morality, traits that are especially well developed in humans. Unless you are a sociopath (who has disturbances in these circuits, as shown by Antonio Damasio), you don’t usually lie or cheat, even when 100 percent sure you could get away with it if you tried. Indeed, your sense of morality and your concern for what others think of you are so powerful that you even act to extend them beyond your death. Imagine you have been diagnosed with terminal cancer and have old letters in your drawers that could be dredged up after your death, incriminating you in a sex scandal. If you are like most people, you will promptly destroy the evidence, even though logically, why should your posthumous reputation matter to you once you are gone?
I have already hinted at the role of mirror neurons in empathy. Apes almost certainly have empathy of sorts, but humans have both empathy and “free will,” the two necessary ingredients for moral choice. This trait requires a more sophisticated deployment of mirror neurons—acting in conjunction with the anterior cingulate—than any ape before us has achieved.
Let’s turn now to the dorsomedial prefrontal area (DMF). The DMF has been found in brain-imaging studies to be involved in conceptual aspects of the self. If you are asked to describe your own attributes and personality traits (rather than someone else’s), this area lights up in brain-imaging studies. On the other hand, if you were to describe the raw feel of your embodiment, one would expect your VMF to light up, but this hasn’t been tested yet.
Lastly, there is the dorsolateral prefrontal area. The DLF is required for holding things in your current, ongoing mental landscape, so you can use your ACC to direct attention to different aspects of the information and act according to your desires. (The technical name for this function is working memory.) The DLF is also required for logical reasoning, which involves paying attention to different facets of a problem and juggling abstractions—such as words and numbers—synthesized in the inferior parietal lobules (see Chapter 4). How and where the precise rules for this juggling arise is anybody’s guess.
The DLF also interacts with the parietal lobe. The two act jointly to construct a consciously experienced, animated body moving in space and time (which complements the insula-VMF pathway’s creation of a more viscerally felt anchoring of your self in your body). The subjective boundary between these two types of body image is somewhat blurred, reminding us of the sheer complexity of connections needed for even something as “simple” as your body image. This point will be driven home later; we will encounter a patient with a phantom twin next to him. Vestibular stimulation caused the twin to shrink and move. This implies powerful interactions between (a) vestibular input to the insula, which produces a visceral anchoring of the body, and (b) vestibular input to the right parietal lobe, which—along with muscle, joint sense, and vision—constructs a vivid sense of a consciously experienced, moving body.
Unity
What if the self is produced not by a single entity but by the push and pull of multiple forces of which we are largely unconscious? Now I’ll use the lenses of anosognosia and out-of-body experiences to examine the unity—and disunity—of the self.
HEMISPHERIC SPECIALIZATION: DOCTOR, I AM IN TWO MINDS
A great deal of pop psychology deals with the question of how the two hemispheres might be specialized for different roles. For example, the right hemisphere is thought to be more intuitive, creative, and emotional than the left, which is said to be more linear, rational, and Spock-like in its mentality. Many a New Age guru has used the idea to promote ways of unleashing the hidden potential of the right hemisphere.
As with most pop ideas, there is a kernel of truth to all this. In
Information arriving through the senses is ordinarily merged with preexisting memories to create a belief system about yourself and the world. This internally consistent belief system, I suggest, is constructed mainly by the left hemisphere. If there is a small piece of anomalous information that doesn’t fit your “big picture” belief system, the left hemisphere tries to smooth over the discrepancies and anomalies in order to preserve the coherence of self and the stability of behavior. In a process called confabulation, the left hemisphere sometimes even fabricates information to preserve its harmony and overall view of itself. A Freudian might say that the left hemisphere does this to avoid shattering the ego, or to reduce what psychologists refer to as cognitive dissonance, a disharmony between different internal aspects of self. Such disconnects give rise to the confabulations, denials, and delusions that one sees in psychiatry. In other words, Freudian defenses originate mainly in the left hemisphere. In my account, however, unlike in orthodox Freudianism, they evolved not to “protect the ego” but to stabilize behavior and impose a sense of coherence and narrative to your life.
But there has to be a limit. If left unchecked, the left hemisphere would likely render a person delusional or manic. It is one thing to play down some of your weaknesses to yourself (an unrealistic “optimism” may be useful temporarily for forging ahead), but another thing to delude yourself into thinking you are rich enough to buy a Ferrari (or that your arm is not paralyzed) when neither is true. So it seems reasonable to postulate a “devil’s advocate” in the right hemisphere that allows “you” to adopt a detached, objective (allocentric) view of yourself.9 This right-brain system would often be able to detect major discrepancies that your egocentric left hemisphere has ignored or suppressed but shouldn’t have. You are then alerted to this, and the left hemisphere is jolted into revising its narrative.
The notion that many aspects of the human psyche might arise from a push-pull antagonism between complementary regions of the two hemispheres might seem like a gross oversimplification; indeed, the theory itself might be the result of “dichotomania,” the brain’s tendency to simplify the world by dividing things into polarized opposites (night and day, yin and yang, male and female, and so on). But it makes perfect sense from a systems engineering point of view. Control mechanisms that stabilize a system and help avoid oscillations are the rule rather than the exception in biology.
I will now explain how the difference between coping styles of the two hemispheres accounts for anosognosia—the denial of disability, in this case paralysis. As we saw earlier, when either hemisphere is damaged by stroke the result is hemiplegia, a complete paralysis of one side of the body. If the stroke is in the left hemisphere, then the right side of the body is paralyzed, and as expected the patient will complain about the paralysis and request treatment. The same is true for a majority of right-hemisphere strokes, but a significant minority of patients remain indifferent. They play down the extent of the paralysis and stubbornly deny that they cannot move—or even deny ownership of a paralyzed limb! Such denial usually happens as a result of additional damage to the postulated “devil’s advocate” in the right hemisphere’s frontoparietal regions, which allows the left hemisphere to go into an “open loop,” taking its denials to absurd limits.
I recently examined an intelligent, sixty-year-old patient named Nora, who had an especially striking version of this syndrome.
“Nora, how are you today?” I asked.
