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

by V.S. Ramachandran

explicable. Often when a clinical mystery is solved, the explanation reveals something new about how the normal, healthy brain works, and yields unexpected insights into

some of our most cherished mental faculties.

Revolutions occurred in surgery, pharmacology, and public health, and human life spans in the developed world doubled in the space of just four or five generations.

By comparison, the sciences of the mind—psychiatry, neurology, psychology—languished for centuries.

Is this perhaps the secular humanists’ version of original sin?

As the great biologist Theodosius Dobzhansky said, “Nothing in biology makes sense except in the light of evolution.”

But in biological systems there is a deep unity between structure, function, and origin. You cannot make very much progress understanding any one of these unless you are also paying close attention to the other two.

Feathers evolved from scales whose original role was insulation rather than flight. The

Evolution found ways to radically repurpose many functions of the ape brain to create entirely new functions. Some of them—language comes to mind—are so powerful that I would go so far as to argue they have produced a species that transcends apehood to the same degree by which life transcends mundane chemistry and physics.

The next triad of chapters investigates a type of nerve cell that I argue is especially crucial in making us human. Chapter 4 introduces these special cells,

called mirror neurons,

the most challenging problem of all, the nature of self-awareness, which is undoubtedly unique to humans.

Speaking of accuracy, let me be the first to point out that some of the ideas I present in this book are, shall we say, on the speculative side. Many of the chapters rest on solid foundations, such as my work on phantom limbs, visual perception, synesthesia, and the Capgras delusion. But I also tackle a few elusive and less well-charted topics, such as the origins of art and the nature of self-awareness. In such cases I have let educated guesswork and intuition steer my thinking wherever solid empirical data are spotty. This is nothing to be ashamed of: Every virgin area of scientific inquiry must first be explored in this way. It is a fundamental element of the scientific process that when data are scarce or sketchy and existing theories are anemic, scientists must brainstorm. We need to roll out our best hypotheses, hunches, and hare-brained, half-baked intuitions, and then rack our brains for ways to test them. You see this all the time in the history of science. For instance, one of the earliest models of the atom likened it to plum pudding, with electrons nested like plums in the thick “batter” of the atom. A few decades later physicists were thinking of atoms as miniature solar systems, with orderly electrons that orbit the nucleus like planets around a star. Each of these models was useful, and each got us a little bit closer to the final (or at least, the current) truth.

Never take the obvious for granted.

Hippocrates, Sushruta, my ancestral sage Bharadwaja, or any other physicians between ancient times and the present could have performed these same basic experiments. Yet no one did.

Homogeneity breeds weakness: theoretical blind spots, stale paradigms, an echo-chamber mentality, and cults of personality.

My point is that science should be question driven, not methodology driven.

“When the only tool you have is a hammer, everything starts to look like a nail.”

I find it odd how some people are so ardently drawn to either-or dichotomies. “Are apes self-aware or are they automata?” “Is life meaningful or is it meaningless?” “Are humans ‘just’ animals or are we exalted?”

As a scientist I am perfectly comfortable with settling on categorical conclusions—when it makes sense. But with many of these supposedly urgent metaphysical dilemmas, I must admit I don’t see the conflict. For instance, why can’t we be a branch of the animal kingdom and a wholly unique and gloriously novel phenomenon in the universe?

Especially awe inspiring is the fact that any single brain, including yours, is made up of atoms that were forged in the hearts of countless, far-flung stars billions of years ago. These particles drifted for eons and light-years until gravity and chance brought them together here, now.

These atoms now form a conglomerate—your brain—that can not only ponder the very stars that gave it birth but can also think about its own ability to think and wonder about its own ability to wonder. With the arrival of humans, it has been said, the universe has suddenly become conscious of itself. This, truly, is the greatest mystery of all.

Are our brains uniquely hardwired for empathy and compassion?

They can occur in social systems, for example, where millions of individual decisions or attitudes can interact to rapidly shift the entire system into a new balance.

Phase transitions are afoot during speculative bubbles, stock market crashes, and spontaneous traffic jams. On a more positive note, they were on display in the breakup of the Soviet Bloc and the exponential rise of the Internet. I would even suggest that phase transitions may apply to human origins.

consciousness

Didn't we have conciousness before then?

Fortunately, underlying all this lyrical complexity there is a basic plan of organization that’s easy to understand. Neurons are connected into networks that can process information. The brain’s many dozens of structures are ultimately all purpose-built networks of neurons, and often have elegant internal organization. Each of these structures performs some set of discrete (though not always easy to decipher) cognitive or physiological functions. Each structure makes patterned connections with other brain structures, thus forming circuits. Circuits pass information back and forth and in repeating loops, and allow brain structures to work together to create sophisticated perceptions, thoughts, and behaviors.

The flow of information is thus always unidirectional.

Running up and down the core of the spinal column is a thick bundle of nerve fibers—the spinal cord—that conducts a steady stream of messages between brain and body. These messages include things like touch and pain flowing up from the skin, and motor commands rat-a-tat-tatting down to the muscles.

The medulla and nuclei (neural clusters) on the floor of the pons control important vital functions like breathing, blood pressure, and body temperature. A hemorrhage from even a tiny artery supplying this region can spell instant death.

Why we need a relay station is far from clear.

Why

strangely

Damage to cells in the basal ganglia results in disorders like Parkinson’s disease, in which the patient’s torso is stiff, his face is an expressionless mask, and he walks with a characteristic shuffling gait. (Our neurology professor in medical school used to diagnose Parkinson’s by just listening to the patient’s footsteps next door; if we couldn’t do the same, he would fail us. Those were the days before high-tech medicine and magnetic resonance imaging, or MRI.)

brain chemical dopamine

The temporal lobes are specialized for higher perceptual functions, such as recognizing faces and other objects and linking them to appropriate emotions.

In addition to all this, the upper part of the left temporal lobe contains a patch of cortex known as Wernicke’s area. In humans this area has ballooned to seven times the size of the same area in chimpanzees; it is one of the few brain areas that can be safely declared unique to our species. Its job is nothing less than the comprehension of meaning and the semantic aspects of language—functions that are prime differentiators between human beings and mere apes.

So great was this expansion that at some point in our past a large portion of it split into two new processing regions called the angular gyrus and the supramarginal gyrus. These uniquely human areas house some truly quintessential human abilities.

In fact, if you zap the right angular gyrus with an electrode, you will have an out-of-body experience.

Yet he has lost many of the most quintessential attributes that define human nature: ambition, empathy, foresight, a complex personality, a sense of morality, and a sense of dignity as a human being. (Interestingly, a lack of empathy, moral standards, and self-restraint are also frequently seen in sociopaths, and the neurologist Antonio Damasio has pointed out they may have some clinically undetected frontal dysfunction.)

For these reasons the prefrontal cortex has long

been regarded as the “seat of...

I mentioned three of these areas above: Wernicke’s area in the left temporal lobe, the prefrontal cortex, and the IPL in each parietal lobe.

Within some of these regions, there is a special class of nerve cells called mirror neurons. These neurons fire not only when you perform an action, but also when you watch someone else perform the same action. This sounds so simple that its huge implications are easy to miss. What these cells do is effectively allow you to empathize with the other person and “read” her intentions—figure

out what she is really up to. You do this by running a simulation of her actions using your own body image.

but usually your mirror neurons are reasonably accurate guessers of others’ intentions. As such, they are the closest thing to telepathy that nature was able to endow us with.

These abilities (and the underlying mirror-neuron circuitry) are also seen in apes, but only in humans do they seem to have developed to the point of being able to model aspects of others’ minds rather than merely their actions.

Deciphering the nature of these connections—rather than just saying, “It’s done by mirror neurons”—is one of the major goals of current brain research.

By hyper-developing the mirror-neuron system, evolution in effect turned culture into the new genome. Armed with culture, humans could adapt to hostile new environments and figure out how to exploit formerly inaccessible or poisonous food sources in just one or two generations—instead of the hundreds or thousands of generations such adaptations

would have taken to accomplish through genetic evolution.