The Brain: Our Universe Within
TV Series Host: David Suzuki
Review Essay by Sally Morem
In 1998, Discovery Channel presented The Brain: Our Universe Within, a good basic introduction to some of the latest discoveries in neuroscience. It featured real life stories of people suffering from various brain diseases. It also featured terrific computer graphics of neurons, synapses, and neural pathways, which clarified some difficult scientific concepts for the viewer. Dr. David Suzuki hosted the series just as he had for the critically acclaimed PBS series, The Secret of Life, in 1993.
Paleontologists uncovered remains of Neanderthals in the Shanidar Caves in the Middle East. Here was early evidence that ancient humans mourned their dead. Skeletons were found with wildflower pollen covering them. The mourners had dropped flowers on the body of the loved one during burial ceremonies. One elderly man had been physically disabled for years before he died. Clearly, his people cared for him when he couldn't care for himself. All of this is evidence of the existence of ancient human community and the ability of people to engage in highly abstract thought long before any of the ancient Middle Eastern civilizations came to be.
Evolving consciousness in humans corresponds to the evolving physical brain. Evolutionary processes over hundreds of millions of years added new parts of the brain to the old, creating new capabilities and new species. This process began with primitive sea creatures. They possessed a simple neural tube connecting organs to a primitive processor of sensation and response. This neural tube much later evolved into a tiny brain, very similar in form and function to the human brain stem. Eventually, this tiny brain became very big indeed as it developed 100 billion neurons with up to 50,000 different connections per brain cell, creating trillions of neural networks, which created detailed internal representations of the outer world, which permitted ideas, thoughts, and finally, a sense of Self to grow. This brain is also known as the human brain.
Neurons are overproduced in the fetal brain. Half of them die off when the child is very young. As neurons `compete' to handle specific sensory inputs, the child's brain continues to develop physically well into the teenage years. This dynamic system of ever-changing synaptic networks continually shapes and reshapes itself. The environment actually changes the physical brain, creating “neural maps” to handle sights, sounds, language, and perception. As it does so, neurons grow new connections to handle these specific inputs and prune neural circuits that aren't used. This combination of growth and pruning creates human individuality. No two brains, not even those of identical twins, are the same. Since we all experience the world in different ways, our brains develop differently in response to the differing stimuli. We are not predestined by our DNA. Our genes permit the growth of neurons, but they don't specify the exact interconnections between each cell.
An MRI scan shows the brain in action. Brain activity levels are indicated by false colors—white for the most activity, warm colors for a lot of activity, cool colors for less, and finally black for no brain activity. We can see color changes in parts of the brain in response to finger movements or a change in scenery. By studying the activity of the brain in this way, neuroscientists have mapped the specialized parts of the brain.
How does the brain work? A combination of electrical and chemical signals sends messages from neuron to neuron in a fantastically complex dance of neural activity. Chemicals called neurotransmitters mediate the quantity and quality of transmissions. Billions of such signals allow the brain to build mental constructs of the outer world.
Our conscious selves do not apprehend the world directly. The brain filters the avalanche of sense data so that the conscious mind need not be overwhelmed by minutiae. Each of us sees the world differently. Thanks to the differences in how our brains are wired, we create subtly, and sometimes radically, differing mental constructs of our environment. Our brain deconstructs then reconstructs impressions of the outside world.
When the brain doesn't work the way it should, filtering the unending barrage of sensation from the conscious mind, the mind suffers from the onslaught. This is what happens to autistic people. Sensory overload overwhelms thought processes. Autistic people withdraw because everything seems much too much. They fear touch because the touch sensation is so strong. They prize regularity in their surroundings because this means less threatening additional change that must be processed by the deluged brain.
Information on the visual world is gathered by the eyes from light patterns and is processed successively by many strata of neurons in the visual cortex. Images are flipped, split up and segmented by these processors, and parceled out to various brain centers for further processing. The cerebral cortex receives the processed information, allowing the conscious mind to finally “see” the image.
The principle of the division of labor is fully utilized by the brain. Columns of neurons that analyze aspects of an image—the direction of lines, the size and orientation of shapes, the brightness and hue of colors—then communicate with one another, rebuilding the image as an internal mental construct.
Damage to any part of the visual cortex can cause strange effects. One woman couldn't see motion. Changes in the world around her manifested themselves in her mind in “freeze frames.” A man couldn't recognize his own photograph taken several years earlier.
Tactile sensations are sent to a thin strip of neurons that act as a tactile map of the body. Sound is received by the ears and transformed progressively into signals to the auditory cortex. Some neurons specialize in the analysis of pitch, tempo and loudness. A blind, mentally retarded man could replay any song after one hearing. Apparently neurons were compensating for what was lacking in the damaged part of the brain.
The sense of smell is our first evolutionary sense, and in many respects the most basic sense. Often, specific scents and odors bring back very specific memories. Babies react to the precise smells given off by their mother's breast. Olfactory neurons translate smells into neural transmissions, which spread in waves throughout the brain. There are special links that communicate directly to the limbic system, the seat of our emotions. Smell augments the simple taste sensations—salt, sour, bitter and sweet—picked up by taste buds on the tongue. Food preferences can be remembered for a lifetime as tastes are stored by the brain.
Francis Crick, co-discoverer of the double helix of DNA, is now studying the workings of the visual cortex, the place in the brain where visual inputs are broken apart, analyzed and put back together again. He discovered that a series of neurons fire simultaneously while the subject was looking at something. This simultaneity may explain a crucial aspect of consciousness—many parts of the brain dealing with aspects of a thing being considered at the same time. Various groups of neurons—brain centers, if you will—interact with one another in such a way as to create “more than the sum of their parts.” I suspect this means that when enough subsystems of the brain are thus engaged, the visceral sense of Self we all experience is triggered.
Where does all this information get assembled? There may be no one particular place, no central processing unit in the brain. Our coherent view of the world may come together throughout the brain, linked by pulsing neurons times to synchronize together. So, we see the specialized centers of the brain constantly sending, receiving, and processing information about the internal state of the body and the external state of the environment, while the cerebral cortex “thinks” about it all. A continually self-organized, self-correcting “information superhighway” reflecting upon the world.
One of the most crucial aspects of the brain, which gives us a continual sense of Self, is memory. Scientists have tracked the activity of the brain as subjects engage in memory tests. Information gathered by the senses is gathered and stored in the temporal lobe, specifically in the hippocampus. If the hippocampus or the pathway to it is blocked or destroyed, the mind can no longer lay down new memories. Short-term memory is gone. One man with short-term memory loss must keep extensive notes so that he may keep track of his life minute by minute. His long-term memory is still there, allowing him to retain a sense of Self, but the sense of time passing, learning, and growing is gone.
Long-term memory—repeated signals that strengthen neural connections—is built up over several hours to several weeks. Permanent storage is accomplished when the hippocampus finishes processing the memory and sends it to the neocortex. Memories are broken down into pieces and stored in various parts of the cortex, interlinked with related pieces of other memories. The triggering of one memory can set off a chain reaction of memories. These memories can be thought of as “chains with many links” or “idea networks.”
Memories of skills can be retained by amnesiacs because these are laid down in the brain differently than ordinary memories. In fact, the man with short-term memory loss can learn a skill and keep it, yet not remember how he learned it.
Alzheimer's Disease does more than destroy memory; eventually it destroys all brain functions as the brain is riddled with more and more tangles of diseased neurons in a cheesy mess of proteins. These shred vital interconnections that allow the mind to work and makes it human. Normally, when we lose brain cells, others can take up their work. Rich connections are continually being made. When we develop our mind and maintain a high level of mental activity, we may be able to avoid Alzheimer's altogether or at least mitigate its effects. Other parts of the brain can take over the functions of damaged parts.
Advanced Alzheimer's patients suffer from the virtual destruction of their personalities. PET scans reveal very little brain activity in these patients as compared to activity in a healthy brain. A substance called beta aneloid seems to speed up the disease process. Four faulty genes may be involved in the excess production of this substance, allowing it to build up in neural pathways.
Strokes are also severely disruptive of brain processes. One woman suffered a stroke and was near death. Her right side was paralyzed because the left side of the brain was cut off from vital blood supplies carrying oxygen to the neurons. Her neurons died in massive numbers. We see a computer graphic revealing the destruction. The left hemisphere of the brain is virtually empty of activity. But even after the damage, other neurons in the right hemisphere were able to take over the work of those destroyed.
Stroke victims can recover more functions faster if their brains receive a lot of stimuli. Children especially have strong recuperative powers. One child, born with most of his brain nonfunctional, can walk, see, and hear because that part of his brain, which is still working, took over most of the functions of the whole brain. The child's brain, with young neurons, is much more elastic than an adult's brain. Young neurons reconnect with others very rapidly.
A boy with severe epilepsy had the left half of his brain removed to stop the seizures. A few years later, most of the right side of his body is no longer paralyzed. He can now speak, even thought the speech center is normally on the left side of the brain. His speech center has migrated to the right side of his brain.
How does the brain rehabilitate itself? We watch through an electron microscope as two young neurons establish a connection. We watch again as macrophages `eat' damaged nerves and clear them away, leaving room for healthy neurons to grow new fibers to take up the work of the dead neurons.
The left and right hemispheres of the brain work together to produce meaning. The right brain handles emotions while the left brain produces intelligibility. Without the right, we can only produce a cold recitation of the facts. Without the left, we can only express highly emotional grunts and squeals.
The brain stem controls basic bodily functions. But one small part is connected with many parts of the rest of the brain. This part of the brain stem signals the rest of the brain to stimulate production of noradrenalin, an anti-depressant. The biological equivalent of willpower.
What do hallucinogens do to the brain and consciousness? The brain is a chemical factory, turning out a hodgepodge of neurotransmitters. These trigger electric impulses from neuron to neuron. There are special receptors for neurotransmitters at the end of the synapses. Neurotransmitters modify human behavior, convey emotions, control moods, increase or decrease appetite, and reinforce or undercut learning.
Hallucinogens interfere with this activity, especially in the hypothalamus where all sensory information is funneled before entering the neocortex. Psychoactive drugs are similar in structure to serotonin and can bond with serotonin receptors, triggering information overload and creating hallucinations.
Exercise, fasting, and even deep breathing can affect the brain in similar ways. A group of Japanese pilgrims fast and chant sutras high in the wintery mountains. They engage in solitary meditations for hours at a time. On the third day of their pilgrimage, they begin to experience vivid hallucinations. The hallucinations grow in intensity thereafter. Blood samples were taken during the pilgrimage. Doctors discovered that the pilgrims' bodies were producing serotonin in prodigious amounts.
Dopamine is an inhibitory neurotransmitter. It dampens the brain's signals. It helps the basil ganglia to produce smooth, controlled movements. Damage to the basil ganglia or lack of dopamine can cause Parkinson's disease, the major symptoms of which are jerky, uncontrolled movements.
Schizophrenia may result from a lack of dopamine, also. Schizophrenia consists of shattered, uncontrolled thoughts. Brains of patients reveal decreased blood flow in the frontal lobes, the seat of reasoning. Dopamine also produces feelings of bliss and regulates the perception of pain.
Dopamine and other endorphins mediate pain. They enter the opiate receptors at the ends of the synapse. Extra endorphins can be triggered by grueling physical activity, producing “runner's high.” Dopamine also produces sexual arousal and feelings of love. A surge of dopamine gives us feelings of wellbeing. The limbic system takes over and sweeps us away with infatuation. One endorphin, oxytocin, has been called the “cuddle” chemical. It gives mothers the urge to hold and nurse their infants.
Does all this hard-edged scientific study of human emotions and neural processes rob them of their value and importance—of their authenticity? Are we engaging in reductionism? Do we reduce our emotions, our thoughts, even ourselves to biochemical reactions? Will this diminish our sense of Self? We are not merely our neurons and neurotransmitters. Remember that the brain is an exceedingly complex system of messages and chemistry. We are more than the sum of our parts. We are synergistically elf-organizing entities composed of thousands of levels of chemical, biological, and neural organization, each level building upon the organized patterns of matter and energy that those below it have established, and creating new and more comprehensive and flexible levels of organization above themselves.
As we've seen, each one of us possesses a unique set of neural networks. Our individuality, our very Self, is rooted in this vast interplay of incomprehensibly complex electrochemical interactions. As such, each of us, just as the ancient peoples of the Shanidar Caves, is irreducible to our constituent parts and irreplaceable in the broader scheme of things.