Cerebral cartography

Susan Greenfield provides an interesting general introduction to the discipline of neuroscience that is clearly aimed at the interested lay reader. Books of this kind are notoriously difficult to write, as the main requirement is that they explain difficult concepts simply. But simplification can irritate the cognoscenti. Greenfield's book is remarkably free of offence in this regard, though not entirely so.

The book is strongest in the domain of pharmacology, especially the understanding of brain function. It is particularly rewarding to find eloquently written expository sections dealing with the physicality of brain function, as it is crucial to point out to a lay audience that these are the physical principles to which cognitive theories of memory, language, consciousness, etc, must ultimately be reconciled.

Books of this sort afford authors the opportunity to publish what they really think, as opposed to what editors and referees will allow them to get away with. Greenfield takes full advantage of this liberty to speculate upon the nature of consciousness and the difficulties of reconciling "bottom-up", cellular accounts of brain function with "top-down", cognitive accounts. The author also uses her book to mount a violent attack on computer modelling of the brain. However, in her critique of this approach she leaves herself open to legitimate criticism. For example, she doubts that computers could ever be given "common-sense", but then provides no explanation of what commonsense is. Computational modellers may well feel justified in asking that she define this function in human cognition before asking that they seek to do so in computers.

Proponents of computer modelling will also gleefully seize upon her point that brains and computers are very different physically. This is indisputably true, but then many workers in the field of computational modelling have never claimed otherwise and have merely pointed out that as nature has been able to instantiate cognition on a physical system then so, too, might we.

Wide-ranging books such as this challenge the author to stay on top of developments in other fields and occasionally she betrays her lack of familiarity with recent developments. For example, in her discussion of synaesthesia no distinction is made between naturally occurring synaesthesia and the forms found in schizophrenia, traumatic brain injury and as the result of drug use, in spite of well documented differences in the complexity and probable aetiology of these diverse forms. Thus Greenfield's dismissal of any one explanation of synaesthesia seems injudicious.

It is also disappointing to read that she feels that any real explanation of synaesthesia is impossible due to its status as "a facet of consciousness". The use of brain imaging techniques and recent theories of preserved neural connectivity have already illuminated our understanding of the neural correlates of coloured hearing and so it seems a little early in the game to preclude an explanation couched in terms that do not involve consciousness.

Ultimately books of this kind should be judged on whether they manage to fascinate and intrigue those new to the neurosciences. By this criterion, I suspect Greenfield has succeeded.

John E. Harrison is senior neuropsychologist, CeNeS Ltd, St John's Innovation Centre, Cambridge.