Toppling creation's crown

Despite its seemingly nit-picking title, Richard Cytowic's book should be a rich source of information and inspiration for anyone working on, or thinking about, the brain. The remit of the neuropsychologist is stated at the outset as explaining human behaviour in terms of brain function. We learn that there are even two different sorts of neuropsychologist: one trying to "rule in brain damage" and the other trying to "rule it out".

Cytowic clearly belongs in the first camp. However, he is no neurotechnocrat kowtowing before the objective and immediate diagnostic revelations provided by the burgeoning welter of information from brain imaging. Rather, we see that the value of such a neuropsychologist who tries to "rule in" brain damage, is to provide insights into the significance of certain types of lesion, both in terms of prognosis for an individual patient, as well as for furnishing more general information about how the brain works.

The Neurological Side of Neuropsychology is unashamedly a textbook, even at the most cursory glance: there are two chapters on how to examine a patient and how to perform a formal neuropsychological assessment. Within the first few pages the reader is encouraged to perform as many brain dissections as possible, always to seize the opportunity of examining a patient, and to take no one's word over first-hand observations. On the other hand, the first quarter of the book is mainly given up to "conceptualisations" that would be of interest to a far wider audience.

Cytowic offers an authoritative yet concise survey of the history of brain research, with a critical emphasis on how ideas were supplanted or corroborated by those of succeeding generations. It would be edifying even for the more seasoned neuroscientist, used to working "bottom up" with individual neurons and specific neuronal circuitry, to read how a detailed knowledge of cell morphology and neuroanatomy did not prevent those such as Paul Yakovlev or Paul MacLean from having holistic visions of how the brain might be put together.

It is when we arrive in the present era of brain research, however, that Cytowic's opening chapters have particular value. Even today the approach and assumptions adopted by many, if not the majority, of the neurocommunity may not, after all, be the way to go. The narrative is suffused with cogent arguments against the currently fashionable neuro-holy cow: computation. One thrust of the argument is that the brain functions not, as was once thought, hierarchically, but, as is now widely accepted, in parallel: hence when it comes to the outer layer of the brain, the cortex, its functional importance as the neurological crown of creation, has been overestimated. Nonetheless, this persistent but now outdated enthusiasm for the cortex has led the majority of brain researchers into placing too great an emphasis on the purported feature of the cortex, "reason and logic". In turn, we see how our admittedly awesome human abilities for these "higher" functions, has inspired artificial models of the brain based mainly on the cortex and a computational manner of brain functioning. Cytowic redresses the balance in showing how emotions are an important and integral component of our mentation repertoire, how diffuse chemical systems link brain regions, and how the limbic system and other subcortical structures are orchestrated along with the cortex to give rise to the net product, one's state of mind.

Such arguments are timely for anyone, not just the neurocommunity, interested in consciousness: they emphasise the emotional tone that underpins all our subjective experience and thus reveal the inadequacies to date of AI strategems. As is the way of textbooks, however, there is no personal credo built up through successive chapters, no grand conclusions, nor any personal theories. Cytowic devotes most of the remainder of his book to conveying information. In one chapter he starts with specific regions of damage and catalogues the behavioural consequences. But for most of the book, he tends to travel in the opposite direction: he begins with certain phenomenological impairments, and then tries to trace them back to their brain origins.

This is a sophisticated book that requires an already informed reader to use established knowledge to challenge accepted concepts and think about new ones. It is eloquently written, although not lavishly nor pedagogically illustrated. It is an unconventional textbook requiring an unusual amount of reflection: as such it will not succeed as a start-from-scratch introduction for either aspiring neuropsychological students, nor for the non-neuro consciousness aficionado seeking an introduction to the brain. On the other hand, once the more conventional primers had been respectively assimilated, Cytowic's contribution would be of enormous value to both neuro-professional and general readerships.

Susan Greenfield is a lecturer in pharmacology, University of Oxford.