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.Third, these conscious contents are experienced by the same ‘me’.In other words, there is a single experiencer as well as the stream of experiences.A successful science of consciousness must therefore explain the contents of consciousness, the continuity of consciousness, and the self who is conscious, and it must do so starting with a multiply parallel and non-centralized brain.We shall return to the question of self, but for now let’s begin with the apparently innocent idea that there are contents of consciousness.The important point here is that most of what goes on in the human brain seems to be outside of consciousness and even inaccessible to consciousness.We see the trees blowing in the wind, but we are not conscious of all the rapid electrical activity in the visual cortex that leads up to that perception.We sit at our computer consciously replying to an email, but are unconscious of how our hands type the words or where the words are coming from.We consciously struggle to win that game of table tennis, oblivious to the fast visuo-motor control that makes our winning shots possible.In all these cases every one of our brain’s cells, with their billions of connections, are active – some firing faster and some slower, depending on what we are doing.Yet most of this activity never makes it into the stream of consciousness or the theatre of my mind.So we call it unconscious or subconscious, or we relegate it to the fringe of consciousness.But what does this really mean? The problem is that this distinction implies a magic difference between the conscious bits and the unconscious bits.Is the conscious brain activity controlled by a supernatural soul or non-physical self, as a dualist might believe? Is there a special place in the brain where consciousness happens? Are there special types of ‘consciousness neuron’ that produce conscious experiences while all the rest do not? Are there certain ways of connecting up neurons that produce consciousness? Or what? As we shall see, there are theories of consciousness corresponding to all these possibilities, but all of them face severe difficulties.In the end, the question seems to be this – do we struggle on with the familiar view of consciousness as a theatre or stream of experiences and try to make it work, or do we throw out all our familiar ways of thinking and begin again? It is worth bearing this question in mind as we consider some of the fascinating research that links consciousness to brain function.SynaesthesiaSome people hear shapes, see noises, or feel sounds, and this odd form of unified consciousness is surprisingly common.Many young children have synaesthesia but the effects usually disappear with age, leaving something like 1 in 200 adults as synaesthetes.Synaesthesia runs in families, is more common in women and left-handers, and is associated with good memory but poorer maths and spatial ability.It is especially prevalent among poets, writers, and artists.In the most common form of synaesthesia, numbers or letters are always seen as coloured.These experiences cannot be consciously suppressed, and when tested after many years most synaesthetes report that exactly the same shapes or forms or colours are induced by the same stimuli.Many synaesthetes hide their abilities, and for a long time psychologists doubted they were real, but recent research has confirmed the prevalence and stability of the effects.Synaesthetes may have more connections between the different sensory areas of the brain, and Ramachandran argues that since numbers and colour are processed in adjacent areas this might explain the most common form of synaesthesia.The neural correlates of consciousness (NCCs)Everyone has experienced pain.Pain is horrid.It hurts and we don’t like it.But what is it? Pain is a perfect example for considering the neural correlates of consciousness; that is, the brain events that are correlated, or associated, with subjective experiences.On the subjective side, pain is quintessentially a private experience.We cannot describe our pain to anyone else.We cannot know how bad someone else’s pain is, except by watching their behaviour, and even then we might think that they are bluffing, although we can never be sure.We cannot even remember how pain feels once it is gone.Indeed, it is often said that no woman would ever have a second baby if she could remember the pain of the first.In the end, the only way we can really know what pain is like is when we are suffering it now.On the objective side, pain happens when, for example, the body is injured.Various chemical changes take place at the site of the injury and then signals pass along specialized neurons called C-fibres to the spinal cord, and from there to the brain stem, thalamus, somatosensory cortex (which includes a map of all the areas of the body), and cingulate cortex of the brain.Brain scans show that there is a strong correlation between the amount of pain experienced and the amount of activity in these areas.In other words, we understand some of the neural correlates of pain.Now it is important to remember that ‘correlation does not imply a cause’.It is notoriously easy to slip from correlations to false conclusions about causes, as in this simple example.Suppose that Freddie has a habit of going into the living room and turning on the television.Almost every time he does so, his action is soon followed by the Simpsons coming on.When other people go into the living room and press the button, completely different things come on.If correlation implied cause then we would have to conclude that Freddie’s action caused the Simpsons to appear.In this case, of course, we are not fooled.But in many other cases we might be.The rule of thumb to remember is this: Whenever there is a reliable correlation between A and B there are three possible causal explanations: A caused B, B caused A, or A and B were both caused by something else.In addition, it could be that A and B are actually the same thing even though they do not appear to be (like water and H2O, or the morning star and the evening star).Which is the case with pain? Maybe the physical changes cause the pain, in which case we have to solve the hard problem.Maybe the pain causes the physical changes, in which case we need a supernatural theory.Maybe something else causes both, in which case we have no idea what.Or maybe they are really the same thing.Many materialists have argued for this last explanation, but if it is true we have absolutely no idea how it could be true.How could this awful, toe-curling, horrible, unwanted feeling in the side of my head actually be the firing of a few of my C-fibres?This question illustrates the depth of our present ignorance about consciousness, but we should not despair.Science has a habit of solving what seem to be impossible problems and may do so again.So let’s look at an example of some very clever experiments designed to delve into the neural correlates of consciousness – in this case, visual consciousness.5.This ambiguous figure is called a Necker cube.If you keep looking at it for some time, you will find that it flips between two equally possible interpretations, as though the two views are competing for consciousness [ Pobierz całość w formacie PDF ]