As modern science and medical technology increase the life span of man, the human skeleton is required to function for longer periods of time. Many skeletal problems that besiege the adult stem from abnormalities that exist during infancy and adoles­ cence. These may be congenital problems or acquired problems due either to a child's environment or to some injury sustained during the growth years. Adolescents today are extremely active; many sports and hobbies subject them to an infinite array of traumatizing episodes that may result in injuries and diseases. When I wrote the first edition of The Adolescent Spine in 1976, I felt it pertinent to produce a work which would help medical students and practitioners alike. That edition was extremely successful, not only in this country, but also in many foreign countries. For a medical text, the number of copies purchased was overwhelming­ certifying that the adolescent spine is of serious interest to pediatricians, orthopaedists, physical therapists, physiatrists, medical students, and other allied health practitioners. This new edition has been revised and considerably expanded with this audience in mind. Four chapters have been contributed by authorities with special expertise.

In 1968 we reported that the hippocampus of adrenalectomized rats takes up and retains 3H-corticosterone (McEwen et al. 1968). This and subsequent studies, which were intended to identify and localize sites of adrenal steroid feedback in the central nervous system in terms of putative receptor mechanisms, were stimuli for a variety of investigations into the role of the hippocampus in adrenal steroid feedback on ACTH secretion and on behavior. In this respect, the identification of putative receptor sites was the impetus for the search for the function of glucocorticoids in hippocampus and

The Symposium on the Neural Basis of Behavior, from which this volume was produced, was held at the Alfred I. duPont Institute on June 7 and 8, 1979. It brought outstanding investigators in four fundamental areas of behavioral neurobiology into juxtaposition, there to provide an integrated, multidisciplinary perspective on behaviorally significant brain mechanisms. Particular emphasis was placed on topics of interest to neurobiologists as well as to clinicians in neurological and psychiatric disciplines. The session on central activity states was selected as an appropriate point of departure because the continuum of brain activity states extending from the natural depression of hibernation through the heightened levels of arousal accom­ panying learning is such a clear and basic determinant of behavioral output. The papers on learning and memory outlined diverse approaches to un­ derstanding the basis of these interrelat~d CNS capabilities that constitute the neural basis of behavioral adaptation. Finally, the topics of affective states and mechanisms of pain provided a focus of clinically relevant discus­ sion covering multiple levels of functional and anatomical CNS organiza­ tion.