冲的一种化学神经传递素，尽管它还只是间接证据。

                                   J. EDWARD TETHER, M. D.

                             Indiana University Medical Center

                                    And School of Medicine

                                  J. 爱德华·特瑟，医学博士

                                印第安纳大学警觉中心与医学院

                                                                              2023年4月8日译

（译者注：该词条部分位列《大美百科全书》1985年版，第4卷，第428页至430页）