The River of Consciousness

by Oliver Sacks

  Similar reversals may be seen in many patients with extremely severe Tourette’s syndrome, who can be brought to an almost stuporous halt by the most minute dose of certain drugs. Even without medication, states of motionless and almost hypnotic concentration tend to occur in Touretters, and these represent the other side, so to speak, of the hyperactive and distractible state.

  In catatonia, there may also be dramatic, instantaneous transformations from immobile, stuporous states to wildly active, frenzied ones.*5 Catatonia is rarely seen, especially in our present, tranquilized age, but some of the fear and bewilderment inspired by the insane must have come from these sudden, unpredictable transformations.

  Catatonia, parkinsonism, and Tourette’s, no less than manic depression, may all be thought of as “bi–polar” disorders. All of them, to use the nineteenth-century French term, are disorders à double forme—Janus-faced disorders which can switch incontinently from one face, one form, to the other. The possibility of any neutral state, any unpolarized state, any “normality,” is so reduced in such disorders that we must envisage a dumbbell- or hourglass-shaped “surface” of disease, with only a thin neck or isthmus of neutrality between the two ends.

  It is common in neurology to speak of “deficits”—the knocking out of a physiological (and perhaps psychological) function by a lesion, or area of damage, in the brain. Lesions in the cortex tend to produce “simple” deficits, like loss of color vision or the ability to recognize letters or numbers. In contrast, lesions in the regulatory systems of the subcortex which control movement, tempo, emotion, appetite, level of consciousness, etc., undermine control and stability, so that patients lose the normal broad base of resilience, the middle ground, and may then be thrown almost helplessly, like puppets, from one extreme to another.

  Doris Lessing once wrote of the situation of my postencephalitic patients, “It makes you aware of what a knife-edge we live on.” Yet, in health, we live not on a knife edge but on a broad and stable saddleback of normality. Physiologically, neural normality reflects a balance between excitatory and inhibitory systems in the brain, a balance which, in the absence of drugs or damage, has a remarkable latitude and resilience.

  We, as human beings, have relatively constant and characteristic rates of movement, though some people are a bit faster, some a bit slower, and there may be variations in our levels of energy and engagement throughout the day. We are livelier, we move a little faster, we live faster when we are young; we slow down a little, at least in terms of bodily movement and reaction times, as we age. But the range of all these rates, at least in ordinary people, under normal circumstances, is quite limited. There is not that much difference in reaction times between the old and the young, or between the world’s best athletes and the least athletic among us. This seems to be the case with basic mental operations, too—the maximum speed at which one can perform serial computations, recognition, visual associations, and so on. The dazzling performances of chess masters, lightning-speed calculators, musical improvisers, and other virtuosos may have less to do with basic neural speed than with the vast range of knowledge, memorized patterns and strategies, and hugely sophisticated skills they can call upon.

  And yet occasionally there are those who seem to reach almost superhuman speeds of thought. Robert Oppenheimer, famously, when young physicists came to explain their ideas to him, would grasp the gist and implications of their thoughts within seconds, and interrupt them, extend their thoughts, almost as soon as they opened their mouths. Virtually everyone who heard Isaiah Berlin improvise in his torrentially rapid speech, piling image upon image, idea upon idea, building enormous mental structures which evolved and dissolved before one’s eyes, felt they were privy to an astonishing mental phenomenon. And this is equally so of a comic genius like Robin Williams, whose explosive, incandescent flights of association and wit seem to take off and hurtle along at rocket-like speeds. Yet here, presumably, one is dealing not with the speeds of individual nerve cells and simple circuits but with neural networks of a much higher order, exceeding the complexity of the largest supercomputer.

  Nevertheless, we humans, even the fastest among us, are limited in speed by basic neural determinants, by cells with limited rates of firing, and by limited speeds of conduction between different cells and cell groups. And if somehow we could accelerate ourselves a dozen or fifty times, we would find ourselves wholly out of sync with the world around us and in a situation as bizarre as that of the narrator in Wells’s story.

  But we can make up for the limitations of our bodies, our senses, by using instruments of various kinds. We have unlocked time, as in the seventeenth century we unlocked space, and now have at our disposal what are, in effect, temporal microscopes and temporal telescopes of prodigious power. With these, we can achieve a quadrillion-fold acceleration or retardation, so that we can watch, by laser stroboscopy, the femtosecond-quick formation and dissolution of chemical bonds; or observe, contracted to a few minutes through computer simulation, the thirteen-billion-year history of the universe from the Big Bang to the present, or (at even higher temporal compression) its projected future to the end of time. Through such instruments, we can enhance our perceptions, speed or slow them, in effect, to a degree infinitely beyond what any living process could match. In this way, stuck though we are in our own speed and time, we can, in imagination, enter all speeds, all time.

  * * *

  *1 The very vocabulary of parkinsonism is couched in terms of speed. Neurologists have an array of terms to denote this: if movement is slowed, they talk about bradykinesia; if brought to a halt, akinesia; if excessively rapid, tachykinesia. Similarly, one can have bradyphrenia or tachyphrenia, a slowing or accelerating of thought.

  *2 Disorders of spatial scale are as common in parkinsonism as disorders of time scale. An almost diagnostic sign of parkinsonism is micrographia—minute and often diminishingly small handwriting. Typically, patients are not aware of this at the time; it is only later, when they are back in a normal spatial frame of reference, that they are able to judge that their writing was smaller than usual. Thus there may be, for some patients, a compression of space that is comparable to the compression of time. One of my postencephalitic patients used to say, “My space, our space, is nothing like your space.”

  *3 My colleagues and I presented these results at a meeting of the Society for Neuroscience (see Sacks, Fookson, et al., 1993).

  *4 Ray is described in The Man Who Mistook His Wife for a Hat.

  *5 The great psychiatrist Eugen Bleuler described this in 1911:

  At times the peace and quiet is broken by the appearance of a catatonic raptus. Suddenly the patient springs up, smashes something, seizes someone with extraordinary power and dexterity….A catatonic arouses himself from his rigidity, runs around the streets in his nightshirt for three hours, and finally falls down and remains lying in a cataleptic state in the gutter. The movements are often executed with great strength, and nearly always involve unnecessary muscle groups….They seem to have lost control of measure and power of their movements.

  Sentience: The Mental Lives of Plants and Worms

  Charles Darwin’s last book, published in 1881, was a study of the humble earthworm. His main theme—expressed in the title, The Formation of Vegetable Mould, Through the Action of Worms—was the immense power of worms, in vast numbers and over millions of years, to till the soil and change the face of earth.

  Darwin calculated this effect:

  Nor should we forget, in considering the power which worms exert in triturating particles of rock, that there is good evidence that on each acre of land, which is sufficiently damp and not too sandy, gravelly or rocky for worms to inhabit, a weight of more than ten tons of earth annually passes through their bodies and is brought to the surface. The result for a country of the size of Great Britain, within a period not very long in a geological sense, such as a million years, cannot be insignificant.

  His opening chapters, though, are devoted more si
mply to the “habits” of worms. Worms can distinguish between light and dark, and they generally stay underground, safe from predators, during daylight hours. They have no ears, but if they are deaf to aerial vibration, they are exceedingly sensitive to vibrations conducted through the earth, as might be generated by the footsteps of approaching animals. All of these sensations, Darwin noted, are transmitted to collections of nerve cells (he called them “the cerebral ganglia”) in the worm’s head.

  “When a worm is suddenly illuminated,” Darwin wrote, it “dashes like a rabbit into its burrow.” He noted that he was “at first led to look at the action as a reflex one,” but then observed that this behavior could be modified; for instance, when a worm was otherwise engaged, it showed no withdrawal with sudden exposure to light.

  For Darwin, the ability to modulate responses indicated “the presence of a mind of some kind.” He also wrote of the “mental qualities” of worms in relation to their plugging up their burrows, noting that “if worms are able to judge…having drawn an object close to the mouths of their burrows, how best to drag it in, they must acquire some notion of its general shape.” This moved him to argue that worms “deserve to be called intelligent, for they then act in nearly the same manner as a man under similar circumstances.”

  As a boy, I played with the earthworms in our garden (and later used them in research projects), but my true love was for the seashore, and especially tidal pools, for we nearly always took our summer holidays at the seaside. This early, lyrical feeling for the beauty of simple sea creatures became more scientific under the influence of a biology teacher at school and our annual visits with him to the marine station at Millport in southwest Scotland, where we could investigate the immense range of invertebrate animals on the seashores of Cumbrae. I was so excited by these Millport visits that I thought I would like to become a marine biologist myself.

  If Darwin’s book on earthworms was a favorite of mine, so too was George John Romanes’s 1885 book, Jelly-Fish, Star-Fish, and Sea-Urchins: Being a Research on Primitive Nervous Systems, with its simple, fascinating experiments and beautiful illustrations. For Romanes, Darwin’s young friend and student, the seashore and its fauna were to be passionate and lifelong interests, and his aim above all was to investigate what he regarded as the behavioral manifestations of “mind” in these creatures.

  I was charmed by Romanes’s personal style. (His studies of invertebrate minds and nervous systems were most happily pursued, he wrote, in “a laboratory set up upon the sea-beach…a neat little wooden workshop thrown open to the sea-breezes.”) But it was clear that correlating the neural and the behavioral was at the heart of Romanes’s enterprise. He spoke of his work as “comparative psychology” and saw it as analogous to comparative anatomy.

  Louis Agassiz had shown, as early as 1850, that the jellyfish Bougainvillea had a substantial nervous system, and by 1883 Romanes demonstrated its individual nerve cells (there are about a thousand). By simple experiments—cutting certain nerves, making incisions in the bell, or looking at isolated slices of tissue—he showed that jellyfish employed both autonomous, local mechanisms (dependent on nerve “nets”) and centrally coordinated activities through the circular “brain” that ran along the margins of the bell.

  By 1884, Romanes was able to include drawings of individual nerve cells and clusters of nerve cells, or ganglia, in his book Mental Evolution in Animals. “Throughout the animal kingdom,” Romanes wrote,

  nerve tissue is invariably present in all species whose zoological position is not below that of the Hydrozoa. The lowest animals in which it has hitherto been detected are the Medusae, or jelly-fishes, and from them upwards its occurrence is, as I have said, invariable. Wherever it does occur its fundamental structure is very much the same, so that whether we meet with nerve-tissue in a jelly-fish, an oyster, an insect, a bird, or a man, we have no difficulty in recognizing its structural units as everywhere more or less similar.

  At the same time that Romanes was vivisecting jellyfish and starfish in his seaside laboratory, the young Sigmund Freud, already a passionate Darwinian, was working in the lab of Ernst Brücke, a physiologist in Vienna. His special concern was to compare the nerve cells of vertebrates and invertebrates, in particular those of a very primitive vertebrate (Petromyzon, a lamprey) with those of an invertebrate (a crayfish). While it was widely held at the time that the nerve elements in invertebrate nervous systems were radically different from those of vertebrate ones, Freud was able to show and illustrate, in meticulous, beautiful drawings, that the nerve cells in crayfish were basically similar to those of lampreys—or human beings.

  And he grasped, as no one had before, that the nerve cell body and its processes—dendrites and axons—constituted the basic building blocks and the signaling units of the nervous system. (Eric Kandel, in his book In Search of Memory, speculates that if Freud had stayed in basic research instead of going into medicine, perhaps he would be known today as “a co-founder of the neuron doctrine, instead of as the father of psychoanalysis.”)

  Although neurons may differ in shape and size, they are essentially the same from the most primitive animal life to the most advanced. It is their number and organization that differ: we have a hundred billion nerve cells, while a jellyfish has a thousand. But their status as cells capable of rapid and repetitive firing is essentially the same.

  The crucial role of synapses—the junctions between neurons where nerve impulses can be modulated, giving organisms flexibility and a whole range of behaviors—was clarified only at the close of the nineteenth century by the great Spanish anatomist Santiago Ramón y Cajal, who looked at the nervous systems of many vertebrates and invertebrates, and by Charles Sherrington in England (it was Sherrington who coined the word “synapse” and showed that synapses could be excitatory or inhibitory in function).

  In the 1880s, however, despite Agassiz’s and Romanes’s work, there was still a general feeling that jellyfish were little more than passively floating masses of tentacles ready to sting and ingest whatever came their way, little more than a sort of floating marine sundew.

  But jellyfish are hardly passive. They pulsate rhythmically, contracting every part of their bell simultaneously, and this requires a central pacemaker system that sets off each pulse. Jellyfish can change direction and depth, and many have a “fishing” behavior that involves turning upside down for a minute, spreading their tentacles like a net, and then righting themselves, which they do by virtue of eight gravity-sensing balance organs. (If these are removed, the jellyfish is disoriented and can no longer control its position in the water.) If bitten by a fish, or otherwise threatened, jellyfish have an escape strategy—a series of rapid, powerful pulsations of the bell—that shoots them out of harm’s way; special, oversize (and therefore rapidly responding) neurons are activated at such times.

  Of special interest and infamous reputation among divers are the box jellyfish (Cubomedusae)—one of the most primitive animals to have fully developed image-forming eyes, not so different from our own. The biologist Tim Flannery wrote of box jellyfish,

  They are active hunters of medium-sized fish and crustaceans, and can move at up to twenty-one feet per minute. They are also the only jellyfish with eyes that are quite sophisticated, containing retinas, corneas, and lenses. And they have brains, which are capable of learning, memory, and guiding complex behaviors.

  We and all higher animals are bilaterally symmetrical, having a front end (a head) containing a brain, and a preferred direction of movement (forwards). The jellyfish nervous system, like the animal itself, is radially symmetrical and may seem less sophisticated than a mammalian brain, but it has every right to be considered a brain, generating as it does complex adaptive behaviors and coordinating all the animal’s sensory and motor mechanisms. Whether we can speak of a “mind” here (as Darwin does in regard to earthworms) depends on how one defines “mind.”

  We all distinguish between plants and animals. We understand that plants,
in general, are immobile, rooted in the ground; they spread their green leaves to the heavens and feed on sunlight and soil. We understand that animals, in contrast, are mobile, moving from place to place, foraging or hunting for food; they have easily recognized behaviors of various sorts. Plants and animals have evolved along two profoundly different paths (fungi along yet another), and they are wholly different in their forms and modes of life.

  And yet, Darwin insisted, they were closer than one might think. He was reinforced in this notion by the demonstration that insect-eating plants made use of electrical currents to move, just as animals did—that there was “plant electricity” as well as “animal electricity.” But “plant electricity” moves slowly, roughly an inch a second, as one can see by watching the leaflets of the sensitive plant (Mimosa pudica) closing one by one along a leaf that is touched. “Animal electricity,” conducted by nerves, moves roughly a thousand times faster.*1

  Signaling between cells depends on electrochemical changes, the flow of electrically charged atoms in and out of cells via special, highly selective molecular pores or “channels.” These ion flows cause electrical currents, impulses—action potentials—that are transmitted (directly or indirectly) from one cell to another, in both plants and animals.

  Plants depend largely on calcium ion channels, which suit their relatively slow lives perfectly. As Daniel Chamovitz argues in his book What a Plant Knows, plants are capable of registering what we would call sights, sounds, tactile signals, and much more. Plants “know” what to do, and they “remember.” But without neurons, plants do not learn in the same way that animals do; instead they rely on a vast arsenal of different chemicals and what Darwin termed “devices.” The blueprints for these must all be encoded in the plant’s genome, and indeed plant genomes are often larger than our own.