The grey areas of grey matter

A fascinating odyssey into research on the brain advises Richard Cooper not to lose his head over outlandish claims

Our knowledge of the brain has increased dramatically over the past decade or two. This knowledge brings with it threats and opportunities - threats over how ethically dubious governments or researchers might use the knowledge to subvert nature or society; and opportunities to develop therapies and treatments for neural damage and dysfunction.

In The 21st-Century Brain , Steven Rose brings together much current research in an attempt to clarify what we know, what we do not know and what we can never know about the brain, and to predict some of the consequences of this knowledge. The result is a view of a brave new world that may await us, and a view of the issues that should concern us now given the direction of current progress.

The 21st-Century Brain is an odyssey through brain evolution and development, through the history of psychotropic drugs and on to the limits of modern drug treatments for disorders such as depression and schizophrenia. A constant theme is the complexity of neural processes and the way that behaviour is the result of numerous interactions spanning multiple time frames. Thus, Rose considers the evolution of behaving systems, from simple single-cell organisms to humans, and the development of brains from embryos through adolescence. The present, Rose argues, can be understood only in the context of the past, and much of the first half of the book consists of an eloquent summary of the past as it relates to the present structure and functioning of the brain.

The second half of The 21st-Century Brain examines some of the advances made possible by our increasing knowledge of the functioning of neural processes and attempts to extrapolate from this to predict what the future might hold. Rose focuses particularly on the understanding and treatment of neural dysfunction. Dysfunction is itself a difficult concept, for it presupposes some ideal of normal function. After questioning this concept, Rose considers the extent to which existing treatments for disorders such as attention deficit hyperactive disorder, depression and schizophrenia have been successful. The assessment is not overly positive.

Rose suggests that the difficulty with drug treatments for such disorders lies in the complex interactions of neural processes and the problem of establishing the root cause of a disorder. To illustrate, a simplistic view might be that clinical depression is a consequence of low concentrations of the neurotransmitter serotonin at critical brain regions. Treating this with drugs such as Prozac, which increase serotonin availability, will be effective only if the neural systems responsible for serotonin production do not respond to the Prozac by decreasing availability further, and if the serotonin system functions independently of other neurotransmitter systems.

Unfortunately, although drugs such as Prozac may be helpful in some cases, neither of these caveats is guaranteed to hold. Similar comments hold for other drugs that alter the balance of neurotransmitter systems.

An alternative approach to the treatment of neural disorders, particularly degenerative diseases such as Alzheimer's and Parkinson's, is promised by stem-cell research. The promise is that stem cells, once introduced to degenerating neural tissue, will transform themselves into healthy cells of whatever kind is required and thereby replace the degenerated cells.

Rose's presentation of cell development in the foetal brain provides a context that allows us to see that this promise is not entirely fanciful, but he is again cautious in his speculations. Thus, while Rose sees some hope for stem-cell treatments in the case of Parkinson's, where the dysfunction can be localised to the dopamine system, he is less optimistic in cases where neural degeneration is more widespread (as in Alzheimer's).

Throughout, Rose's presentation is scholarly yet readable, and in general he presents a welcome perspective on the brain and cognitive sciences. He is a moderate in a world that has begun to spawn media stars whose stardom is based on dogmatism. He avoids extravagant claims and adopts a cautious style. He eschews dichotomies (such as nature v nurture), arguing that in such cases the truth normally lies somewhere between the extremes, and that the debates spawned by the dichotomies are not helpful for the public understanding of science because they tend to provoke polarised views and support a misperception that science is not objective or progressive.

In fact, a major theme that runs throughout The 21st-Century Brain is the public understanding of science, or more precisely the dangers of the public misunderstanding of science. Rose argues that scientists must not misrepresent the potential of their field, especially in relation to the cognitive and brain sciences, where the apparent miracles promised by technologies such as stem-cell research and the instinctive public distaste of animal research obscure the reality of what progress is likely to bring.

Many people with a scientific background will find The 21st-Century Brain compulsive reading, but odysseys tend to wander - and this book lacks direction. It is not always clear where Rose is going as he leads us on his fascinating journey. This is largely because Rose is not trying to present a specific theory or to make a scientific argument. Rather, his take-home message is to be wary of progress and to consider the ethical issues that science is facing before it is too late. Be comfortable with this, and the journey will be worth it.

Richard Cooper is reader in cognitive science, Birkbeck, University of London.