Brain, Vol. 123, No. 1, 187-189,
January 2000
© 2000 Oxford University Press
Book reviews |
CONSCIOUSNESS IN ACTION.
.
Department of Clinical Neurosciences, University of Edinburgh, Edinburgh, UK
The study of consciousness is an increasingly popular pastime, if not yet an entirely respectable one. Several factors have contributed to its growing appeal over the last 10 years. First, basic neuroscience, allied with functional imaging, has revealed exquisite correlations between neural activity and subjective experience. These lend powerful support to the neuroscientist's article of faith, that every distinction drawn in awareness will be reflected in a distinctive pattern of neural activity. Second, there is a growing understanding of a range of neural processes which influence behaviour, yet never seem to be captured by the `spotlight' of consciousness, such as blindsight, `blind touch' and `blind smell'. Subtracting the activity which subserves these unconscious abilities from the totality of the neural processes excited by sensation should help to delineate the neurology of consciousness. Finally, the wider intellectual community, and especially its philosophers, are excited by the prospect of healing the ancient rift between body and mind. As mental activity is ever more persuasively located in the nooks and crannies of the brain, and the barriers between psychiatry and neurology begin to melt away, our Cartesian assumptions serve us less and less well—yet how are we to replace them?
Despite its title, consciousness is not really the main preoccupation of the engaging collection of essays edited by Steven Rose. These were garnered from talks given at a 2 day symposium at the British Association for the Advancement of Science, and the core of the book is an entertaining miscellany of reviews on topics in cognitive neuroscience and neuropsychiatry. The taxonomy and neurophysiology of memory, the pharmacology of emotion, the genesis of Alzheimer's disease and the validity of the concept of schizophrenia are lucidly and succinctly discussed by a well-chosen panel of—predominantly British—authors.
Later chapters home in on awareness. Penrose and Aleksander debate the merits of computational theories of mental activity; Wolf Singer reviews the potential for neuronal synchronization to `bind' the contents of consciousness; Susan Greenfield proposes that neuronal assemblies are the neural correlates of consciousness, and examines the match between their properties and those of subjective experience. It is a shame that some of the speakers at the symposium were unable to contribute to the book: Semir Zeki's thoughts on the basis of conscious vision would have been especially welcome here.
By and large these authors avoid what has recently been termed the `hard' problem of consciousness. They explore the neural correlates of experience without worrying overmuch about why neural activity of these particular kinds should generate experience—how, to quote the philosopher Colin McGinn, `the water of the physical brain is turned into the wine of consciousness'. But several of the contributors acknowledge the problem and some reach towards a solution. Rose himself argues that we tend to look for it in the wrong place: consciousness will perplex us until we realize that it is `fundamentally a social phenomenon, not the property of an individual brain or mind'. Wolf Singer broadly concurs, tracking our puzzlement back to the `theory of mind' which we develop through our early—and forgotten—social interactions. Richard Gregory and Roger Penrose, by contrast, hint that the phenomena of consciousness indicate deep inadequacies in contemporary science.
Questions of this order are the point of departure for Susan Hurley's painstaking but difficult essays. How should we understand the relationship between the events which pass through our minds, their `subpersonal' vehicles within our brains, and the wider environment in which both occur? How are perception and willed action, the two great activities of mind, related to each other? Does the answer tell us anything important about the broad nature of mental events? What grounds the unity of personal consciousness? Hurley's discussion of each of these issues tends to imply that the mind–body problem is more in need of a diagnosis than of a solution: somehow our thinking on the subject has lost its way, and only meticulous logic can bring us safely home.
Her book's punning title points toward the book's central thread of arguement. We tend to regard perception as input from the world to the mind, action as output from mind to world: this picture vividly implies the separateness of mind from world. Yet perception and action are interdependent in such a rich variety of ways that the simple Cartesian model is, at best, open to question. If the picture is misleading, and both perception and action emerge from distributed interactive processes through the brain, then mind can be relocated, `embodied and embedded in the world'.
This argument captures one important source of the excitement in current neuropsychology. Until quite recently, functional maps of the cerebrum sketched in the sensory cortices, motor maps, and then a vast terra incognita, `association cortex', a suitably elusive location for the activities of the mind. But times have changed. The discovery that the visual cortex contains multiple, functionally specialized but highly interactive, maps of the visual world, is transforming our view of the process by which sensation yields knowledge and guides action. As the functional geography of `association cortex' begins to emerge from the haze, the classification of areas into `sensory' or `motor' territories looks increasingly artificial: is the amygdala, which integrates the perception, experience and enactment of fear a sensory or a motor nucleus? Are `mirror' cells in premotor cortex, which are excited both by performing a movement and by watching someone else make the same movement, involved in action or perception? Learning more of the functions and interactions of areas like these paves the way for the relocation of mind in world.
Given its mainly philosophical aims, this book pays unusually close attention to data from neuroscience. When Hurley leaves the evidence behind, her analysis of mental concepts is always interesting, but I was sometimes left unsure of the grounds for her conclusions. For example, in a lucid discussion of ways in which consciousness might presuppose self-consciousness, she argues that `perspective' and `access', both forms of `non-conceptual self-consciousness', are presupposed. Perspective is the ability to `keep track of the relations between what creatures do and what they perceive'; access is the ability to form and act on intentions whose content is provided by information creatures are conscious of. These are certainly crucial abilities which we, and plausibly other conscious agents, normally possess. But are they logically or empirically required for every variety of consciousness? Is the idea of experience in a subject who is deprived of the ability to `form or act on intentions' incoherent? Certainly not to all contemporary philosophers of mind: David Chalmer's evocation of `an unarticulated flash of experience' is not obviously nonsensical, but would this form of consciousness allow either perspective or access?
Hurley's essays have the ring of work in progress, as she chisels away at the concepts which baffle our thinking about our brains and the minds they give rise to. The essays overlap, and assume a fair degree of philosophical sophistication in the reader. But while we are edging towards solutions to the deeper problems which lie in the sights of these volumes, help from the logician will be sorely needed in the laboratory. Both these thoughtful books deserve their place on its shelves.
Notes
By S. L. Hurley. 1998. Pp. 506. London: Harvard University Press. Price £34.50. ISBN 0-674-16420-2.
FROM BRAINS TO CONSCIOUSNESS. Edited by Steven Rose. 1998. Pp. 278. Princeton: Princeton University Press. Price $29.95. ISBN 0-691-00469-2.
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