The Future of the Mind (7 page)

The temporal resolution of MRI machines is also limited because they
analyze the flow of oxygenated blood in the brain. The machine itself has very good temporal resolution, but tracing the flow of blood slows it down. In the future, other MRI machines will be able to locate different substances that are more directly connected to the firing of neurons, thereby allowing real-time analysis of mental processes. No matter how spectacular the successes of the past fifteen years, then, they were just a taste of the future.

NEW MODELS OF THE BRAIN

Historically, with each new scientific discovery, a new model of the brain has emerged. One of the earliest models of the brain was the “homunculus,” a little man who lived inside the brain and made all the decisions. This picture was not very helpful, since it did not explain what was happening in the brain of the homunculus. Perhaps there was a homunculus hiding inside the homunculus.

With the arrival of simple mechanical devices, another model of the brain was proposed: that of a machine, such as a clock, with mechanical wheels and gears. This analogy was useful for scientists and inventors like Leonardo da Vinci, who actually designed a mechanical man.

During the late 1800s, when steam power was carving out new empires, another analogy emerged, that of a steam engine, with flows of energy competing with one another. This hydraulic model, historians have conjectured, affected Sigmund Freud’s picture of the brain, in which there was a continual struggle between three forces: the ego (representing the self and rational thought), the id (representing repressed desires), and the superego (representing our conscience). In this model, if too much pressure built up because of a conflict among these three, there could be a regression or general breakdown of the entire system. This model was ingenious, but as even Freud himself admitted, it required detailed studies of the brain at the neuronal level, which would take another century.

Early in the last century, with the rise of the telephone, another analogy surfaced—that of a giant switchboard. The brain was a mesh of telephone lines connected into a vast network. Consciousness was a long row of telephone operators sitting in front of a large panel of switches, constantly plugging and unplugging wires. Unfortunately, this model said nothing about how these messages were wired together to form the brain.

With the rise of the transistor, yet another model became fashionable: the computer. The old-fashioned switching stations were replaced by microchips containing hundreds of millions of transistors. Perhaps the “mind” was just a software program running on “wetware” (i.e., brain tissue rather than transistors). This model is an enduring one, even today, but it has limitations. The transistor model cannot explain how the brain performs computations that would require a computer the size of New York City. Plus the brain has no programming, no Windows operating system or Pentium chip. (Also, a PC with a Pentium chip is extremely fast, but it has a bottleneck. All calculations must pass through this single processor. The brain is the opposite. The firing of each neuron is relatively slow, but it more than makes up for this by having 100 billion neurons processing data simultaneously. Therefore a slow parallel processor can trump a very fast single processor.)

The most recent analogy is that of the Internet, which lashes together billions of computers. Consciousness, in this picture, is an “emergent” phenomenon, miraculously arising out of the collective action of billions of neurons. (The problem with this picture is that it says absolutely nothing about how this miracle occurs. It brushes all the complexity of the brain under the rug of chaos theory.)

No doubt each of these analogies has kernels of truth, but none of them truly captures the complexity of the brain. However, one analogy for the brain that I have found useful (albeit still imperfect) is that of a large corporation. In this analogy, there is a huge bureaucracy and lines of authority, with vast flows of information channeled between different offices. But the important information eventually winds up at the command center with the CEO. There the final decisions are made.

If this analogy of the brain to a large corporation is valid, then it should be able to explain certain peculiar features of the brain:

•  
Most information is “subconscious”
—that is, the CEO is blissfully unaware of the vast, complex information that is constantly flowing inside the bureaucracy. In fact, only a tiny amount of information finally reaches the desk of the CEO, who can be compared to the prefrontal cortex. The CEO just has to know information important enough to get his attention; otherwise, he would be paralyzed by an avalanche of extraneous information.
   
This arrangement is probably a by-product of evolution, since our ancestors would have been overwhelmed with superfluous, subconscious information flooding their brains when facing an emergency. We are all mercifully unaware of the trillions of calculations being processed in our brains. Upon encountering a tiger in the forest, one does not have to be bothered with the status of our stomach, toes, hair, etc. All one has to know is how to run.

•  
“Emotions” are rapid decisions made independently at a lower level
. Since rational thought takes many seconds, this means that it is often impossible to make a reasoned response to an emergency; hence lower-level brain regions must rapidly assess the situation and make a decision, an emotion, without permission from the top.
   So emotions (fear, anger, horror, etc.) are instantaneous red flags made at a lower level, generated by evolution, to warn the command center of possibly dangerous or serious situations. We have little conscious control over emotions. For example, no matter how much we practice giving a speech to a large audience, we still feel nervous.
   Rita Carter, author of
Mapping the Mind
, writes, “
Emotions are not feelings at all but a set of body-rooted survival mechanisms that have evolved to turn us away from danger and propel us forward to things that may be of benefit.”

•  
There is a constant clamoring for the attention of the CEO
. There is no single homunculus, CPU, or Pentium chip making decisions; instead, the various subcenters within the command center are in constant competition with one another, vying for the attention of the CEO. So there is no smooth, steady continuity of thought, but the cacophony of different feedback loops competing with one another. The concept of “I,” as a single, unified whole making all decisions continuously, is an illusion created by our own subconscious minds.
   Mentally we feel that our mind is a single entity, continuously and smoothly processing information, totally in charge of our decisions. But the picture emerging from brain scans is quite different from the perception we have of our own mind.
   MIT professor Marvin Minsky, one of the founding fathers of artificial intelligence, told me that
the mind is more like a “society of minds,” with different submodules, each trying to compete with the others.
   
When I interviewed Steven Pinker, a psychologist at Harvard University, I asked him how consciousness emerges out of this mess. He said that
consciousness was like a storm raging in our brain. He elaborated on this when he wrote that “
the intuitive feeling we have that there’s an executive ‘I’ that sits in a control room of our brain, scanning the screens of the senses and pushing the buttons of our muscles, is an illusion.
Consciousness turns out to consist of a maelstrom of events distributed across the brain. These events compete for attention, and as one process outshouts the others, the brain rationalizes the outcome after the fact and concocts the impression that a single self was in charge all along.”

•  
Final decisions are made by the CEO in the command center
. Almost all the bureaucracy is devoted to accumulating and assembling information for the CEO, who meets only with the directors of each division. The CEO tries to mediate all the conflicting information pouring into the command center. The buck stops here. The CEO, located in the prefrontal cortex, has to make the final decision. While most decisions are made by instinct in animals, humans make higher-level decisions after sifting through different bodies of information from our senses.

•  
Information flows are hierarchical
. Because of the vast amount of information that must flow upward toward the CEO’s office, or downward to the support staff, information must be arranged in complex arrays of nested networks, with many branches. Think of a pine tree, with the command center on top and a pyramid of branches flowing downward, branching out into many subcenters.
   There are, of course, differences between a bureaucracy and the structure of thought. The first rule of any bureaucracy is that “it expands to fill the space allotted to it.” But wasting energy is a luxury the brain cannot afford. The brain consumes only about twenty watts of power (the power of a dim lightbulb), but that is probably the maximum energy it can consume before the body becomes dysfunctional. If it generates more heat, it will cause tissue damage. Therefore the brain is constantly using shortcuts to conserve energy. We will see throughout this book the clever and ingenious devices that evolution has crafted, without our knowledge, to cut corners.

IS “REALITY” REALLY REAL?

Everyone knows the expression “seeing is believing.” Yet much of what we see is actually an illusion. For example, when we see a typical landscape, it seems like a smooth, movielike panorama. In reality, there is a gaping hole in our field of vision, corresponding to the location of the optic nerve in the retina. We should see this large ugly black spot wherever we look. But our brains fill in that hole by papering it over, by averaging it out. This means that part of our vision is actually fake, generated by our subconscious minds to deceive us.

Also, we see only the center of our field of vision, called the fovea, with clarity. The peripheral part is blurry, in order to save energy. But the fovea is very small. To capture as much information as possible with the tiny fovea, the eye darts around constantly. This rapid, jiggling motion of our eyes is called saccades. All this is done subconsciously, giving us the false impression that our field of vision is clear and focused.

When I was a child and first saw a diagram showing the electromagnetic spectrum in its true glory, I was shocked. I had been totally unaware that huge parts of the EM spectrum (e.g., infrared light, UV light, X-rays, gamma rays) were totally invisible to us. I began to realize that what I saw with my eyes was only a tiny, crude approximation of reality. (There is an old saying: “If appearance and essence were the same thing, there would be no need for science.”) We have sensors in the retina that can detect only red, green, and blue. This means that we’ve never actually seen yellow, brown, orange, and a host of other colors. These colors do exist, but our brain can approximate each of them only by mixing different amounts of red, green, and blue. (You can see this if you look at an old color-TV screen very carefully. You see only a collection of red, green, and blue dots. Color TV is actually an illusion.)

Our eyes also fool us into thinking we can see depth. The retinas of our eyes are two-dimensional, but because we have two eyes separated by a few inches, the left and right brain merge these two images, giving us the false sense of a third dimension. For more distant objects, we can judge how far an object is by observing how they move when we move our head. This is called parallax.

(This parallax explains the fact that children sometimes complain that “the moon is following me.” Because the brain has difficulty comprehending the parallax of an object as distant as the moon, it appears as if the moon is
always a fixed distance “behind” them, but it’s just an illusion caused by the brain taking a shortcut.)

THE SPLIT-BRAIN PARADOX

One way in which this picture, based on the corporate hierarchy of a company, deviates from the actual structure of the brain can be seen in the curious case of split-brain patients. One unusual feature of the brain is that it has two nearly identical halves, or hemispheres, the left and right. Scientists have long wondered why the brain has this unnecessary redundancy, since the brain can operate even if one entire hemisphere is completely removed. No normal corporate hierarchy has this strange feature. Furthermore, if each hemisphere has consciousness, does this mean that we have two separate centers of consciousness inside one skull?

Dr. Roger W. Sperry of the California Institute of Technology won the Nobel Prize in 1981 for showing that the two hemispheres of the brain are not exact carbon copies of each other, but actually perform different duties. This result created a sensation in neurology (and also spawned a cottage industry of dubious self-help books that claim to apply the left-brain, right-brain dichotomy to your life).

Dr. Sperry was treating epileptics, who sometimes suffer from grand mal seizures often caused by feedback loops between the two hemispheres that go out of control. Like a microphone screeching in our ears because of a feedback loop, these seizures can become life-threatening. Dr. Sperry began by severing the corpus callosum, which connects the two hemispheres of the brain, so that they no longer communicated and shared information between the left and right side of the body. This usually stopped the feedback loop and the seizures.

At first, these split-brain patients seemed perfectly normal. They were alert and could carry on a natural conversation as if nothing had happened. But a careful analysis of these individuals showed that something was very different about them.

Normally the hemispheres complement each other as thoughts move back and forth between the two. The left brain is more analytical and logical. It is where verbal skills are found, while the right brain is more holistic and artistic. But the left brain is the dominant one and makes the final decisions. Commands pass from the left brain to the right brain via the corpus callosum.
But if that connection is cut, it means that the right brain is now free from the dictatorship of the left brain. Perhaps the right brain can have a will of its own, contradicting the wishes of the dominant left brain.