Second, given my earlier remarks about the self, the notion of the self as being defined by a set of attributes - embodiment, agency, unity, continuity - maybe we will succeed in explaining each of these attributes individually in terms of what's going on in the brain. Then the problem of what is the self will vanish or recede into the background.
Third, maybe the solution to the problem of the self won't be a straightforward empirical one. It may instead require a radical shift in perspective, the sort of thing that Einstein did when he rejected the assumption that things can move at arbitrarily high velocities. When we finally achieve such a shift in perspective, we may be in for a big surprise and find that the answer was staring at us all along. I don't want to sound like a New Age guru, but there are curious parallels between this idea and the Hindu philosophical view that there is no essential difference between self and others or that the self is an illusion.
Now I have no clue what the solution to the problem of self is, what the shift in perspective might be. If I did I would dash off a paper to Nature today, and overnight I'd be the most famous scientist alive. But just for fun let me have a crack at it, at what the solution might look like.
Our brains were essentially model-making machines. We need to construct useful, virtual reality simulations of the world that we can act on. Within the simulation, we need also to construct models of other people's minds because we're intensely social creatures, us primates. We need to do this so we can predict their behaviour. We are, after all, the Machiavellian primate. For example, you want to know was what he did a wilful action. In that case he might repeat it. Or was it involuntary in which case it's quite benign. Indeed evolution may have given us the skill even before self-awareness emerged in the brain. But then once this mechanism is in place, you can also apply it to the particular creature who happens to occupy this particular body, called Ramachandran.
At a very rudimentary level this is what happens each time a new-born baby mimics your behaviour. Stick your tongue out next time you see a new-born-baby and the baby will stick its tongue out, mimicking your behaviour, instantly dissolving the boundary, the arbitrary barrier between self and others. And we even know that this is carried out by a specific group of neurons in the brain, in your frontal lobes, called the mirror neurons. The bonus from this might be self-awareness.
With this I'd like to conclude this whole series of lectures. As I said in my first lecture, my goal was not to give you a complete survey of our knowledge of the brain. That would take fifty hours, not five. But I hope I've succeeded in conveying to you the sense of excitement that my colleagues and I experience each time we try to tackle one of these problems, whether you're talking about hysteria, phantom limbs, free will, the meaning of art, denial, or neglect or any one of these syndromes which we talked about in earlier lectures. Second, I hope I've convinced you that by studying these strange cases and asking the right questions, we neuroscientists can begin to answer some of those lofty questions that thinking people have been preoccupied with since the dawn of history. What is free will? What is body image? What is the self? Who am I? - questions that until recently were the province of philosophy.
No enterprise is more vital for the wellbeing and survival of the human race. This is just as true now as it was in the past. Remember that politics, colonialism, imperialism and war also originate in the human brain.
Thank you.
We would like to thank the Society for Neuroscience for their premission to reproduce this glossary. Some ammendations have been made.
A
Acetylcholine: A neurotransmitter in both the brain, where it may help regulate memory, and in the peripheral nervous system, where it controls the actions of skeletal and smooth muscle.
Action Potentiaclass="underline" This occurs when a neuron is activated and temporarily reverses the electrical state of its interior membrane from negative to positive. This electrical charge travels along the axon to the neuron's terminal where it triggers or inhibits the release of a neurotransmitter and then disappears.
Adrenal Cortex: An endocrine organ that secretes corticosteroids for metabolic functions: aldosterone for sodium retention in the kidneys, androgens for male sexual development, and estrogens for female sexual development.
Adrenal Medulla: An endocrine organ that secretes epinephrine and norepinephrine for the activation of the sympathetic nervous system.
Affective Psychosis: A psychiatric disease relating to mood states. It is generally characterized by depression unrelated to events in the life of the patient, which alternates with periods of normal mood or with periods of excessive, inappropriate euphoria and mania.
Agonist: A neurotransmitter, a drug or other molecule that stimulates receptors to produce a desired reaction.
Amino Acid Transmitters: The most prevalent neurotransmitters in the brain, these include glutamate and aspartate, which have excitatory actions, and glycine and gamma-amino butyric acid (GABA) which have inhibitory actions.
Amygdala: A structure in the forebrain that is an important component of the limbic system.
Androgens: Sex steroid hormones, including testosterone, found in higher levels in males than females. They are responsible for male sexual maturation.
Anosognosia: A syndrome in which a person with a paralysed limb claims it is still functioning. One of Professor Ramachandran's patients, who had suffered a stroke which had paralysed the left side of her body, refused to accept that her arm couldn't move. Even though lucid in every other aspect (including awareness of the fact that she had suffered a stroke) she claimed her left arm was carrying out tasks even though clearly it wasn't. Anosognosia means denial of illness. An explanation may involve close analysis of the different roles of the left and right hemispheres of the brain.
Antagonist: A drug or other molecule that blocks receptors. Antagonists inhibit the effects of agonists.
Aphasia: Disturbance in language comprehension or production, often as a result of a stroke.
Auditory Nerve: A bundle of nerve fibers extending from the cochlea of the ear to the brain, which contains two branches: the cochlear nerve that transmits sound information and the vestibular nerve that relays information related to balance.
Autonomic Nervous System: A part of the peripheral nervous system responsible for regulating the activity of internal organs. It includes the sympathetic and parasympathetic nervous systems.
Axon: The fiberlike extension of a neuron by which the cell sends information to target cells.
B
Basal Ganglia: Clusters of neurons, which include the caudate nucleus, putamen, globus pallidus and substantia nigra, that are located deep in the brain and play an important role in movement. Cell death in the substantia nigra contributes to Parkinsonian signs.
Blindsight: Some patients who are effectively blind because of brain damage can carry out tasks which appear to be impossible unless they can see the objects. For instance they can reach out and grasp an object, accurately describe whether a stick is vertical or horizontal, or post a letter through a narrow slot . The explanation appears to be that visual information travels along two pathways in the brain. If only one is damaged, a patient may lose the ability to see an object but still be aware of its location and orientation.