BioI@xaf Psy&&gy 31 (1995) 193-199 North-Holland

193

BOOK REVIEWS

The discovery of the endogenous opioid neuropeptides and the different types of opiate receptor in the 1970s provided new challenges for the behav- ioural neuroscientist committed to the study of the neurochemical control of behaviour. This edited, multi-authored volume shows how this challenge has been met by considering the roles of opioid neuropeptides in drug dependence, reinforcement, tolerance and drug discrimination, analgesia, food and water intake, social, sexual and exploratory behaviour, learning and memory, “neu- robehavioural development” and clinical applications_

How well the enterprise has fared so far in the eyes of the various authors is perhaps to be gauged by the generally more optimistic tone of the neurobio- logical overview by Akil, Bronstein and Mansour. In what is the most stimulating of all of the contributions, these authors emphasize the obvious links with the genetic control of neuropeptide synthesis and expression and also discuss the functional implications of mapping the opiate receptor sub- types in the brain. In an incisive passage, they outline the conceptual problems inherent in studying opioid functions, pointing out, for example, the Iimita- tions of approaches based on analyses of the effects of the opiate antagonists such as naloxone, “which fails to discriminate between opioid systems, recep- tor types and anatomical locations”. This advice turns out to have come too late for the most part? as the evidence reviewed by many of the chapters depends heavily on interpreting the effects of low (and sometimes high) doses of naloxone. This is, of course, a necessary preliminary step, but it rapidly becomes apparent that many of the psychopharmacological analyses have not gone very far past these preliminaries, Although Nyberg and Terenius indicate in their chapter the possible applications of more specific techniques to psychiatry, it is clear for the most part that the behavioural analysis of opioid functions has been hampered by the lack of selective pha~acolo~cal tools and by the reluctance, either of behavioural scientists to apply themselves to more sophisticated neurobiological techniques, or of neurobiologists to col- laborate with psychologists. Although the likely utility of selective lesioning of

194

the central endorphin pathways is recognized by the author of one of the chapters, the claim that this is possible by using monosodium glutamate is sadly unwarranted. It was, however, amusing to see how, in their chapter, Colpaert and Shearman used a “top-down” analytical approach from studies of drug discrimination learning to turn the tables on the molecular biologists and make inferences about the conformational nature of opiate receptors.

The phrase “ behavioural processes” figures strongly in the title of the book, but it might easily have been “behavioural responses”, because there is little attempt to dig deeper than the surface structure of the observed behaviour. It would have been interesting for someone to have grappled with the sheer diversity of opioid systems in the peripheral, as well as the central nervous system, to consider the question of whether a unitary or co-ordinated func- tional action for these substances is at all plausible, as both Margutes and Panksepp have bravely speculated in the past. One form of psychological theory that has drawn heavily on the behavioural effects of opiate drugs is the opponent motivational theory of Solomon and others ~ but I could find no mention of this in the index. An “involvement” of opiates in reward of reinforcement processes is, of course, predicated from the phenomenon of

narcotic drug abuse. Bozarth provides a competent resume of his excellent experimental work with Wise on the neural basis of opiate addiction, in which the logical device of dissociation of function is used to infer that withdrawal is not a necessary condition for opiate abuse.

For many of the chapters, it would also have been wise to point out that it is one thing to demonstrate a pharmacological effect on various appetitive or

consummatory forms of behaviour, but quite another to explain why such effects occur or whether they have any significance for understanding normal or abnormal brain function. Thus, the inhibition of copulatory behaviour in male rats by low doses of intraventricular /Lendorphin, reviewed by Serra et al., is put down to a role for this substance in the “regulation” of sexual behaviour. But it is not clear what this means. Is sexual motivation reduced? (Studies of instrumental rather than simply consummatory responding would suggest not.) And extrapolations of the facilitatory effects on mounting in rats of antagonists such as naloxone may be unduly enthusiastic; it is not men- tioned that the stimulator effect of naioxone in the rat is not found in

experimental primates. The chapter on endorphins, exploration and activity (by R.J. Katz) pas-

tulates a role for opioid in exploration, largely on the basis of a somewhat confusing set of pharmacological effects of drugs on various component of activity. Processes of selective attention are also invoked, but not in an operationally cogent manner. The overall conclusions are not very promising: for example, “Morphine clearly altered exploration, but in a behaviourally complex manner”, and “While opioids may be implicated in many aspects of exploratory behaviour, little agreement exists beyond this point”.

195

Overall, there is an implicit faith in a book with this type of organization of some form of ‘chemical coding’ of behaviour. This may, however, be a misleading perspective because there is little reason to suppose that behaviou- ral processes or responses will necessarily fractionate so easily along these lines. It is salutary to consider that the role of opioid neuropeptides in behaviour (as well as that of other neurotransmitter and modulators) may be more analogous to that of specialized components which enable the operation of wholly independent electronic circuits, dependent on the sequentiai oper- ation of anato~cally defined projections using different neurotrans~tters at each step. In that case we may be best advised to study how that specialized component works, rather than pay too much attention to the multifarious behavioural responses in which it inevitably participates.

Endorphins, Opiates and Behavioural Processes does summarize many of the intriguing effects of opioid compounds on behaviour, including potentially important actions on learning and memory and analgesia in natural settings, as well as those mentioned earlier in the review. As a beginner in the field, I found the book very useful for rapidly bringing me to the forefront of knowledge. The book is attractively produced, although the editors have been overly kind to their contributors in allowing certain idiosyncrasies of style. It would have been greatly enhanced by a more uniform theoretical, as well as stylistic, approach.

Trevor Robbins Department of Experimental Psychology,

University of Cambridge

M.D. STORFER, Intefiigence and Giftedness: The Contributions of Heredity and Early Environment (Jossey-Bass, Oxford, 1990) pp. xxii + 636, $35.00

This book is probably one of the most exhaustive compilations to date of research on environmental factors affecting IQ. In its review of some 900 research studies, it covers such diverse topics as prenatal environment and birth-weight, birth order, mother-infant interaction and child-rearing prac- tices, effects of adoption, effects of improved healthcare practices, and special cultures such as the Israeli kibbutzim. As a source-book for investigators it will have considerable value. It also has some unexpected practical implications. For instance, it suggests that the tradition of swaddling infants actually enhances the quiet alertness associated with perceptual learning in early childhood.

There is, however, a rather different aspect of the book, which is the presentation of a neo-Lamar&an account of the evolution of IQ. The author claims that the general increases in measured IQ observed in the twentieth century are too great to be accounted for by environmental factors alone. He