Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (44 page)

Even with the best survival techniques, and the highest of goals, the formula won’t always work. My friend Rob Hall, an expert mountaineer motivated by a desire to save a failing friend and inspired by a phone call to his pregnant wife, was unable to overcome that brutal storm on Everest. Rob was not so much a victim of the environment as of his genes. He could have outrun the storm if his priority had been only to save himself, but he was a human trying to save another of his species. Sacrificing oneself for the good of the species is pervasive in the animal world—we’ve seen the striking example of poison-dart frogs. But in higher animals the behavior requires a conscious decision. The cerebral cortex must override the powerful instinct for survival with an even more powerful signal of altruism. That signal is most intense when the genes in peril are the most similar—a parent ready to die for a child. It remains very strong within families and strong within ethnic groups, lessening gradually as genes become more dissimilar. A species-wide nongenetic version also exists—evident in a soldier’s loyalty to his country, or in an individual’s willingness to die for a principle.

Two thousand feet below Rob Hall, caught in the same storm, was another of my friends, Beck Weathers. Beck was lower down on the mountain than Rob, but nevertheless exposed to wind and cold incompatible with life. Oxygen-deprived, dehydrated, and exhausted, he collapsed in the snow. Helpless against the elements, his vital functions would slow, then stop. The sequence should have been inevitable. Beck lay in the snow for a day, a night, and a second day. His frozen body did shut down, but his mind did not. His life was reduced to thoughts—of his home and his family. He refused to die. Thoughts contain electricity. Strong thoughts contain more electricity. Beck’s will to survive generated enough power to reenergize his body, get him
up from the snow, and walk him out of the storm. But how and from where did that will arise?

To explore the source of the will to survive, we must take a journey into the human brain—a 2½-pound blob that generates a mere 25 watts of power. That’s barely enough to turn on a dim lightbulb, yet the brain contains more unexplained forces and uncharted territory than anyplace else on earth.

Humans aren’t the fastest or the strongest species; we’ve prevailed because we are the smartest. We’ve evolved the most complex brains, building on the same structures that lower animals possess but adding additional layers and innumerable interconnections in response to the demands of our surroundings.

The most primitive part of the brain is the brain stem, located at the bottom. Like any other stem, it’s where the roots come together—the roots being the nerves that branch into every part of the body. The nerves send electrical signals to the brain stem that provide constant updates on internal information such as heart rate, respiration, and blood pressure. External information, derived from nerves to our senses, enters the brain through a switching station called the thalamus. If the thalamus interprets the input as danger, it sends a warning signal to the amygdala—the emotion and fear center of the brain stem—which sounds the alarm, activating the body’s defensive reactions. Signals are sent back down the brain stem to increase heart rate and breathing and either to stand stock-still, or move muscles to begin an attack or effect an escape. The system is automatic and operates on an unconscious level. It is based on an ancient blueprint, and it’s equivalent to the entire brain of a reptile.

While the brains of reptiles have remained more or less the same for millions of years, the human brain has evolved dramatically from its ancient template. The biggest change has been the development of the cerebral cortex—the stuff that looks like a cauliflower and envelops the more primitive parts. It’s responsible for the higher signal processing necessary to evaluate sensory input more accurately and generate more precise and appropriate responses. This process takes time, so the
reptile’s system still has its uses—a fast reaction may save a life. But now the thalamus switching station has another place to send the signal. The cortex can override the initial reaction once it refines the sensory input, searches its memory, and determines that the curvy thing you just jumped away from wasn’t a snake but only a stick. The cortex can then send a signal to the amygdala to stop sounding the alarm, and your sense of fear will vanish instantly.

Since higher animals possess more cortex, they can process input more accurately, and consequently exhibit more intricate behavior. Each portion of the cortex is responsible for monitoring or controlling one function, such as vision, hearing, or movement. The sections must be linked, of course, so that physical actions are coordinated; otherwise a bird could look in one direction and fly in another. But in most animals, no matter how complex the linkage between the parts and how intricate the behavior, the effect of an outside stimulus will be automatic. Bears hibernate when it’s cold, and antelope flee when they see a lion. These unconscious responses to threats from the environment, though complex, are survival instincts.

The behavior will be routinely predictable unless some system overrides the signal. The most highly evolved animals have shown dramatic expansion of the front part of their cortex, the frontal lobes. This is a tertiary processing center, taking refined information from each section of the cortex and adding input from the centers that control memory and emotion. The frontal lobes evaluate each component and create a balance that is unique to each individual. They are able to alter prewired instinctual behavior. The evolution of this capability was the dawn of thinking.

Thinking requires a mind, a software program that fits into the hardwiring of the brain. The mind occupies the same space as the brain and is bound to its topography. Thoughts arise from specific locations and require energy to form. That’s why thinking can make you tired, but it’s also the key to mapping the brain with sensitive machines such as positron emission tomography (PET) scans and magnetic resonance imaging (MRI) that precisely localize and measure internal energy levels. If you hear a noise, your auditory cortex lights up. If you recognize the noise to be that of a lion, your memory
center lights up too. And if you’ve learned that lions are dangerous, your fear center lights up as well. Energy flows between the centers and on up to the frontal lobes, where information is synthesized. Frontal lobes develop options and make relative value judgments, but they don’t make decisions or supply motivation. If we relied on our frontal lobes alone to guide us, we’d be like the proverbial donkey who was equidistant between two bales of hay and starved to death because he couldn’t decide which one to eat.

Decisions require someone or something to take control and initiate action—a prime mover. The thinking involved leaves trails that can be followed. Energy flow can be traced from the frontal lobes to a small area lying deep within the cortex that lights up when decisions are made—at which point the flow then reverses, and a cascade of electrical impulses is sent back to the cortex, setting in motion all the functions needed for survival. This signal-generating area is called the anterior cingulate gyrus, or just cingulate, and it appears to be the brain’s commander-in-chief.

The cingulate is the decision maker and motivator that enables humans to act in a purposeful manner. Without the cingulate, the body languishes in a state of placid indifference. Consider the example of certain stroke victims, in whom the loss of blood supply to the brain has temporarily knocked out the cingulate. They become incapable of physically responding to the external stimuli that they receive. Once they recover the ability to communicate, they report that, although they were alert and aware, they didn’t feel any need to react. If they had heard or seen a lion coming, they would have recognized it and been afraid but wouldn’t have cared—a state not compatible with prolonged life. The cingulate may be the key to finding the origin of the will to survive.

Though it arises as a barely perceptible glow in the deepest recesses of the brain, the effect of will on survival is pervasive, dramatic, and sometimes powerful beyond our comprehension. It’s at work all along a continuum of environmental insults, large and small—anything that challenges a body venturing outside its familiar habitat, from horrific snowstorms to distasteful meals.

The bug-laden bowl of spaghetti served to me in the jungle represented
in its own little way a challenge to my survival. The image of a mass of long white strands covered with black dots was transmitted from my eyes to my thalamus switching station. Not seeing an urgent threat, the image was directed to the visual cortex for further analysis. It was confirmed to be bug-laden spaghetti, and the information was passed up to the frontal lobes. There, my memory center was tapped, and it reminded me that I don’t eat bugs. My emotion center added its two cents by generating feelings of nausea. My information package was complete. Were I at home, I’d have thrown the food away. But a second competing package had formed as well. This one provided input from my brain stem telling me my blood sugar was low, so I was hungry. My senses reminded me I was in the jungle, and my memory added that the bugs weren’t poisonous. My cingulate weighed the two options and chose to favor my survival; it directed me to eat. It then signaled the motor center of the cortex to coordinate the activity. For good measure, the cingulate also sent a countersignal to my emotion centers to suppress my nausea. The jungle setting had summoned in my brain enough will to change my behavior.

At Antonio’s hut, however, I could not take a single bite out of a boiled rat head with its hair still on. In that instance, powerful input from the emotions took command of the cingulate’s efforts to manage the options of hunger or satiety. Had I been starving, I might have been able to summon the additional will required to partake, but survival was not at stake and my will was fully suppressed by my revulsion. I could eat the spaghetti but not the rat.

It’s no surprise that emotions can easily override logic. We see examples of it every day in ourselves and others, like my patient who broke his hand when he found a ticket on the windshield of his car and punched the parking meter. Emotions can prevail over reasoning because the pathways from the amygdala emotion center to the cingulate decision center are very well developed. They carry more signal traffic, and thus more influence, than the less developed pathways that go in the other direction. Emotional impulses can overwhelm the capacity for reasoning far more easily than logical control can be exerted over primitive responses. Evolution, however, is a work in progress:
higher animals are evolving more connections from cingulate to amygdala, and therefore more control over emotions. Nevertheless, even in humans, the amygdala often still rules.

The plane crash high in the Andes that stranded the Uruguayan rugby team for months forced the survivors into a struggle between their frontal lobes and their amygdalas. Facing starvation, they lived by eating their dead teammates—an excellent food source according to frontal lobe analysis, and the obvious choice for any cingulate. Cannibalism, however, generates a high-intensity signal of revulsion from the amygdala. It’s an adaptation, like altruism, that favors survival of the species over the individual. It would be difficult to organize a society if its members always looked at each other as potential meals. People who are able to generate a counterimpulse to squelch the amygdala are those whose will to survive is strong enough to override cultural and emotional considerations. The same tormented decisions determined the fate of the shipwrecked crews of the
Essex
and
Mignonette
and the snow-trapped settlers in the Donner Party.

For each person in each of these cases, the mind made a decision as to whether or not the organism wanted to survive. If the will is there, the brain initiates actions that are appropriate responses to the environmental stress. Sometimes, though, the brain initiates a response that is “inappropriate” but more favorable for survival. The mind is able to abrogate the laws of physiology and command responses that seem to break the rules—to “cheat” in order to aid its own survival.

A pain in the neck is the annoyingly predictable result of any cool breeze that reaches me through an open window at home. Yet I spent a month exposed to the frigid winds of Antarctica and my neck didn’t even notice. In that extreme environment, I subconsciously rejected any thought that would have compromised my ability to function. How is this possible? What’s the trick here? From what we’ve seen so far, the answer would seem obvious: some signal is sent to suppress the pain center. Except that there is no pain center in the brain. Pain signals are received in the same way as touch or temperature, except that the readings fall outside the body’s safe range. Pain input is nothing
more than a reporting of facts, but the body has to react to the data quickly to avoid damage. The surest way to do this is to create an unpleasant sensation, a distinct second step that requires stimulating both attention and emotion centers. Unless both are activated, the body won’t feel any conscious need to respond. Emotion centers have thresholds dependent on the nature of the individual (e.g., tough guys are more stoic, sometimes) and on cultural considerations (e.g., Sherpas never complain that their feet are cold). If the level of pain activates the emotion center, the signal gets passed on to the frontal lobes where it will compete with innumerable other signals for the brain’s attention. The cingulate will then determine the appropriate strategy and evoke the proper protective behavior. For me in subzero temperatures, the answer was easy. My brain had more than enough input to know it was extremely cold. My attention center was fully occupied with the problem, making appropriate behavioral and internal body responses to keep me alive. At home, the awareness of a cold neck would motivate me to close the window or get a scarf, but here it would not change my behavior, so my brain rejected the pain before it reached the conscious level where it would become a distraction. In the hostile climate of Antarctica, I literally didn’t have time for the pain.