The Master and His Emissary
The Master and His Emissary
Bibliography
- Author: Iain McGilchrist
- Full_Title: The Master and His Emissary
- Category: books
- Document Tags: [ neuroscience, science, ]
- Last Highlighted Date: 2024-11-16 18:19:37.710225+00:00
Highlights
- The whole problem is that we are obsessed, because of what I argue is our affiliation to left-hemisphere modes of thought, with ‘what’ the brain does – after all, isn’t the brain a machine, and like any machine, the value of it lies in what it does? I happen to think this machine model gets us only some of the way; and like a train that drops one in the middle of the night far from one’s destination, a train of thought that gets one only some of the way is a liability. The difference, I shall argue, is not in the ‘what’, but in the ‘how’ – by which I don’t mean ‘the means by which’ (machine model again), but ‘the manner in which’, something no one ever asked of a machine. I am not interested purely in ‘functions’ but in ways of being, something only living things can have.
- However one conceives the relationship of mind and brain – and especially if one believes them to be identical – the structure of the brain is likely to tell us something we otherwise could not so easily see. We can inspect the brain only ‘from the outside’ (even when we are probing its innermost reaches), it is true: but we can inspect the mind only ‘from within’ (even when we seem to objectify it). Seeing the brain’s structure is just easier. And since structure and function are closely related, that will tell us something about the nature of our mental experience, our experience of the world. Hence I believe it does matter. But I should emphasise that, although I begin by looking at brain structure in relation to the neuropsychological functions that we know are associated with each hemisphere, my aim is purely to illuminate aspects of our experience.
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- Note: See Integrated Information Theory for explanation of how brain structure relates to consciousness and experience.
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- The brain has evolved, like the body in which it sits, and is in the process of evolving. But the evolution of the brain is different from the evolution of the body. In the brain, unlike in most other human organs, later developments do not so much replace earlier ones as add to, and build on top of, them.
- In other words, the structure of the brain reflects its history: as an evolving dynamic system, in which one part evolves out of, and in response to, another.
- If it is true that consciousness arises from, or at any rate is mediated by, the sheer density and complexity of neuronal interconnections within the brain, this structure has some important consequences for the nature of that consciousness. The brain should not be thought of as an indiscriminate mass of neurones: the structure of that mass matters. In particular it has to be relevant that at the highest level of organisation the brain, whether mediator or originator of consciousness, is divided in two.
- Both hemispheres are involved in almost all mental processes, and certainly in all mental states: information is constantly conveyed between the hemispheres, and may be transmitted in either direction several times a second. What activity shows up on a scan is a function of where the threshold is set: if the threshold were set low enough, one would see activity just about everywhere in the brain all the time. But, at the level of experience, the world we know is synthesised from the work of the two cerebral hemispheres, each hemisphere having its own way of understanding the world – its own ‘take’ on it.
- Descartes was a great dualist. He thought not only that there were two types of substance, mind and matter, but that there were two types of thinking, two types of bodily movement, even two types of loving; and, sure enough, he believed there were two types of people: ‘the world is largely composed of two types of minds …’
- But the evidence is that the primary effect of callosal transmission is to produce functional inhibition.5 So much is this the case that a number of neuroscientists have proposed that the whole point of the corpus callosum is to allow one hemisphere to inhibit the other.
- And, in the ultimate case of the modern human brain, its twin hemispheres have been characterised as two autonomous systems.11
- But the fundamental problem in explaining the experience of consciousness is that there is nothing else remotely like it to compare it with: it is itself the ground of all experience. There is nothing else which has the ‘inwardness’ that consciousness has.
- Mind has the characteristics of a process more than of a thing; a becoming, a way of being, more than an entity.
- It has been accepted since the days of the great anatomist John Hunter that structure is at some level an expression of function
- There is a need to focus attention narrowly and with precision, as a bird, for example, needs to focus on a grain of corn that it must eat, in order to pick it out from, say, the pieces of grit on which it lies. At the same time there is a need for open attention, as wide as possible, to guard against a possible predator.
- In humans, just as in animals and birds, it turns out that each hemisphere attends to the world in a different way – and the ways are consistent. The right hemisphere underwrites breadth and flexibility of attention, where the left hemisphere brings to bear focussed attention.
- Through the direction and nature of our attention, we prove ourselves to be partners in creation, both of the world and of ourselves.
- If it turns out that the hemispheres have different ways of construing the world, this is not just an interesting fact about an efficient information-processing system; it tells us something about the nature of reality, about the nature of our experience of the world, and needs to be allowed to qualify our understanding of the brain as well.
- The first thing to make clear is that, although the brain is often described as if it were composed of bits – ‘modules’ – of one kind or another, which have then to be strung together, it is in fact a single, integrated, highly dynamic system. Events anywhere in the brain are connected to, and potentially have consequences for, other regions, which may respond to, propagate, enhance or develop that initial event, or alternatively redress it in some way, inhibit it, or strive to re-establish equilibrium. There are no bits, only networks, an almost infinite array of pathways.
- We have to be able to recognise (‘re-cognise’) what we experience: to say this is a ‘such-and-such’, that is, it has certain qualities that enable me to place it in a category of things that I have experienced before and about which I have certain beliefs and feelings. This processing eventually becomes so automatic that we do not so much experience the world as experience our representation of the world. The world is no longer ‘present’ to us, but ‘re-presented’, a virtual world, a copy that exists in conceptual form in the mind.
- The conventional neuropsychological literature distinguishes five types of attention: vigilance, sustained attention, alertness, focussed attention and divided attention. While not identical, vigilance and sustained attention are similar, and they are often treated as one concept. Together with alertness, they form the basis of what has been called the intensity axis of attention. The other axis is selectivity, made up of the two remaining types, focussed and divided attention.
- More specifically there is evidence of left-hemisphere dominance for local, narrowly focussed attention and right-hemisphere dominance for broad, global, and flexible attention.