Carl Pfaffmann has been instrumental to the progress in chemosensory research over the past 40 years, both in his personal research efforts and in his training of young investigators who have continued to be productive in the field. Most of the chapters in the present volume were written by scientists who gained experience in Pfaffmann's laboratory, including my graduate school mentor, David Smith. Donald Pfaff has selected 14 topics for the book which review some key current interests of researchers in taste and olfaction. In the first chapter, Carl Pfaffmann presents a brief temporal overview of the study of taste and olfaction, describes some of his most recent work with electric taste, introduces the controversy in taste quality coding between across-neuron patterns and labeled line discriminations, and concludes by proposing that chemical recognition of different tastants may be analagous to antigen-antibody recognition in the immune system.
Chapters 2-4 address several issues regarding taste receptors. Lloyd Beidler and Keichi Tonosaki review electrophysiological evidence from single afferent taste fibers to determine whether all sweet receptor sites are identical or whether multiple types of receptor sites exist. They also discuss the afferent innervation of taste receptor cells and the transduction process. William Jakinovich gives a good review of the electrophysiological and kinetic studies which appear to suggest the existence of an independent sucrose receptor site; then he elaborates on a putative biochemical model for the receptor site. Bruce Oakley details a convincing summary that illustrates the necessity of both chemosensory neurons and gustatory epithelium in the maintenence and formation of mammalian taste buds.
The debate concerning taste quality coding is discussed in chapters 5-7. Marion Frank argues that labeled line discriminations in quality coding are evident because afferent fiber response profiles elicited by taste stimuli correlate with behavioral generalizations (through conditioned taste aversions) in several species. Robert Erickson provides a meaningful review of the definition of taste quality and questions the validity and use of the four basic tastes framework with reference to labeled line and across-neuron pattern views of taste quality coding. David Smith presents a unique compromise to the quality coding controversy by stating that across-neuron patterns are characterized by the responsiveness of particular neuron types, where for each neuron type, similarities among the response patterns exist. In addition, different neuron types are needed to distinguish between response patterns elicited by dissimilar-tasting stimuli.
Chapters 8-10 review taste-related behavior and taste perception. Bruce Halpern discusses the temporal characteristics of taste discriminations in humans and rodents, with discriminations between similar-tasting compounds requiring more sampling time than dissimilar-tasting compounds.