From Angels to Neurons

Dreaming—so like waking consciousness as to fool us almost every time, and yet so different as to amaze us upon awakening—has long fascinated both artists and scientists who have worked to describe and explain it. In their efforts to understand the connection between dreams and the brain-mind, scientists as well as artists use visual images to convey directly and concisely their insights into dreaming. This essay presents a series of images from their dialogue across the centuries about dreaming.

Here Rene Magritte captures the essence of the bizarre nature of dreams with this toy locomotive chugging out of an ordinary living room fireplace. Both the train and the mantelpiece are realistic, but their juxtaposition is as disturbingly incongruous as the strange conjunctions of people, places, and actions in our dreams. In emphasizing dreaming’s formal properties, rather than attempting to interpret its symbolic content, modern artists and scientists have finally developed a common path of inquiry. By formal properties, I mean, for example, the hallucinatory imagery, the delusional belief that we are awake, the bizarre cognition, and the amnesia that characterize all dreams.

Time Transfixed
RENE MAGRITTE, 1938

Understanding the Stuff that Dreams Are Made of

The Head of Hypnos
GREEK, LATE 4TH CENTURY BC

In Greek Mythology, Hypnos, the God of Sleep, was the son of Nyx (Night) and the brother of Thanatos (Death). He resided in a dark, misty cave with his three sons: Morpheus, who brought dreams to men; Icelus, who brought dreams to animals; and Phantasus, who brought dreams to inanimate objects. These were all winged gods whose lightness and speed could explain their ubiquity and evanescence. The Romans borrowed the concept of winged gods to explain not only sleep and dreams, but also love. In the Classical period, it was typical to attribute states of consciousness such as these to spirits from other worlds.

Sleeping Man and Cat
PHOTO: TED SPAGNA / DRAWING: J. ALLAN HOBSON

Modern sleep research is materialistic. It uses human subjects whose brain, eye, and muscle activities can be recorded in sleep laboratories using electronic measuring machines called polygraphs. At different stages of sleep, the subjects are awakened and asked about mental activity such as dreams. Sleep researchers also study animals such as the cat, whose neurophysiology can be described at the level of single cells and molecules.

We now know that the brain is activated periodically during sleep. When we dream, the brain’s electrical activity is exactly the same as when we are awake, but most sensory input and motor output are blocked. Periods of REM (rapid eye movement) sleep are associated with dreams in which vivid perceptions arise spontaneously and are knit together into a coherent story. The fleeting quality of our dreams comes not from the lightness and whimsical nature of winged messengers but from the alterations of our brain physiology and chemistry in REM sleep.

Angels or Eye Movements

Genesis: Abraham and Isaac; Jacob’s Ladder
LAMBETH BIBLE, CANTERBURY, ENGLAND (c.1140-50)

Christianity translated the pagan winged god into its own external agent, the angel, who mediated between the realm of God and the realm of man and brought messages to enlightened dreamers. Thus the dream itself was seen as an intermediary between matter and spirit. Even later thinkers who, like the French philosopher René Descartes (15961650), understood the reality of the physical brain could not imagine its relationship to our mental experience. Modern Rationalist thought carried forward this idea of separateness of mind and body, both of which were synchronously moved by an external agency: the “angel of angels,” God.

Human NREM-REM Cycle
UNPUBLISHED DATA FROM FREDERICK SNYDER AND J. ALLAN HOBSON

Scientists now interpret our mental experience of dreaming as inseparable from the physical activity of our brains. Each night, the periodic occurrence of REM sleep (solid bars) is interspersed with a four-stage process of brain deactivation called NREM sleep, when the brain’s electrical activity, as measured with EEG, is disorganized. During NREM sleep we are deeply unconscious, especially early in the night when awakenings are difficult and we may become confused when awakened. As the night progresses, the REM periods get longer and the NREM periods get shorter and more shallow, so that by morning the distinctions between them are almost lost. But the periods are fixed at 90-100 minutes and the amount of REM is constant at 20-30% of each night. That means we dream an average of two hours per night—50,000 hours or 6 years over a lifespan of 70 years.

The Physical Reality of Sleep

Venus and Mars
SANDRO BOTTICELLI (1444-1510)

By the height of the Renaissance, the Christian angels disappeared and a frank interest in the human body and the physical reality of sleep gained the upper hand. Botticelli, using the pagan gods Venus and Mars as an allegorical vehicle, anticipated our modern scientific interest in the direct observation of sleep. At the time of Leonardo da Vinci, who drew the skull and its mysterious content, the brain, feeling states, and consciousness itself began to be ascribed to the fluid-filled cavities (ventricles) and parts of the brain.

Pontine Brain Stem REM-on Cell with Eye Movement
J. ALLAN HOBSON

We can now look far deeper into the brain than da Vinci’s controversial dissections of human cadavers. By introducing microscopic electrodes into the brain stem of an animal, we can record from individual neurons and obtain an indication of their electrical signals (red trace) in REM sleep. This neuron fires a cluster of 13 electrical signals (called action potentials) just before the eye begins to move (blue trace), suggesting that this particular cell might actually command the movement or REM sleep. By studying thousands of cells, scientists have been able to account for many of the physiological aspects of REM sleep, such as internal visual stimulation, in terms of specific cells and molecules.

Cosmic Clockwork

The Music of the Spheres
15TH CENTURY ETCHING, ARTIST UNKNOWN

With the rise of invention and exploration in the fifteenth century, models of the universe became increasingly mechanical. Clockwork is an obvious inspiration for this image, in which the late medieval pilgrim has reached the edge of the physical universe and—insatiably curious—has pushed his head through this barrier to listen to the music of the celestial spheres. Now we  are learning to look at the cosmos inside the human head and to discern the clockwork within the brain so that we may understand the orchestration of our states of consciousness. The heavenly spheres of today are nerve cells and their music is the electrical activity that is the physical basis of our minds.

REM-on Cell in Pons
NISSL STAIN, J. ALLAN HOBSON

Using aniline dyes, it is possible to stain the large bodies of giant cells in the part of the brain stem called the pons that fire intensely during REM sleep and probably drive the eye movements that accompany it. These stains allow us to visualize the cell’s nucleus, although not the dendrites and axons by which the cell receives and sends information. Cells such as these control the inhibition of muscles and still others control the activation of the brain. When cells are excited by the brain’s chemical messenger, acetylcholine, a REM sleep episode and dreaming are triggered.  Cells that contain the chemical norepinephrine—and are thought to be important for attention, learning, and memory during waking—fall silent during REM sleep. Their inactivity may result in the increased excitability of the REM-on cells and some of the peculiarities of dreams, such as bizarreness, illogical thinking, and inablity to recall most dreams.

Inspired Dreaming

The Dream of the Palace
GIOTTO DI BONDONE (1266-1336), (SCHOOL OF), ASSISI

Medieval angelic emissaries were seen as conveying the commands of God to his human servants in dreams; here, an angel shows the sleeping St. Francis an elaborate architectural plan for building a church.

Artists and scientists still achieve insights through inventive and creative dreaming, such as Otto Loewi’s dream of the crossed frog heart perfusion experiment, which demonstrated that a chemical from the heart nerves of one animal could influence the heart action of another. The chemical that caused the recipient frog’s heart to slow when Loewi stimulated the vagus nerve of the donor turned out to be acetylcholine, the same neurotransmitter that the brain uses to generate REM sleep.

Dream Bicycle
DREAM JOURNAL OF THE ENGINE MAN, OCTOBER 10-11, 1939

Since acetylcholine can induce REM sleep and dreaming, it was responsible in a sense for Loewi’s Nobel Prize winning insight, as well as this playful dream invention. The “artist” in this case was a Smithsonian insect specialist  who took it upon himself to record—and illustrate—all of his dreams in the summer of 1939. His bicycle built for two is driven by his bachelor self, but there is a seat available for a companion. Bizarre images in dreams may be meaningful even if they are incongruous.

Riding the Night Mare

The Nightmare
HENRY FUSELI, 1782

Troubled sleep interested Henry Fuseli (1742-1825), who painted at least 40 variations of this nightmare scene. His friend William Blake and the poet Samuel Coleridge both actively manipulated their sleep and dreams to achieve artistic and poetic inspiration. For Fuseli, the nightmare was the joint responsibility of a wild horse and a demon—or incubus—who sat on the sleeper’s chest, causing the sense of pressure and pounding heart. It was clear to the Romantics that the sleeping mind was subject to unpleasant disruptions that could put them in touch with their creative selves. We now know that the horse and the incubus are symbols of the periodic internal activation of the brain and the cardiorespiratory systems while we sleep.

Autonomic Storms in Sleep
J. ALLAN HOBSON

During REM sleep (shown here), or on arousal from nonREM sleep, rapid heart beats, heavy or arrested breathing, and dramatic rises and falls in blood pressure often produce intense anxiety. The sleeper may experience terror in association with these autonomic storms, which are generated by the amygdala and other emotional centers of the brain.

A Flash of Dreaming Consciousness

Le Reve
ODILON REDON, 1904

Raised in the dark shadows of his Bordeaux family manse, the French symbolist painter Odilon Redon worked entirely in black and white until he was almost 60, when radiant color broke through—as in a flash of heightened consciousness in a dream. Throughout his career, Redon treated dreaming as a germinal and primordial mental process. In this late painting, the red hot spot of activation gives way to a smoke screen of synthetic imagining. The sense of an internal illumination source for the dream is clearly expressed, although Redon did not know that the hot spot was the pontine brain stem and the cerebral cortex was the screen of his imagination.

REM Sleep PET Scan
PIERRE MAQUET

Imaging is a direct method of visualizing activity in the brain during REM sleep by means of techniques that measure changes in the flow of blood as neurons are activated. Through PET scans, we can see the activation of the pontine brain stem (perhaps the trigger zone for our dreams, as it is in animals), the areas of the cortex for visual perception and spatial integration (perhaps the seat of hallucinatory imagery), and the amygdala (perhaps the seat of dream anxiety). Equally important may be the deactivation of the dorsolateral prefrontal cortex, which is thought to be the seat of working memory and other executive functions that are quiescent in dreaming.

Understanding the Mystery

L’Ecole des Savants
PAUL DELVAUX, 1958

A dream with a surreal combination of railroad trains, street lights, and eerily open spaces is represented in the center of this painting. Delvaux suggest that it could be studied in two ways. On the right, psychoanalysts scrutinize a live patient and attribute the dream images to a symbolic disguise of unconscious impulses—mostly sexual. On the left, neurologists examine a cadaver’s brain looking for hints about the mechanics of producing dream images. Delvaux does not appear optimistic about either approach, preferring to celebrate rather than to solve the central mystery. But now we can study both the brain and the mind in living conjunction and map the form of dreams onto the form of brain activity in REM sleep. We now see dreaming as the brain’s complex awareness of its autoactivated state in sleep. Our understanding of dreaming has changed dramatically from the concepts of pagan gods and Christian angels, but our modern vision is no less elaborate and no less beautiful.