The Tell-Tale Brain: A Neuroscientist’s Quest for What Makes Us Human
by V.S. Ramachandran
Norton, 357 pp., $26.95
Is studying the brain a good way to understand the mind? Does psychology stand to brain anatomy as physiology stands to body anatomy? In the case of the body, physiological functions—walking, breathing, digesting, reproducing, and so on—are closely mapped onto discrete bodily organs, and it would be misguided to study such functions independently of the bodily anatomy that implements them. If you want to understand what walking is, you should take a look at the legs, since walking is what legs do. Is it likewise true that if you want to understand thinking you should look at the parts of the brain responsible for thinking?
Is thinking what the brain does in the way that walking is what the body does? V.S. Ramachandran, director of the Center for Brain and Cognition at the University of California, San Diego, thinks the answer is definitely yes. He is a brain psychologist: he scrutinizes the underlying anatomy of the brain to understand the manifest process of the mind. He approvingly quotes Freud’s remark “Anatomy is destiny”—only he means brain anatomy, not the anatomy of the rest of the body.
But there is a prima facie hitch with this approach: the relationship between mental function and brain anatomy is nowhere near as transparent as in the case of the body—we can’t just look and see what does what. The brain has an anatomy, to be sure, though it is boneless and relatively homogeneous in its tissues; but how does its anatomy map onto psychological functions? Are there discrete areas for specific mental faculties or is the mapping more diffuse (“holistic”)?
The consensus today is that there is a good deal of specialization in the brain, even down to very fine-grained capacities, such as our ability to detect color, shape, and motion—though there is also a degree of plasticity. The way a neurologist like Ramachandran investigates the anatomy–psychology connection is mainly to consider abnormal cases: patients with brain damage due to stroke, trauma, genetic abnormality, etc. If damage to area A leads to disruption of function F, then A is (or is likely to be) the anatomical basis of F.
This is not the usual way that biologists investigate function and structure, but it is certainly one way—if damage to the lungs hinders breathing, then the lungs are very likely the organ for breathing. The method, then, is to understand the normal mind by investigating the abnormal brain. Brain pathology is the key to understanding the healthy mind. It is as if we set out to understand political systems by investigating corruption and incompetence—a skewed vision, perhaps, but not an impossible venture. We should judge the method by the results it achieves.
Ramachandran discusses an enormous range of syndromes and topics in The Tell-Tale Brain. His writing is generally lucid, charming, and informative, with much humor to lighten the load of Latinate brain disquisitions. He is a leader in his field and is certainly an ingenious and tireless researcher. This is the best book of its kind that I have come across for scientific rigor, general interest, and clarity—though some of it will be a hard slog for the uninitiated. In what follows I can only provide a glimpse of the full range of material covered, by selecting a sample of case studies.
We begin with phantom limbs—the sensation that an amputated or missing limb is still attached to the body. Such limbs can arrange themselves intransigently into painful positions. The doctor touches the patient’s body in different parts with a cotton swab, eliciting normal responses; then he touches the patient’s face and elicits sensations in the patient’s phantom hand, finding an entire map of the absent hand on the patient’s face. Why? Because in the strip of cortex called the postcentral gyrus the areas that deal with nerve inputs from the hand and face happen to be adjacent, so that in the case of amputation some sort of neighborly cross-activation occurs—the facial inputs spill over to the area that maps the phantom hand.
A contingency of anatomy therefore gets reflected in a psychological association; if the hand area of the brain had been next to the foot area, then tickling the foot might have caused a tickling sensation in the phantom hand. In another patient, amputation of the foot leads to sensations from the penis being felt in the phantom foot, including orgasm. Ramachandran devises a method to enable patients to move their paralyzed phantom arms, by using a mirror that simulates seeing the absent arm by reflecting the remaining arm: the brain is fooled into believing that the arm is still there and lets the patient regain control of its position. There are even cases in which the mirror device enables a patient to amputate a phantom arm, so that he no longer suffers the illusion of possessing it.
The chapter on vision covers such topics as visual illusion, the inferential character of seeing, blindsight, and the Capgras delusion, by which friends or relatives are seen as impostors. In blindsight an apparently blind patient can make correct visual judgments, thus demonstrating that visual information is still being received somewhere in the damaged brain. As Ramachandran explains it, this is the result of two visual pathways—the so-called old and new pathways—that can operate independently: the new pathway from the eyes is destroyed and with it conscious visual awareness, but the old pathway remains intact and conveys information unconsciously. Thus the patient takes herself to be quite blind, while still registering some visual information. The underlying anatomy of vision possesses a surprising duality of which most of us are never aware, and the upshot is the odd condition of blindsight.
In the rare Capgras syndrome a person will become convinced that close relatives are impostors, thinking that the real mother (say) is some sort of fraudulent twin. The sufferer’s eyes are working perfectly and have no difficulty recognizing the relative, but there is a stubborn conviction that this is not really her. Ramachandran explains this oddity as arising from a lack of nerve connection between the face recognition part of the brain and the amygdala, which deals with emotional response: since the perceived individual does not arouse the usual affective response, she cannot be the real mother, so the brain manufactures the notion that she must be an impostor. The explanation of the syndrome is thus anatomical, not psychological—a disruption in the normal neural connections.
Next we pass to “Loud Colors and Hot Babes: Synesthesia,” a chapter I found especially rich. First Ramachandran has to provide proof that the phenomenon of synesthesia—in which stimulating one sense evokes stimulation in another, as when hearing a sound produces the visualization of a color—is real and that experiencing numbers as colored is not just a matter of childhood associations or vague metaphor. This he does by demonstrating that perceptual grouping of numerals can occur according to the color experiences the numbers evoke. He shows that the colors enter the mind as genuine sensations.
Then there is the difficult question of what explains synesthesia: Why should some people exhibit such an odd confluence of sensations? The answer again comes from anatomical propinquity: a main color center of the brain, V4, in the temporal lobes, is right next to an area dedicated to number processing—so synesthesia is conjectured to arise from cross-wiring of neurons. When a person with synesthesia perceives numerals there is an abnormal crossing over of nerve activity into the adjacent color area of the brain; the two areas are not insulated from each other, as they are in most people. One brain area excites the other, despite the lack of objective link between numbers and colors. In fact, it is surprising that this kind of thing doesn’t happen more often in the brain, because electrical potentials could easily spread from one area to another without something to damp things down.
More speculatively, Ramachandran ponders the connection between synesthesia and creativity, especially metaphor, conjecturing that it might be the basis of creativity. (It is found more commonly in creative artists: Nabokov was a synesthete; as a boy, he recalled, he associated the number five with the color red.) In a stylistically typical sentence Ramachandran writes: “Thus synesthesia is best thought of as an example of subpathological cross-modal interactions that could be a signature or marker for creativity.”
This leads him to the hypothesis that the fundamental mechanism of synesthesia might be shared by non-synesthetes, because of what he calls “cross-modal abstraction.” If you present subjects with two shapes, one rounded and one jagged, and ask them which of the shapes is called “bouba” and which “kiki,” you find that a majority assigns “bouba” to the rounded stimulus and “kiki” to the jagged one—as if some abstract form unites the sight and the sound. Ramachandran suggests that this is because the tongue makes different movements for the two sounds, which resemble the presented shapes. This “bouba-kiki effect” is held, by him, to explain, at least in part, the evolution of language, metaphor, and abstract thought—because, as we shall see, it involves purely structural similarities or analogies.
In a chapter boldly entitled “The Neurons That Shaped Civilization,” Ramachandran invests the famous “mirror neurons” (discovered in the 1990s) with remarkable generative powers. The mirror neurons that have been identified in the brain serve as the mechanism of imitation, he suggests, in virtue of their ability to react or “fire” sympathetically, and thus affect consciousness, when you are watching someone else do something: some of the same neurons fire both when you observe the performance of an action and when you actually perform that action. This is held to show that the brain automatically produces a representation of someone else’s “point of view”—it runs by means of mirroring neurons an internal simulation of the other’s intended action.
Observing that we are a species much talented in the art of imitation, Ramachandran suggests that mirror neurons enable us to absorb the culture of previous generations:
Culture consists of massive collections of complex skills and knowledge which are transferred from person to person through two core mediums, language and imitation. We would be nothing without our savant-like ability to imitate others.
The mirror neurons act like sympathetic movements that can occur when watching someone else perform a difficult task—as when your arm swings slightly when you watch someone hit a ball with a bat. For Ramachandran this specific neural circuitry provides the key to understanding the growth of culture; indeed, the mirror neurons are held to permit the evolution of language, by enabling imitative utterance. According to him, we need special inhibitory mechanisms in order to keep our mirror neurons under control—or else we would be in danger of doing everything we see and losing our sense of personal identity. We are, in effect, constantly impersonating others at a subconscious level, as our hyperactive mirror neurons issue their sympathetic reactions. Ramachandran sees a connection between the bouba-kiki effect and mirror neurons, in that both involve the exploitation of abstract mappings—across sense modalities in the former case or from perceptual to motor in the latter.