The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

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.

“Fine, Sir, except the hospital food. It’s terrible.”

“Well, let’s take a look at you. Can you walk?”

“Yes.” (Actually, she hadn’t taken a single step in the last week.)

“Nora, can you use your hands, can you move them?”

“Yes.”

“Both hands?”

“Yes.” (Nora had not used a fork in a week.)

“Can you move your left hand?”

“Yes, of course.”

“Touch my nose with your left hand.”

Nora’s hand remains motionless.

“Are you touching my nose?”

“Yes.”

“Can you see your hand touching my nose?”

“Yes, it’s now almost touching your nose.”

A few minutes later I grabbed Nora’s lifeless left arm, raised it toward her face, and asked, “Whose hand is this, Nora?”

“That’s my mother’s hand, Doctor.”

“Where is your mother?”

At this point Nora looked puzzled and glanced around for her mother. “She is hiding under the table.”

“Nora, you said you can move your left hand?”

“Yes.”

“Show me. Touch your own nose with your left hand.”

Without the slightest hesitation Nora moved her right hand toward her flaccid left hand, grabbed it and used it like a tool to touch her nose. The amazing implication is that even though she was denying that her left arm was paralyzed, she must have known at some level that it was, for if not, why would she spontaneously reach out to grab it? And why does she use “her mother’s” left hand as a tool to touch her own nose? It would appear that there are many Noras within Nora.

Nora’s case is an extreme manifestation of anosognosia. More commonly the patient tries to play down the paralysis, rather than engaging in outright denial or confabulation. “No problem, Doc. It’s getting better every day!” Over the years I have seen many such patients and been struck by the fact that many of their comments bear a striking resemblance to the kinds of everyday denials and rationalizations that we all engage in to tide over the discrepancies in our daily lives. Sigmund (and more especially his daughter Anna) Freud referred to these as “defense mechanisms,” suggesting that their function is to “protect the ego”—whatever that means. Examples of such Freudian defenses would include denial, rationalization, confabulation, reaction formation, projection, intellectualization, and repression. These curious phenomena have only a tangential relevance to the problem of Consciousness (with a big C), but—as Freud urged—they represent the dynamic interplay of between the conscious and unconscious, so studying them may indirectly illuminate our understanding of consciousness and other related aspects of human nature. So I’ll list them.

1. Outright denial—“My arm isn’t paralyzed.”

2. Rationalization—The tendency we all have to ascribe some unpleasant fact about ourselves to an external cause: For example, we might say, “The exam was too hard” rather than “I didn’t study hard enough,” or “The professor is sadistic” rather than “I am not smart.” This tendency is amplified in patients.

For example, when I asked a patient, Mr. Dobbs, “Why are you not moving your left hand like I asked you to?” his replies varied:

“I am an army officer, Doctor. I don’t take orders.”

“The medical students have been testing me all day. I am tired.”

“I have severe arthritis in my arm; it’s too painful to move.”