Ramachandran shows brain damage cases that caused patients various disorders in themselves. He says, “Philosophers have argued for centuries that if there is any one thing about our existence that is completely beyond question, it is the simple fact that ‘I’ exist as a single human being who endures in space and time. But even this basic axiomatic foundation of human existence is called into question by these patients.”(Ramachandran, p. 173)
At first, he shows that both the left hemisphere and the right one can have their own different "wills". He states, "A woman's left hand would fly up to her throat and try to strangle her. She often had to use her right hand to wrestle the left hand under control. … Kurt Goldstein thought that this woman's right hemisphere (which controlled her left hand) seemed to have some latent suicide tendencies. Initially these urges may have been held in check by brakes---inhibitory messages sent across the corpus callosum (脳梁)from the more rational left hemisphere. But if she had suffered damage to the corpus callosum as the result of stroke, that inhibition would be removed. The right side of her brain and its murderous left hand were now free to attempt to strangle her. … In fact, she had suffered a massive stroke in her corpus callosum." (ibid, pp. 12-13)
Ramachandran became famous for his studies on phantom limbs. The phantom limb was known to Descartes, who used it as evidence that our knowledge about our own body was uncertain. After Lord Nelson lost his right arm, he experienced phantom limb pain. He thought that his phantom pain was direct evidence for the existence of the soul. Because an arm could exist after it was removed, the whole person would be able to survive physical annihilation of the body. (ibid, pp. 22-23)
A phantom limb is a common phenomenon, but scientists don't know its physical cause or its treatment. Ramachandran was the first neuroscientist that discovered relationship between a phantom limb and brain mechanisms.
We have a representation of the body surface on the surface of the brain. It is called Penfield's somatosensory(体性感覚) homunculus, or map. But the map is not entirely continuous, unlike human body. For example, on the map the face is not near the neck, but is below the hand. So the hand is between the shoulder and the face on the map.
Ramachandran thought that in a phantom limb patient's brain, other body parts would use the somatosensory nerves that corresponded to the lost limb. When he touched a patient's cheek, the patient began to feel his cheek touched and also his phantom finger touched. He found that on the map there were two areas, face and upper arm, which corresponded to a phantom hand. He showed that a phantom limb is not an illusion of a patient, but has its physical cause in the brain. A patient said to Ramachandran, "My phantom hand sometimes itches like crazy, and I never know what to do about it. But now I know exactly where to scratch." (ibid, p. 38)
Next, Ramachandran tries to explain and cure phantom limb pain. There was a patient who could move his phantom hand. With his phantom hand he could feel gripping a cup placed two feet away. When Ramachandran wrenched a real cup from phantom fingers, the patient yelled, "ouch!" The fingers were illusionary, but the pain was real. (ibid, p. 43) Ramachandran began to think about the role of vision in sustaining the phantom limb experience.
When an actual limb is paralyzed, the brain sends its usual commands---"Move that arm." The command is monitored by the parietal lobe(頭頂葉), but it does not receive the proper visual feedback. The visual system says, "The arm is not moving". Eventually the brain learns that the arm does not move and a kind of "learned paralysis" is stamped onto the brain's circuitry. After the amputation of a paralyzed, painful limb, the patient experiences a vivid phantom of this limb. (ibid, 45-46) Learning by the visual system caused a phantom limb paralysis.
Ramachandran devised a mirror box where a patient could see his phantom arm moving. This was actually a mirror image of his good arm moving. If a patient sends motor commands to both arms to make mirror symmetric movements, he can see his phantom arm moving as well as his good arm. His brain receives confirming visual feedback that his phantom hand is moving correctly in response to his command. The patient said, "My left arm is plugged in again." (ibid, p. 47) Four weeks later, his phantom arm was gone and his pain vanished. It was the first example in medical history of a successful amputation of a phantom limb. (ibid, p. 49)
Ramachandran also tries to explain relation seeing and doing by analyzing "blindsight". There was a patient who became blind by brain damage, but she could identify objects by hearing and touching. Surprisingly, she could also take a letter from a doctor and move it toward the slot of a post, even though she could not tell him whether it was vertical or horizontal. She carried out this behavior without any conscious awareness. (ibid, pp. 63-65) It seemed as though inside her there were another being (a zombie) who moved her body while she was unaware.
Human being has two different visual pathways in the brain. The older pathway goes from the eye straight down to the superior colliculus (上丘) in the brain stem, and from there it eventually gets to higher cortical area especially in the parietal lobes. The newer pathway travels from the eye to the lateral geniculate nucleus (外側膝状核), which is a relay station en route to the primary visual cortex. The pathway from the primary visual cortex leads to both the "how" pathway (the dorsal pathway背側経路) in the parietal lobe and the "what" pathway (the ventral pathway腹側経路)in the temporal lobe (側頭葉).
The older pathway has been preserved as a sort of early warning system for "orienting behavior", a primitive reflex. Damage to the newer pathway leads to blindness in the conventional sense. (ibid, p. 73) Ramachandran supposes that the blindsight patient can use the older pathway to carry out her behavior without conscious awareness that needs the new pathways.
Next, he shows Charles Bonnet syndrome that causes vivid and uncontrollable hallucinations. A patient became blind in the lower half of his field of vision, and visual hallucinations filled the scotoma (暗点). In a visually normal person a blind spot is "filled in" by irrevocable perceptual completion, while the patient's scotoma is filled in with illusionary images.
With the Charles Bonnet syndrome, the images are based on a sort of "conceptual completion" rather than perceptual completion; the images being "filled in" are coming from memory (top-down). A visually normal person has an Interaction between top-down imaginary and bottom-up sensory signals in perception, and the former can be corrected by the latter. (ibid, p. 111)
Ramachandran suggests that we are hallucinating all the time and what we call perception is arrived at by simply determining which hallucination best conforms to the current sensory input. (ibid, p. 112) But if, as happens with the Charles Bonnet syndrome, the brain does not receive confirming visual stimuli, it is free to make up simply its own reality.
Next, Ramachandran examines anosognosia, the state of being unaware of illness. A patient, after a stroke that damaged the right hemisphere, was paralyzed on the left side of her body. She seemed blissfully indifferent to her predicament ---apparently unaware of the fact. Not only was she unaware but also denied that her left hand was paralyzed. She said she could clap with her both hands. (Actually she moved her right hand only.) Another patient had also somatoparaphrenia, the denial of ownership of one's own body parts. He not only denied that his arm was paralyzed but asserted that the arm lying in the bed next to him didn't belong to him. He said, "It's my brother's arm." (ibid, p. 131)
When Ramachandran irrigated ice-cold water into a denial patient's left ear canal, she began to admit that she had had no use of her left arm for a few weeks. This affirmation implies that even though she had been denying her paralysis, the memories of her paralyzed limb had been registering somewhere in her brain, yet access to them had been blocked. The cold water acted as a truth serum (血清)that brought her repressed memories about her paralysis to the surface. But twelve hours later, she denied it again. She didn't remember what she had said, and replied that she had said that her arm had not been paralyzed. Indeed, it was almost as if there were two separate conscious human beings who were mutually amnesic. (ibid, pp. 145-146)
Ramachandran explains this self-defense by the different functions between the left hemisphere and the right hemisphere. The left hemisphere's job is to create a belief system or model and to fold new experiences into that belief system. If confronted with some new information that doesn't fit the model, it relies on Freudian defense mechanisms to deny, repress, or confabulate.
The right hemisphere's strategy is to play Devil's Advocate, to question the status quo and look for global inconsistencies. When anomalous information reaches a certain threshold, the right hemisphere decides that it is time to force a complete revision of the entire model and start from scratch.
If the right hemisphere is damaged, the left hemisphere is then given free rein to pursue its denial, confabulations and other strategies. (ibid, p. 136) A denial patient cannot revise her model of reality because her right hemisphere, with its mechanisms for detecting discrepancies, is out of order. To respond incompatible anomalies, creating multiple personalities, balkanization is better than civil war for the left hemisphere. Even normal persons have such experiences. (ibid, p. 147)
Next, Ramachandran examines Capgras' delusion. A patient said about his parents, "They look exactly like my parents but they really aren't. They are imposters."(ibid, p. 159)
Ramachandran suggests that his strange behavior might have resulted from a disconnection between the two areas in the brain (one concerned with recognition and the other with emotions). Patient's face recognition pathway was still completely normal, but the connections between this face region and his amygdale (扁桃核) had been selectively damaged. He could not experience any emotions, familiarity when looking at parents' faces, so he thought they were not real parents.
The patient sometimes duplicated himself. When shown his picture, he replied, "This is another Arthur (patient's name). He looks like me but it isn't me." (ibid, p. 172) He may have a strange belief that the reason he doesn't experience warmth must be because he is not the real Arthur. He asked his mother not to forsake him if the real Arthur returned. (ibid)
Ramachandran says, "Philosophers have argued for centuries that if there is any one thing about our existence that is completely beyond question, it is the simple fact that ‘I’ exist as a single human being who endures in space and time. But even this basic axiomatic foundation of human existence is called into question by Arthur." (ibid, p. 173)
Next, Ramachandran examines whether human brain has a module for religion. With a transcarnial magnetic stimulator, a Canadian psychologist, Michael Persinger, stimulated parts of his temporal lobes. He experienced God for the first time in his life.
Patients with epileptic (癲癇)seizures originating in the left temporal lobe can have intense, spiritual experiences during the seizures and sometimes become preoccupied with religious and moral issues even during the seizures-free periods.
Ramachandran questions, "If religious beliefs are merely the combined result of wishful thinking and a longing for immortality, how do you explain the flight of intense religious ecstasy experienced by patients or their claim that God speaks directly to them?" (ibid, p. 176)
After examining some possible interpretations, Ramachandran says, "There are circuits in the human brain that are involved in religious experience and these become hyperactive in some epileptics. We still don't know whether these circuits evolved specially for religion or whether they generate other emotions that are merely conductive to such beliefs. “(ibid, p. 188)
Finally, he examines the consciousness and the self. Consciousness arises not from the whole brain but rather from certain specialized brain circuits that carry out a particular style of computation. The circuitry that embodies the vivid subjective quality of consciousness resides mainly in parts of the temporal lobes (such as the amygdala, septum中隔, hypothalamus視床下部, and insular cortex島部皮質) and a single projection zone in the frontal lobes前頭葉---the cingulate gyrus帯状回. (ibid, p. 228)
Ramachandran asks why natural selection created not brains working without consciousness, but ones with consciousness. Philosophers call the vivid subjective quality of consciousness “qualia”. Ramachandran examines the qualia-laden perception.
First, the qualia-laden perception is irrevocable by higher brain centers. Second, qualia-laden perception affords the luxury of choice or associates other related concepts or images. These two functional features of qualia, irrevocability on the input side and flexibility on the output side, make it possible to make decisions. But to make decisions on the basis of a qualia-laden representation, the representation needs to exist long enough for us to work with it.
So third, qualia-laden perception has short-term memory. Qualia are irrevocable in order to eliminate hesitation and to confer certainty to decisions. (ibid, p. 242) Therefore the qualia-laden perception is different from thinking, believing, and imagination.
Brains with consciousness might be of advantage for the animals to have various options and make decisions to cope with different conditions.
Ramachandran states, “We believe that the self---the ‘I' inside us---actually experiences these qualia. Qualia and self are really two sides of the same coin; obviously there are no such things as free-floating qualia not experienced by anyone." (ibid, p. 246)
Theses above mentioned patients show that our consciousness and its disorders have its base in the brain. Although Ramachandran discusses explicitly philosophical reductive physicalism, he says, "In this revolution of brain science, we have given up the old idea that there is a soul separate from our minds and bodies. Far from being terrifying, the new idea is very liberating. If you think you are something special in this world, engaging in a lofty inspection of the cosmos from a unique vantage point, your annihilation becomes unacceptable. But if you are really part of the great cosmic dance of Shiva, rather than a mere spectator, then your inevitable death should be seen as a joyous reunion with nature rather than as a tragedy." (ibid, p. 157)
Here he insists that death is reunion with nature, but I wonder in what point it is reunion. He suggests that a dead body returns to soil and dust and nothing else remains. He also says, "As I was born in India and raised in the Hindu tradition, I was taught that the concept of the self, the ‘I’ within me is an illusion, a veil called ‘maya’ and I am really one with the cosmos. Ironically, after extensive training in Western medicine and research on neurological patients and visual illusions, I have come to realize that there is much truth in this view---that the notion of a single unified self ‘inhabiting’ the brain may indeed be an illusion." (ibid, p. 227)
He seems to insist that the brain creates consciousness and the self, but it is actually an illusion. This sounds like an argument for eliminative reductive physicalism, but in Ramachandran, it is harmonized with metaphysical Hindu tradition.