%europmcholocgia, Vol. 28, No. 7, pp. 755 757, 1990. Pergamon Press plc. Printed in Great Britain.

BOOK REVIEWS

Perspective in Memory Research. Edited by M. S. GAZZANIGA, MIT Press, 1988.

Enriched and Impoverished Environments: Effects on Brain and Behavior. By M. J. RENNER and M. R. ROSENZWEIG, Springer-Verlag, 1988.

As THE 1980s drew to a close, research on memory and learning became the focal point of neurobiological interest. Earlier seen as approachable only by psychologists, or perhaps psychopharmacologists, and a brave but hazardous theme for neurochemists or physiologists, the molecular and cellular mechanisms of memory consolidation have suddenly become accessible and popular topics, both for major grant-givers (vide the Japanese Human Frontier Science Programme) and aspirant graduate students. It took Gazzaniga's edited collection, however, to reveal to me that this interest extended as far as the Xerox Corporation and the U.S. Army, which sponsored Perspectives in Memory Research. Gazzaniga's explanation of this interest is simple; a volunteer army, he argues, is of lower educational standard than a conscript one whilst at the same time military equipment is getting more and more sophisticated. Can neurobiological research enhance memory skills and hence improve training? Without wishing to comment on the relative educational attainments of U.S. draftees and volunteers, I find this rationale not wholly convincing; I suspect that the simple answer to such a question would be no. Whilst researchers are never keen to look gift horses in the mouth, I must declare my own interest as one who has always worried that the military horse may turn out to be Trojan and should be kept a good hooves length away from my laboratory.

Nonetheless, Gazzaniga has done his sponsors proud in assembling a group of authors to review current U.S. research thinking on memory with perspectives ranging from the molecular to the psychological. However, the lack of integration between these levels is tacitly admitted by the division of the book into two sections, respectively on neurobiological and on psychological aspects of the field. The four chapters of the first half are dominated by two substantive reviews. The first is by Lynch and Baudry on structure function relations in the organization of memory, focusing on the topography and wiring of the olfactory cortex and hippocampus as memory systems, and very much reflecting Lynch's newer concerns with modelling approaches rather than the biochemical hypotheses which this pair of reviewers made very much their own earlier in the decade. The second major review, by Sej nowski and Rosenberg, continues in similar vein by summarizing the state-of-the-art view of connectionist models of learning and representation. It must be for the working neurobiologist to decide how far such theory-driven modelling is helpful in interpreting observational data derived from the study of real learning and memorizing brains.

If the U.S. army's concern with the neurobiology of learning is directed at improving training of recruits, such modelling seems remote from its immediate concerns, though of more relevance to the burgeoning field of neural computing which has become one of the most significant potential technological outputs to learning and memory research in recent years for both industrial and military sponsors. Trainers are more likely to find the practical orientation of some of the chapters of the second half, such as Hirst's simply-entitled "'Improving memory", which begins from a consideration of the layout of instrument panels and how actors learn scripts, and Kosslyn's emphasis on the use of imagery, of more immediate relevance, though it is not clear to me that there has been much advance in Lhis field since Cicero's simple advice on remembering oratory two millenia back. In conclusion, Hirst and Gazzaniga summarize the take-home lessons of the review chapters and end with a traditional call for more research. His sponsors should be pleased; whether graduate students will take to the book as an alternative to the new textbook by Dudai on the neurobiology of memory (Oxford University Press, 1989) which is otherwise set to become the standard in the field, remains to be seen.

The pioneering work of the Berkeley group on the neural consequences of rearing rats in highly restricted ("impoverished") versus somewhat less isolated and unnatural ("enriched") conditions, led since the early 1960s by Mark Rosenzweig, is a standard feature of any neuroscience textbook. The demonstration that the conditions under which animals were reared could affect such parameters as cortical thickness, neuronal and neuropil density, as well as biochemical measures such as activity of a number of transmitter-related enzymes, was important when first made in helping loosen up earlier conventional wisdom about the lack of postnatal plasticity of the brain, and it is a measure of how far we have come in no small measure as a result of the Berkeley group's work that today it is very much taken for granted. In their short text Renner and Rosenzweig summarize and review a quarter-century of neurobiological data gathered using the enriched/impoverished environment model, and, perhaps more important, provide a penultimate chapter (the final chapter discusses possible medical and agricultural applications of the llndings) which attempt to set work which has sometimes seemed to be very empirically-based into a more structured theoretical framework Just what is it about the differing environments which generates the neural

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756 BOOK REVIEWS

changes? Can a common psychological, and/or hormonal mechanism or pathway be involved. What relevance do the Berkeley studies, now also extensively developed by Greenough and his colleagues at Urbana, have to the neural plasticity associated with more specific paradigms of learning and memory formation? How far can the effects he mimicked or modified by combination with transmitter-related drugs'? This short book is to my mind the best available summary of evidence derived from the Berkeley environmental paradigm, and its format is likely to ensure it wide utility.

STEVEN P. R. Rost~

Memory and Central Nervous Organization. By CHARLES M. FAIR, Paragon House, pp. 203.

MEMORY is one of the most intriguing dilemma of our mind and the most studied higher brain function. The literature on this topic is very difficult to approach because, compared to other cognitive functions, memory has been widely investigated from the most different points of view. A number of studies coming from psychology, neuropsychology, neurophysiology and biochemistry are available. All of them are, sometimes constrained by the theoretical framework of their own field and by the different technical approaches; nevertheless there are some interesting attempts to link the gap between the various levels at which memory is analysed. Even if some conclusions are biased, a more general view on the argument could both stimulate new ideas and offer precious analogies amongst different kinds of observations. This approach is adopted in the book Memory and Central Nervous Organization written by C. M. Fair.

The author announces in the preface that the book relates to some questions raised at the Henry Ford Hospital Symposium on the Reticular Formation of the Brain (Detroit, March 1957). The topics presented in the book relate to memory in that they concern the "vertical organization of the central nervous system, and the way in which the reticular, limbic, and mesolimbic systems may action jointly to steer attentional processes or to regulate the conditions making for memory formation in the neocortex". The first question introduced by Fair is whether or not the neurophysiological behaviour of CNS neurons is in keeping with a function of storing information. The assumption is that a memory forming system should not be set early in life. He quotes Blackmore: "Perhaps it is mere probability of experience that determines the final preference of a cell. Perhaps each neuron selects, as its preferred stimulus, the feature that it has seen most often". Then the ratio between "committed" and "'uncommitted" neurons is not hard-wired and the neurons working on what Fair calls Blackmore's principle are by definition "memory forming" (Chap. 1). He points out that, al though it seems from the early work of Hubel and Wiesel that some structures in thalamus and neocortex set up by structured input from the periphery become fixed at maturity, there are some data in adult cats showing an increase of "uncommitted" cells in primary visual cortex under particular experimental conditions. These and other results, related to the observations in human sensory deprivation, are discussed in Chaps 4 and 5. The author also suggests that neurons not subjected to special fixing mechanisms arc good candidates for subserving short-memory functions, The difference between these neurons and those of temporal association cortex having the mechanisms of Long Term Potentiation (LTP), are discussed in Chaps 6 and 13. The pre-synaptic model of learning, proposed by Kandel and Schwartz, is considered by Fair "paradigmatic for the acquisition of motor skills". In contrast the post-synaptic model of learning, studied by Linch and Baudry, is viewed as the way in which cognitive skills are acquired. Fair goes further, relating these two mechanisms to the distinction made by some authors between "procedural" and "'declarative" knowledge.

Chapters 2 4 deal with many aspects of cortical structure, while Chaps 8 13 have to do with caudo-rostral organization of the nervous system, beginning at the level of n. ,qiqantocellularis. The findings discussed in these chapters lead the author to the conclusions outlined in Chap. 7. Here a model of cortical organization is proposed in which an horizontal aspect (interareal) and a vertical component (intracolumnar) provide the basic circuits for memory functions.

Once a neuroanatomical model subserving different types of memory is provided one can ask what is thc physiological mechanisms responsible for the stabilization of memory trace. Fair claims that such a mechanism is active during sleep. He tries to show, in Chap. 5, that two phenomena are strongly related and, in some way, functionally complementary: Slow Wave Sleep (SWS) and REM sleep (REM-S). He thinks that both phenomena act "'to reduce central nervous entropy", one being the expression of an intracellular mechanism of metabolic recovery of neurons and glia (SWS), the other (REM-S) acting at intercellular level "'by intervals of activation whose effect is to conserve acquired structure in the network". He also comments that this proposal is in keeping with the fact that the REM-S has appeared late in evolution when some "open" cortical areas (not-preprogrammed, "uncommitted") have started to be included in the brain.

Those outlined above are some of the most compelling questions faced by the author in this book. It can be considered an important attempt to coherently organize an enormous amount of data coming from different fields of research and is a useful reference for people who, studying memory from a very specific point of view, want to deepen their knowledge of the field. For these reasons I should highy recommend it.

ANNA BERTI