This volume provides a unique, comprehensive, multifaceted perspective on hallucinations. The editors have brought together an international cast of authors to provide 27 chapters, organized into 5 parts. Part I covers the “basics,” including details of history, epidemiological data including base rates of hallucinatory experiences in the healthy population, and assessment methods. Part II deals with “cognitive models” of hallucinations, with emphases on “top-down” versus “bottom-up” models, the roles of speech, language, memory, and monitoring processes. Part III examines neurobiological and computational models, with an emphasis on developmental and genetic mechanisms, along with animal models linked to hallucinogenic drugs. Part IV explores the emerging literature that is interrogating the mechanisms of hallucinations using neuroimaging, and includes studies of EEG, MEG, structural and functional MRI, and connectivity studies. Part V looks at therapeutic strategies, spanning psychotherapy, psychopharmacology, and neuromodulatory methods including transcranial magnetic stimulation.
This abbreviated summary makes clear that few stones have been unturned in an effort to provide not only breadth but also depth of coverage, and scholars will find here ample representation of the majority of theoretical views on this intriguing topic. An advantage over the few monographs that address hallucinatory behavior is that this edited volume surfaces multiple contrasting and occasionally competing views, thus enriching the coverage of the topic and helping readers see more clearly where the experts lack concordance of opinion.
Among many interesting theoretical topics raised is the centrality (or lack thereof) that auditory verbal hallucinations (AVHs) enjoy with respect to the diagnosis of schizophrenia. Multiple chapters cover the widespread occurrence of AVH in healthy people (“voice hearers”) and other neurological and neuropsychiatric syndromes, highlighting the dimensional rather than categorical nature of hallucinatory experience. A related intriguing bit of evidence is provided by David and Rapoport (Chapter 12), who, in describing their childhood onset schizophrenia (COS) studies, highlight results showing how IQ is related to the breadth of hallucinatory experiences. Specifically, highest IQ was found in COS patients who had only visual hallucinations, lower IQ was found in those who also had either somatic or olfactory hallucinations, and lowest IQ was found in those who had hallucinations spanning all three modalities. Other contributions further highlight the importance of viewing hallucinatory experiences as phenomena that span many syndromes, and that may parallel generalized brain dysfunction, rather than being a characteristic of any particular diagnostic group.
Clinicians may particularly enjoy learning more about the assessment of hallucinations. Widespread clinical practice often reduces assessment of hallucinatory experiences to a few broad categorical judgments. Stephane (Chapter 5) details more than 30 qualities, and summarizes findings suggesting that three dimensions may characterize hallucinations: inner–outer spatial location; self-other attribution; and linguistic complexity. Instrumentation reviews offer a cogent perspective and should enable the neuropsychologist to determine what tools may be most useful for either clinical or selected research applications.
The cognitive models all tend to emphasize a role for speech and language mechanisms as these intersect with other central or higher order monitoring systems that lead to misattribution of source. Several models emphasize further the critical roles played by exogenous and endogenous emotional stressors, helping to explain the unusual and unique content of hallucinatory experiences. Most familiar to neuropsychologist readers are likely to be the functional anatomic, genetic, and neurochemical models, and particularly those which emphasize monitoring failures and the speech-language systems. These reviews may be particularly valuable in highlighting for neuropsychologists the mechanisms that must be operating when they do observe hallucinatory phenomena in their patients. There is sometimes still a tendency in clinical neuropsychology to view hallucinations as attributable to a psychiatric syndrome, rather than to specific patterns of brain dysfunction. The models illustrated in this book help to put hallucinations and their likely causes in a clearer perspective.
The second half of the book (Parts III–V) provide solid coverage of modern neural network models that have led to some strong hypotheses about the plausible mechanisms underlying hallucinations in the brain. These models are juxtaposed with evidence from a broad range of experimental approaches spanning electrophysiological recordings and structural and functional brain imaging methods. These models are helping tie together diverse theoretical elements advanced in the cognitive models, and increasingly generating a more unified view of hallucinatory experiences spanning molecular, cellular, systems, and cognitive levels of explanation.
Overall, The Neuroscience of Hallucinations provides a welcome and valuable collection of works on hallucinatory experience that is unprecedented in its scope. It must be acknowledged that the works come from a renowned international group of scientists and the English is occasionally uneven; it is a credit to the authors and editors that all contributions are sufficiently lucid for those of us who speak only English. The substantive contents of the book are of high value to neuropsychologists, however, by providing a deeper insight into the relatively common but poorly understood phenomena of hallucinations. By placing these hallucinatory experiences more firmly in the framework of brain-behavior theory, further progress in both the science and practice of neuropsychology is likely.