Hallucinations, a natural phenomenon as old as mankind, have a surprisingly wide range. They appear under the most diversified conditions, in the "normal" psyche as well as in severe chronic mental derangement. As a symptom, hallucinations are a potential part of a variety of pathological conditions in almost all kinds of psychotic behavior. In addition, lately, various psychological and sociological circumstances seem to favor widespread use and abuse of hallucinogens, substances able to produce hallucinations in the normal brain. They not rarely lead to serious psychopatho logy such as toxic, and mobilized or aggravated endogenous psycho ses. While such development adds to our scientific knowledge, it also contributes to our current social troubles. Neurologists and neuro-surgeons, psychiatrists, psychologists and other specialized researchers constantly have been dealing with the phenomenon, its roots and branches, and yet, its primary mechanisms are largely un known. However, investigators of hallucinations now seem to enter common ground on which meaningful discussions and joint approaches become feasible and more promising. We have come a long way from the Latin term "hallucinari", meaning to talk nonsense, to be absent-minded, to the modern con cept of "hallucinations". While the Latin word was descriptive of what may be due to hallucinations, the modern concept defines hal lucinations as subjective experiences that are consequences of men tal processes, sometimes fulfilling a purpose in the individual's mental life.

First published in 1991. The purpose of this book is to be used as a clinical guide to assist the clinician in making a comprehensive clinical evaluation of hallucinatory symptoms as they present in various conditions, psychiatric and otherwise. Except for a few chapters that deal with theoretical background on the subject, the focus of most of this book is on clinical manifestations, diagnostic issues, and treatment ap proaches with regard to hallucinatory symptoms.

The work aims to provide an overview of the field of contemporary hallucinations research. It will consist of 28 chapters, the writing of which will be put out to international experts specialized in the specific fields at hand. The work aims to be unique, in that it intends to cover many different types of hallucination, and to approach the subject matter from four different perspectives, i.e., conceptual, phenomenological, neuroscientific, and therapeutic.

The Dictionary of Hallucinations, second edition, is an alphabetical listing of issues pertaining to hallucinations and other misperceptions. They can be roughly divided into four categories: 1. Definitions of individual hallucinatory symptoms 2. Medical conditions and substances associated with the mediation of hallucinations 3. Historical figures who are known to have experienced hallucinations 4. Miscellaneous issues Each of the definitions of individual hallucinatory symptoms includes: a definition of the term its etymological origin the year of introduction (if known) a reference to the author or authors who introduced the term (if known) a description of the current use a brief explanation of the etiology and pathophysiology of the symptom at hand (if known) references to related terms references to the literature The second edition of A Dictionary of Hallucinations serves as a reference manual for neuroscientists, psychiatrists, psychiatric residents, psychologists, neurologists, historians of psychiatry, general practitioners, and academics dealing professionally with concepts of hallucinations and other sensory deceptions. This new edition provides updated information and references, and includes newly discovered hallucinations, bringing together contributions by other authorities within the field, with all the entries edited by Prof. Blom.

There has been a recent surge of interest in auditory hallucinations (AH) in schizophrenia compared to those experienced by non-clinical (i.e. healthy) individuals. This interest stems in no small part from a keen awareness of the fact that progress in developing more effective treatments for AH in psychosis has been seriously hampered by our limited understanding of the cognitive and biological mechanisms involved. The prevailing notion that AH in clinical and non-clinical populations share the same features and underlying mechanisms - the continuum hypothesis - has been seriously challenged by a growing list of differences, as well as similarities, between these groups. At the phenomenological level this is exemplified in the highly negative content of AH in patients and the markedly earlier age of onset of AH in non-patients. Similarly, several recent studies point to significant differences in cognition, language lateralization and, possibly, dopamine function between these groups. These findings have important implications for the design of future studies, and raise considerable doubt about the adequacy of modelling the functional mechanisms of clinical AH on the basis of non-clinical populations. In short, the time seems ripe to re-evaluate the continuum hypothesis and provide a forum to present alternative perspectives on the functional pathways leading to AH in clinical and non-clinical groups. Such a forum is also timely in view of the renewed interest in AH in other (non-schizophrenic) clinical groups, again examining similarities and differences between such groups. Preliminary studies, for instance, have shown that AH in certain clinical populations (e.g. bipolar disorder, borderline personality disorder, dissociative disorder) share similar phenomenological features with AH in schizophrenia. However, the implications of such findings are not fully understood, and studies have not adequately examined potential differences between AH in these groups. The goal of this Frontiers Research Topic, therefore, is take the opportunity to bring together research exploring differences and similarities in mechanisms of AH in clinical and non-clinical groups and to stimulate the development of new explanatory models which explicitly link the phenomenological characteristics of AH with underlying mechanisms.

With the wit and compassion of Oliver Sacks and with psychological detective work worthy of Sherlock Holmes, Siegel reveals the cartography of the hallucinatory world through 17 riveting cases.