Recognising parts of the body that make up the mind

In 1995, Michael Gazzaniga edited, and MIT Press published, The Cognitive Neurosciences , a 1,447-page reference volume containing long articles by eminent researchers covering most aspects of the cognitive neurosciences. The volume was highly successful and received near-universal praise. One reviewer (R. A. Drake) wrote: "This may be the most important reference book in cognitive neuroscience for the next decade." Presumably Drake's qualification "for the next decade" was based on the pace of development within the field. If so, Drake appears to have underestimated, for just five years down the line, we have what is described as the second edition of Gazzaniga's outstanding reference work.

In truth, the second edition shares little with its predecessor other than the highly effective formula expertly applied by Gazzaniga and his sub-editors. Most chapters are entirely new, and those that remain from the 1995 edition are substantially rewritten. This second edition supplements, rather than supersedes, the first. We should perhaps expect no less. Cognitive neuroscience was in its infancy in 1995, and advances in methods have led to corresponding advances in our understanding of how the brain and mind function. There is no reason to expect progress to slow, and we might anticipate a third edition sometime in 2005.

The structure of The New Cognitive Neurosciences mirrors that of its predecessor. It grew out of an intensive 18-day workshop, which ensured consistency and integration between the 181 contributors. The volume consists of 11 sections and 94 chapters spanning almost every area of the cognitive neurosciences, and it is capped with a highly comprehensive and very usable 50-page index. There are sections on development, neural plasticity, sensory systems, motor systems, attention, memory, language, higher cognitive functions, emotion, evolution and consciousness. Each is prefixed by an introduction by the section editor (only one of whom is new to the second edition), which typically outlines the major changes in the area since the publication of the first edition and which attempts to stress the main themes represented in the following chapters. All this makes for a hugely impressive volume. Such breadth, coupled with the standard of chapters, makes for a breathtaking achievement.

The chapters are a mix of high-quality review articles and more speculative research papers in which a novel perspective or theory is presented. Most chapters are written by leading figures in the area, and all are aimed at the general cognitive neuroscience community. They are accessible, with no highly technical articles laden with specialist jargon - though, if needed, pointers to such articles are given.

Integration across chapters and within each section is good, with a range of methods, theories and issues reviewed in each section. The volume serves as an excellent introduction to all areas of cognitive neuroscience and allows specialists in one area quickly and easily to obtain a broad overview of the key issues and debates in other areas. As such, The New Cognitive Neurosciences will be of interest both to experienced researchers and to new students of the brain and cognitive sciences. It may also serve an important sociological role: to further integrate the theories and methods developed and employed by researchers across the component disciplines of cognitive neuroscience. The volume also underscores the continuing commitment and support of MIT Press for the cognitive and brain sciences - a commitment evident in a number of major projects, including The New Cognitive Neurosciences , MIT's Encyclopaedia of the Cognitive Sciences and the Cognet website.

One of the key factors in the development of cognitive neuroscience as a distinct scientific enterprise is the twin realisations of the inadequacies of the methods employed by the component disciplines in establishing a complete picture of the workings of brain and mind, and of the complementary nature of those methods. The methods of neurophysiology, such as single-cell recordings, might be adequate for mapping the functioning of neurons and the general functional role of neural areas, but they can provide at best limited illumination of the information-processing activities involved in higher mental processes.

Similarly, controlled psychophysical experiments might allow the development of theories of perceptual and attentive processes, but those theories must respect the basic neurophysiological structure of the perceptual systems, and the outputs of their component processes must be in principle computable by the neural architecture. Thus, only by adopting multiple methods derived from a range of disciplines can any single aspect of brain functioning be understood at all levels.

The methods that characterise the various cognitive neurosciences are prominent in all chapters, and although neuro-imaging and related methods for mapping neural activity feature strongly in most chapters, a range of other methods - such as single-cell recording, controlled experimentation, case studies of impaired individuals and computational modelling - are also employed in most sections. Even the chapters in those sections that are likely to be most controversial, those on evolution and consciousness, generally eschew philosophy and opinion in favour of more objective scientific method.

Nevertheless, the introduction to the evolution section, by Leda Cosmides and John Tooby, reads uncomfortably. The authors seek to justify the role of evolutionary constraints in cognitive neuroscience. While the development of some aspects of brain function are surely a product of evolutionary pressures, it is perhaps odd that evolution is treated in its own section, as if one can take it or leave it, rather than integrated into other sections. One might imagine the evolutionary perspective's being integrated into chapters in the sections on sensory systems, motor systems and/or higher cognitive functioning. As it happens, most evolution chapters are oriented towards aspects of higher cognitive functioning. These are precisely the areas where evolution theory is at its most controversial.

In contrast, no discomfort is evident in the section on consciousness. Consciousness has been established, despite the odds, as a respectable area of scientific study, even if there is dispute within the area about precisely what consciousness is or what aspects of it are important, interesting or even amenable to scientific study. Half of this section is conservative, in the questions addressed and in the approaches employed. The implications of now-standard neuropsychological findings (relating to blindsight and split-brain patients) for theories of consciousness are discussed, and neural activation during the process of routinising a cognitive skill is charted.

Other chapters concern the role of the prefrontal cortex in the representation of time, the search for a hypothesised neural correlate of consciousness, and apparent changes in conscious experience during sleep. These chapters are of considerable interest, but by their nature they are more speculative. The section as a whole illustrates the mix present throughout the volume between review articles and current research.

Another section that deserves a mention is that on emotion. The full range of cognitive neuroscientific methods is being applied to questions concerning the origins and neural correlates of emotional states and their effects upon cognitive processing. An emotion section was present in the previous edition, but the literature on which it was based was limited. Much has since been learnt about emotional states, the processing of emotive stimuli and the role of the brain structures such as the amygdala in emotional processes. Nevertheless, Joseph LeDoux, the section editor, cautions the reader. Most work on the cognitive neuroscience of emotion concerns just one emotion - fear. Relatively little is known about other emotions. Indeed, there is no simple catalogue of emotions.

The eight other sections have fewer expectations to live up to. While controversies abound in all areas, the questions and issues are at least more clearcut. Thus, in the fields of development and recovery from brain injury, one may query the extent or limits of neural plasticity and how that plasticity is manifest at the molecular, cellular-systems and cognitive levels.

Similarly in the field of attention, one may query the extent to which unattended information is processed or the role of specific neural structures in attentional processes, and in the field of motor control, the neural mechanisms and computational principles that determine the path through space of a hand (attached to a limb with multiple degrees of freedom) when reaching for an object. These questions are well formed, and the range of methods being applied by cognitive neuroscientists is beginning to provide answers to each of them.

Despite some reservations, there are few real criticisms that one can make of The New Cognitive Neurosciences . One can look for omissions, and arguably many people would feel that some area is under-represented.I feel that the section on higher cognitive functions is a little sparse and that planning and problem-solving have been sacrificed at the expense of imagery and categorisation - but in a quickly growing field with an already-vast literature, such feelings are inevitable.

Perhaps a more justifiable criticism is that it is sometimes difficult to see solid integration between the component disciplines. Some chapters are predominantly neuroscience, others are predominantly cognitive psychology. On rare occasions, there appear to be gulfs between the perspectives adopted in different chapters within a section. This point is made explicit in Pasko Rackic's introduction to the section on development, in which he makes a plea for more scientists to work on the links between traditional levels. More seriously, there is little cross-talk, and there are clear gulfs between sections.

It would be wrong, however, to argue that cognitive neuroscience therefore represents a field that has subsumed its component disciplines and methods without integrating them. Cognitive neuroscience is young and vigorous. This volume and the workshop that gave birth to it are vital for establishing the integration between the component disciplines of cognitive neuroscience that is necessary if real progress is to be made in understanding the brain, the mind and the relation between them.

Richard Cooper is lecturer in psychology, Birkbeck College, University of London.