The First Digression
Let us assume a brain has been removed from its cranium and placed on a small glass table before us. What we see is a gray mass ridged throughout with deep furrows and raised convolutions. This mass is divided into two hemispheres, left and right, connected by a thick, callous ligament. Superficially this matter—the cortex of the large hemispheres—is of an even gray color; though less than four to five millimeters thick, it consists of an enormous number of nerve cells that form the material basis for all complex psychological processes.
The cortex of the outer sections of the hemispheres is of more recent origin than that of the interior parts. Just below the thin layer of the cortex is the white matter, which is composed of multitudes of closely connected fibers that join separate parts of the cortex, conduct to it stimuli originating at the periphery, and redirect to the periphery reactions that develop in the cortex. On a still deeper level additional sections of gray matter are to be found; these form the subcortical nuclei of the brain, the oldest and most recessed mechanisms of the brain—stations at which stimuli from the periphery terminate and undergo their initial processing.
The brain appears to be uniform and monotonous, but it is the highest product of evolution. It receives, processes, and retains information, sets up programs of behavior, and regulates their execution.
Until quite recently we knew very little about its structure and functional organization. Precise knowledge was rarely to be found in the textbooks, which were filled with vague suppositions and fantastic conjectures that made maps of the brain scarcely more reliable than medieval geographers’ maps of the world.
Owing to the work of such eminent scholars as I. M. Sechenov, I. P. Pavlov, Monakov, Goldstein, and others we now know far more about the human brain. And though our conceptions amount to no more than the most elementary stage of a real science, we have come a long way from the vague surmises and unverified assumptions that characterized the knowledge of previous generations. Precisely because of this information we can analyze more closely the symptoms this patient’s injury produced.
Obviously the superficial impression one has of the brain as a uniform, undifferentiated gray mass is diametrically opposed to the inconceivable complexity and differentiation this organ actually possesses. The gray matter consists of an extraordinary number of nerve cells, neurons, the fundamental units of brain activity. Some scientists estimate there are 14 billion of these; others assume the total is even higher. More importantly, these neurons have a strict pattern of organization: individual areas or “blocks” differ radically in function.
Given the complexity of the problems under consideration, we can simplify the case somewhat by singling out for attention the most important components of the human brain, the three fundamental “blocks” of this amazing apparatus.
The first of these formations might be called the “energizing” or “tonus-regulating” block. It is located at the base of the brain within the upper sections of the brain stem, and in the reticular formation that constitutes the starting point for the brain’s vital activity.
Part of this block, located within the depths of these masses of gray matter, is what the ancients termed the “visual bump” (optic thalamus) though it actually has only a remote connection with visual processes. It is a preliminary station for processing impulses stemming from both metabolic functions in the organism and excitation of the sensory organs. When these impulses, in turn, are conducted to the cerebral cortex, they impart to it its normal state of tonicity and vigor. If the influx of these impulses ceases, the cortex loses its tonicity, the person lapses into a semisomnolent state, and then into sleep. This mechanism “feeds” the brain just as a power source provides for the “feeding” of electronic devices. Insofar as this “energy” block had been left intact in this patient, he was able to remain alert and generally active.
Figure 1
The regions of the brain. The gross anatomy of the human brain is depicted at upper left. The other drawings identify three major blocks of the brain involved in the organization of behavior. The first block (upper right) includes the brain stem and the old cortex. It regulates wakefulness and the response to stimuli. The second block (lower left) plays a key role in the analysis, coding, and storage of information. The third block (lower right) is involved in the formation of intentions and programs.
The second major block of the brain, located in the posterior sections of the large hemispheres, performs a most important function. Since it was precisely a part of this block that the man’s injury had destroyed, we should consider it in greater detail.
The function of this block is not to guarantee the vigor of the cortex, but rather to act as a block for receiving, processing, and retaining information a person derives from the external world. A person perceives thousands of objects, both familiar and unfamiliar. He picks up an endless number of signals from his environment. The reflection these stimuli produce in the retina of the eye is transmitted by very fine nerve fibers to the occipital regions of the cerebral cortex—the visual area of the cortex. At this point a visual image is broken down into millions of component features, for the nerve cells in the cortex of the occipital regions have highly specialized functions. Some distinguish between the finest gradations of color; others respond only to smooth, round, or angular lines; still others to movement from a peripheral point to a center, or a center to a periphery. This section of the cortex, the “primary visual cortex” (located in the hindmost part of the occipital region), is indeed a remarkable laboratory that breaks down images of the external world into millions of constituent parts. It, too, had been left undamaged by this patient’s injury.
Adjacent to this area is another section of the occipital region that specialists term the “secondary visual cortex.” The entire mass of this cortex consists of tiny nerve cells with short offshoots resembling stars (hence termed “stellate cells”). Distributed throughout the upper layers of the cerebral cortex, they combine stimuli transmitted to them from the “primary visual cortex” into complete and intricate complexes—“dynamic patterns.” They convert the individual features of objects perceived into complete, manifold structures.
If one applies an electric shock to the “primary visual cortex” (this can be done during a brain operation and is absolutely painless), glowing points, circles, and fiery tips appear before the person’s eyes. If, however, one applies the shock to any part of the “secondary visual cortex,” a person sees complex patterns or, at times, complete objects—trees swaying, a squirrel leaping, a friend approaching and waving. It has been shown that stimulation of these “secondary” areas of the visual cortex has the power to provoke graphic recollections of the past, such as images of objects. This part of the brain operates as a device for processing and retaining information, and we are indebted to scientists from various countries (Förster of Germany, Pötzl of Austria, Penfield of Canada) for this new and fascinating discovery about the brain’s activity.
Given the complexity of these functions, one can well imagine the serious consequences that follow from an injury to these sections of the cortex. An injury that destroys the “primary visual cortex” of one hemisphere, or the clusters of nerve fibers conducting visual stimuli to it (the latter form a delicate fan within the brain matter and are appropriately termed the “optic radiation”), obliterates part of the field of vision. Destruction of the “primary visual cortex” or the fibers of the left hemisphere results in a loss of the right half of the visual field, whereas damage to this same part of the cortex in the right hemisphere affects the left half of the visual field. Physicians use a cumbersome, awkward term to describe this (“hemianopsia”—loss of half the field of vision). Such a symptom is a reliable indication of precisely which part of the cortex has been destroyed.
An injury to the “secondary visual cortex” produces an even more peculiar syndrome. If a shell or bomb fragment strikes the anterior sections of the occipital area (these are part of the “secondary visual cortex”), a person continues to see objects as clearly as before. However, the small, “stellate cells” no longer function; and it is these that synthesize individual characteristics of objects perceived into complete wholes. Hence, a person’s vision undergoes a bewildering change: he still distinguishes individual parts of objects but no longer can synthesize them into complete images; and, like a scholar trying to decipher some Assyrian cuneiform, can only surmise the total from these separate parts.
Let us assume such a person is asked to look at a picture of a pair of eyeglasses. What is it he sees? One circle, then another, then a cross bar, and finally, two cane-like attachments. His guess is—it must be a bicycle. Such a patient cannot perceive objects, even though he can distinguish their individual features. He suffers from a complex disorder for which physicians use a combined Latin-Greek term—“optical agnosia” (inability to recognize the meaning of visual stimuli).
Cognition, however, is affected by other factors than those described above. After all, we do not simply perceive isolated objects but entire situations; we also note the complex relationships and correspondences between objects, their location in space (the notebook is on the right side of the table, the inkwell on the left; to get to one’s room he first has to turn left in the corridor, then right, etc.). Since objects are arranged within an entire system of spatial coordinates, we can immediately sense where they are located.
The ability to grasp situations, or gauge spatial relationships, involves something far more complex than the perception of figures or objects. Not only our eyes but our motor experience plays a part in this (one can pick up a notebook with his right hand, reach for an inkwell with his left, etc.). Our ability to locate objects in space is further assisted by a special organ in the interior part of the ears—a “vestibular” mechanism which maintains the sense of balance that is so essential for gauging three-dimensional space. Eye movements, too, are closely related to this function, for they can help to gauge the distance from one object to another at a glance and to determine their interrelationship. The organized, combined operation of these various systems is necessary to insure that distinct, consecutive impressions will be recodified into a complete, instantaneous framework.
Naturally, other, more complex sectors of the cerebral cortex affect our simultaneous grasp of spatial relationships. These sectors are adjacent to the occipital, parietal, and temporal areas and constitute one of the mechanisms of the “tertiary” cognitive part of the cortex (at this point it could be termed the “gnostic” part). The function of the latter is to combine the visual (occipital), tactile-motor (parietal), and auditory-vestibular (temporal) sections of the brain. These sections are the most complex formations in the second block of the human brain. In the process of evolution they were the last part of the brain to develop, and only in man did they acquire any vigor. They are not even fully developed in the human infant but mature gradually and become effective by ages four to seven. They are extremely vulnerable and even a slight impairment disrupts their function. Since they consist entirely of highly complex “associative” cells, many specialists term them “zones of convergence” for the visual, tactile-motor, and auditory-vestibular parts of the brain.
It was precisely these “tertiary” sectors of the cortex that the bullet fragment had destroyed in this patient’s brain. Hence, we must consider what symptoms damage to parts of this sector of the cortex (either by shell or bullet fragments or by hemorrhaging and inflammation) can produce.
The person’s visual capacity may remain relatively unimpaired. But if the bullet passes through the fibers of the “optic radiation” and destroys part of these, blind spots occur and an entire part (sometimes one-half) of the visual field disintegrates. A person will also continue to perceive discrete objects (since the “secondary” sectors of the visual cortex have remained intact), to have tactile and auditory sensations, and to discern speech sounds. Nonetheless, a very important function has been seriously impaired: he cannot immediately combine his impressions into a coherent whole; his world becomes fragmented.
He is aware of his own body and senses both his arms and legs, though he cannot tell his right arm from his left. It is impossible for him to figure this out immediately. To do so, he has to locate his arms in terms of an entire system of spatial coordinates, to distinguish left from right. Let us say he begins to make his bed: is he to arrange the cover lengthwise or crosswise? If he tries to put on a robe, how is he to tell the right sleeve from the left? Or, how is he to understand what time the hands of the clock indicate? The numbers “3” and “9” are exactly parallel, except that one is on the right and the other on the left side of the clock. But how does such a person determine “right” and “left”? In short, every move he makes becomes terribly complicated.
Furthermore, the above does not exhaust the range of problems he faces in a “fragmented” world. The “tertiary” regions of the parieto-occipito-temporal cortex of the left hemisphere are intricately linked to one of the most important psychological functions—namely, language.
Over a century ago the French anatomist Paul Broca discovered that an injury to the posterior sectors of the inferior frontal convolution of the left hemisphere results in a disintegration of the “motor images of words,” thereby impairing a person’s capacity to speak. Several years later the German psychiatrist C. Wernicke disclosed that (in right-handed people) an injury to the posterior sectors of the superior temporal region of the same hemisphere damages one’s ability to distinguish and understand speech sounds.
A person works with his right hand, it plays a dominant role in his life. Yet it is the opposite, the left, hemisphere that controls this hand and the faculty for speech, one of the most complex human activities. Language is not simply a means of communication but a crucial part of the entire process of cognition. We use words to designate objects and their location in space (right, left, behind, in front of etc.). Through grammatical constructions we express relationships and ideas. Regardless of how private or abbreviated language may be, it is pivotal to cognition: by means of it we designate numbers, perform mathematical calculations, analyze our perceptions, distinguish the essential from the inessential, and form categories of distinct impressions.
Apart from being a means of communication, language is fundamental to perception and memory, thinking and behavior. It organizes our inner life.
Is it any wonder, then, that destruction of the “tertiary” sectors of the cortex of the left hemisphere produces even more serious consequences than those we have just described? A person with such an injury finds his inner world fragmented; he cannot think of a particular word he needs to express an idea; he finds complex grammatical relationships unbelievably difficult; he forgets how to add or use any of the skills he learned in school. Whatever knowledge he once had is broken down into discrete, unrelated bits of information. On the surface his life may appear no different but it has changed radically; owing to an injury to a small part of his brain, his world has become an endless series of mazes.
One would think that were even a part of this important block destroyed, a man’s life would be devastated entirely. He would be deprived of what is uniquely human, transformed into a helpless invalid, left without a present, or any possibility of a future. Yet there is a third major block of the brain we have not discussed which, in this patient, had remained undamaged.
This block is located in the anterior sectors of the brain, and includes the frontal lobes. It does not affect the tonicity of the cortex; neither does it receive, process, or retain information from the physical world. It is linked to the world solely by means of mechanisms in the second block, and it can function effectively only if the first block has kept the cortex sufficiently nourished and vigorous. The function of the third block is decisively important; it is a powerful apparatus that allows one to form and sustain intentions, plan actions, and carry them through.
Since I have dealt at length with this block elsewhere, there is only one point I need make here: namely, that an injury to the anterior sectors of the brain (including the frontal lobes) produces an entirely different syndrome than the one we have described. Such an injury does not damage a person’s capacity to learn, perceive, or remember. His world remains intact, though his life is indeed pathetic: he is completely unable to form any lasting intentions, plan for the future, or determine the course of his own behavior. He can only respond to signals he picks up from without, but is powerless to convert these into a set of symbols to control his behavior. And since he has no possibility of evaluating his shortcomings, he cannot correct them. He cannot even conceive of what he will do the next minute, much less the next hour or day. Hence, though his past remains intact, he is robbed of any possibility of a future and loses precisely what it is that makes a person human.
In our patient the mechanisms of the third block, the frontal cortex, had been spared, and with them his capacity to recognize his defects and wish to overcome them. He was acutely aware of what it means to be human, and to the extent his strength permitted, worked feverishly to overcome his problems. He suffered intensely, and though his world had been devastated, in the deepest sense he remained a man, struggling to regain what he had lost, reconstitute his life, and use the powers he had once had:
It was depressing, unbearable to realize how miserable and pathetic my situation was. You see, I’d become illiterate, sick, had no memory. So once again I’d try to revive some hope of recovering from this terrible disease. I began to fantasize that I’d get over the headaches and dizzy spells, recover my vision and hearing, remember all I’d ever learned.
Of course people didn’t realize what my situation was really like, they weren’t aware what an enormous effort it had taken just for me to get this far. Still, I want to think I can prove to people I’m not a goner, not a hopeless case, that all I need is to learn to remember and speak again, be able to use the kind of mind I had before I was wounded (a halfway decent one). Once in a while this awful amnesia gets me down but I still hope I can put some sort of life together again, so I don’t want people to think I’m hopeless. I’m trying to realize part of these dreams and gradually do whatever I still can.
I haven’t lost hope I’ll be fit for some kind of work and can be of some service to my country. I believe that. . . .