God Soul Mind Brain

manner at the edges.

A ray gun to the soul

    Leave it to a scientist to do something monumentally stupid like shooting his own soul with a disruptor ray to prove a point. I am in the process of setting up an experiment that resembles a look-mom-no-hands moment. In a nutshell, I intend to map the parts of my own brain most responsible for perceiving other people’s awareness. I will do this by lying in an MRI scanner while performing tasks related to social perception. Once the relevant, active brain areas are pinpointed, I intend to disrupt them using an electromagnetic device. The device (called a Transcranial Magnetic Stimulator) passes a signal through the skull and disrupts the function of the brain tissue just under the bone. The disruption is generally accepted to be temporary—otherwise I wouldn’t do the experiment. (In my particular case, however, if I accidentally destroyed my circuitry for social intelligence probably nobody would notice the difference anyway.) Will I experience an awareness lapse? Will I fade back in and realize that I was gone for a moment? The experiment is about personal experience and self-report. It depends on testimonial rather than on any direct measurement. It is therefore probably not publishable in a scientific journal. But I still think the results will be interesting.

Chapter 8

    Mirror neurons

    When somebody near you smiles, you tend to smile. When somebody else yawns, you tend to yawn. When somebody leans back and crosses his hands behind his head, after a while three or four people around the room begin doing the same thing, largely unaware that they are imitating. Even when you do not overtly imitate someone else’s gesture, a part of your motor circuitry is probably rehearsing the act. Our motor systems mirror almost everything that we watch other people do. One of the most influential recent hypotheses about social perception is that we understand other people’s behavior by imitating it, though the imitation is usually a mental one and not an explicit, physical mimicry.

    This idea that people use imitation to understand each other was first proposed about fifty years ago by Liberman to explain how we understand speech. Human speech is fast and sometimes not enunciated very clearly. For example, the sounds of “b” and “d” are similar, yet to us they seem categorically different. How are we able to distinguish the sounds so effectively? Liberman proposed that we sub-vocally imitate. My neuronal machinery for speaking takes a try at a “b,” producing the right muscle output subtly and under my breath, and I decide whether the result matches the sound I heard. Everyone is aware of using this type of imitation from time to time in order to understand blurry speech. Liberman proposed that we do it unconsciously, all the time, and that it plays a fundamental role in our ability to correctly perceive speech sounds.

    This proposal, that we use imitation to understand each other, gained little traction for about thirty years. Then in the early 1990s, a new type of neuron was described in the motor cortex that seemed to confirm Liberman’s general idea.

    Rizzolatti and his colleagues in Italy were studying the monkey motor cortex, trying to understand the control of movement. They found a population of neurons that helped to control grasp. This region of motor cortex in the monkey brain is shown in Diagram 8-1 as the right-most shaded area.

    It is easy to understand how a neuron might control a muscle. When the neuron becomes active, it sends signals to a particular muscle, and that muscle contracts.

    It is also easy to understand how a neuron might control a dozen muscles. When that neuron becomes active, it sends signals to a dozen other neurons. Each of those in turn sends signals to a specific muscle.

    Diagram 8-1

    The grasp neurons described by Rizzolatti, however, seemed to operate at an even higher level of complexity. The grasp neurons were like generals sending commands to entire circuits of neurons, which in turn controlled muscles of the hand. When a grasp neuron became active, the monkey would reach out and pick something up. Different grasp neurons corresponded to different kinds of grasp. When one type of grasp neuron became active, the monkey might pick up a peanut carefully between forefinger and thumb in a precision grip. When a different type of grasp neuron became active, the monkey might pick up the peanut in a fist with all five