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

by V.S. Ramachandran

We might as well call ourselves Homo plasticus.

While other animal brains exhibit plasticity, we are the only species to use it as a central player in brain refinement and evolution. One of the major ways we managed to leverage neuroplasticity to such

stratospheric heights is known as neoteny—our almost absurdly prolonged infancy and youth, which leaves us both hyperplastic and hyperdependent on ...

Perception is an actively formed opinion of the world rather than a passive reaction to sensory input from it.

It’s as if each of us is hallucinating all the time and what we call perception involves merely selecting the one hallucination that best matches the current input. This

face. The question of how neurons encode meaning and evoke all the semantic associations of an object is the holy grail of neuroscience, whether you are studying memory, perception, art, or consciousness.

The old pathway, on the other hand, is apparently performing equally complex computations to guide the hand, but without a wisp of consciousness creeping in. This is one reason why I likened this pathway to a robot or a zombie. Why should this be so? After all, they are just two parallel pathways made up of identical-looking neurons, so why is only one of them linked to conscious awareness? Why indeed. While I have raised it here as a teaser, the question of conscious awareness is a big one that we will leave for the final chapter.

This disorder is called agnosia, a term coined by Sigmund Freud meaning that the patient sees but doesn’t know.

The notion that synesthesia is just metaphor illustrates one of the classic pitfalls in science—trying to explain one mystery (synesthesia) in terms of another (metaphor).

And for that matter, you can never truly know whether other people’s inner mental experience of redness is the same as yours. This makes it somewhat tricky (to put it mildly) to study the perception of other people.

Out, out, brief candle! Life’s but a walking shadow, a poor player That struts and frets his hour upon the stage, And then is heard no more. It is a tale Told by an idiot, full of sound and fury, Signifying nothing.

Schizophrenics, who have miswired brains, are terrible at interpreting metaphors and proverbs. Yet according to clinical folklore, they are very good at puns.

puzzle. It would be arrogant for a scientist to deny that there are still many important questions about the evolution of the human mind and brain that remain unanswered.

this “Wallace’s problem”

The lowest savages with the least copious vocabularies [have] the capacity of uttering a variety of distinct articulate sounds and of applying them to an almost infinite amount of modulation and inflection [which] is not in any way inferior to that of the higher [European] races. An instrument has been developed in advance of the needs of its possessor.

inferior parietal lobule

Finally, only in humans do we see a major portion of this lobule splitting further into two, the angular gyrus and the supramarginal gyrus, suggesting that something important was going on in this region of the brain during human evolution.

The upper part of the IPL, the supramarginal gyrus, is another structure unique to humans. Damage here leads to a disorder called ideomotor apraxia: a failure to perform skilled actions in response to the doctor’s commands. Asked to pretend he is combing his hair, an apraxic will raise his arm, look at it, and flail it around his head. Asked to mime hammering a nail, he will make a fist and bang it on the table. This happens even though his hand isn’t paralyzed (he will spontaneously scratch an itch) and he knows what “combing” means (“It means I am using a comb to tidy up my hair, Doctor”). What he lacks is the ability to conjure up a mental picture of the required action—in this case combing—which must precede and orchestrate the actual execution of the action. These are functions one would normally associate with mirror neurons, and indeed the supramarginal gyrus has mirror neurons. If our speculations are on the right track, then one would expect patients with apraxia to be terrible at understanding and imitating other people’s movements.

Their mirror-neuron system is either not advanced enough or is not adequately connected to other brain structures to allow the rapid propagation of culture.

This devastating developmental disorder was discovered independently by two physicians, Leo Kanner in Baltimore and Hans Asperger in Vienna, in the 1940s. Neither doctor had any knowledge of the other, and yet by an uncanny coincidence they gave the syndrome the same name: autism.

“theory of mind”

It refers to your ability to attribute intelligent mental beingness to other people: to understand that your fellow humans behave the way they do because (you assume) they have thoughts, emotions, ideas, and motivations of more or less the same kind as you yourself possess. In other words, even though you cannot actually feel what it is like to be another individual, you use your theory of mind to automatically project intentions, perceptions, and beliefs into the minds of others. In so doing you are able to infer their feelings and intentions and to predict and influence their behavior.

A third possibility—one that I suggested in an article for Scientific American that I coauthored with my graduate student Lindsay Oberman—would be to try certain drugs. There is a great deal of anecdotal evidence that MDMA (the party drug ecstasy) enhances empathy, which it may do by increasing the abundance of neurotransmitters called empathogens, which naturally occur in the brains of highly social creatures such as primates. Could a deficiency in such transmitters contribute to the symptoms of autism? If so, could MDMA (with its molecule suitably modified) ameliorate some of the most troubling symptoms of the disorder? It is also known that prolactin and oxytocin—so-called affiliation hormones—promote social bonding. Perhaps this connection, too, could be exploited therapeutically. If administered sufficiently early, cocktails of such drugs might help tide over some early symptom manifestations enough to minimize the subsequent cascade of events that lead to the full spectrum of autistic symptoms.

Autism reminds us that the uniquely human sense of self is not an “airy nothing” without “habitation and a name.” Despite its vehement tendency to assert its privacy and independence, the self actually emerges from a reciprocity of interactions with others and with the body it is embedded in. When it withdraws from society and retreats from its own body it barely exists; at least not in the sense of a mature self that defines our existence as human beings. Indeed, autism could be regarded fundamentally as a disorder of self-consciousness, and if so, research on this disorder may help us understand the nature of consciousness itself.

I took the handle of my knee hammer and, while Dr. Hamdi was lying in bed, stroked the outer border of his right foot and then the left foot, running the tip of the hammer handle from the pinky to sole. Nothing much happened in the normal foot, but when I repeated the procedure on the paralyzed right foot, the big toe instantly curled upward and all the other toes fanned out. This is Babinski’s sign, arguably the most famous sign in neurology. It reliably indicates damage to the pyramidal tracts, the great motor pathway that descends from the motor cortex down into the spinal cord conveying commands for volitional movements.

TWO TOPICS IN brain research always seem to attract geniuses and crackpots. One is consciousness and the other is the question of how language evolved. So many zany ideas on language origins were being proposed in the nineteenth century that the Linguistic Society of Paris introduced a formal ban on all papers dealing with this topic.

(As Francis Crick once said, “God is a hacker, not an engineer.”)

call it the “synesthetic bootstrapping theory.”

No medical student who believed in “general health” as a monolithic entity would get very far in medical school or be allowed to become a physician—and rightly so—and yet whole careers in psychology and political movements have been built on the equally absurd belief in single measurable general intelligence. Their contributions have little more than shock value.

What do we mean by “knowledge” or “understanding”? And how do billions of neurons achieve them? These are complete mysteries. Admittedly, cognitive neuroscientists are still very vague about the exact meaning of words like “understand,” “think,” and indeed the word “meaning” itself. But it is the business of science to find answers step by step through speculation and experiment. Can we approach some of these mysteries experimentally? For instance, what about the link between language and thinking? How might you experimentally explore the elusive interface between language and thought?

It feels as if we do this kind of thinking visually and not by using language. But we have to be careful with this deduction because introspection about what’s going in one’s head (stacking the three boxes) is not a reliable guide to what’s actually going on.

Here are the names of my nine laws of aesthetics: Grouping Peak shift Contrast Isolation Peekaboo, or perceptual problem solving Abhorrence of coincidences Orderliness Symmetry Metaphor

So with the three overarching principles of internal logic, evolutionary function, and neural mechanics in mind, let’s see the role each of my individual laws plays in constructing a neurobiological view of aesthetics.

In a modern urban environment, objects are so commonplace that we don’t realize vision is mainly about detecting objects so that you can avoid them, dodge them, chase them, eat them, or mate with them.

Each of us carries templates for members of the opposite sex (such as your mother or father, or your first really sizzling amorous encounter), and maybe those whom you find inexplicably and disproportionately attractive later in life are ultranormal versions of these early prototypes.

On this one point I am in complete agreement with Freud.

experiments. Before him, people “knew” that if a heavy stone and a peanut were dropped simultaneously from the top of a tower, the heavier one would obviously fall faster. All it took was a five-minute experiment by Galileo to topple two thousand years of wisdom.

Art is the accomplishment of our desire to find ourselves among the phenomena of the external world.

In an ironic twist, once Nadia reached adolescence, she became less autistic. She also completely lost her ability to draw.

“Well, they zapped the student’s brains with a magnet, and suddenly these students could effortlessly produce beautiful sketches. And in one case the student could generate prime

numbers the same way some idiot savants do.”

I must confess I had (and still have) two very different reactions to this discovery. The first is sheer incredulity and skepticism. The observation doesn’t contradict anything we know in neurology (partly because we know so little), but it sounds outlandish. The very notion of some skill being enhanced by knocking out parts of the brain is bizarre—the sort of thing you would expect to see on The X-Files. It also smacks of the kind of pep talk you hear from motivational gurus who are forever telling you about all your hidden talents waiting to be awakened by purchasing their tapes. Or drug peddlers claiming their magic potions will elevate your mind to whole new dimensions of creativity and imagination. Or that absurd but tenaciously popular factoid about how people only use 10 percent of their brains—whatever that’s supposed to mean. (When reporters ask me about the validity of this claim, I usually tell them, “Well, that’s certainly true here in California.”)

Indeed, the line between perceiving and hallucinating is not as crisp as we like to think. In a sense, when we look at the world, we are hallucinating all the time. One could almost regard perception as the act of choosing the one hallucination that best fits the incoming data, which is often fragmentary and fleeting. Both hallucinations and real perceptions emerge from the same set of processes. The crucial difference is that when we are perceiving, the stability of external objects and events helps anchor them. When we hallucinate, as when we dream or float in a sensory deprivation tank, objects and events wander off in any direction.

Clérambault syndrome,

Koro, the alleged disorder said to afflict Asian gentlemen who claim that their penis is shrinking and will eventually wither away.

Another pseudomalady, again officially recognized, is “chronic under-achievement syndrome”—what used to be called stupidity.

Romantic love is a minor form of folie à deux, a mutual delusional fantasy that often afflicts otherwise normal people.

world. Here I will consider the relevance of this to understanding anosognosia, the denial of paralysis seen in some stroke patients. Speaking more generally, it can help us understand why even most normal people—including you and me—engage in minor denials and rationalizations to cope with the stresses of our daily lives.

Out of curiosity I irrigated his left ear canal with ice water. This procedure is known to activate the vestibular system and can provide a certain jolt to the body image; it can, for example, fleetingly restore awareness of the paralysis of the body to a patient with anosognosia due to a parietal stroke. When I did this for Patrick, he was astonished to notice the twin shrinking in size, moving, and changing posture. Ah, how little we know about the brain!

cases. On one particular evening after giving a lecture, I found Dr. Santhanam waiting for me in my office with a patient, a disheveled, unshaven young man of thirty named Yusof Ali. Ali had suffered