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Mary L. Phillips Review of The Neuropsychology of Dreams
By Mark Solms

(Brain, 121, 1998)

Mark Solms has endeavored to achieve that which few of us would attempt: an empirical investigation into an as yet ill-defined, if not undefined, area of neuropsychology. As the author states in the introduction when quoting Zeki, 'most would shrink in horror at the thought of investigating what appears to be so impenetrable a problem.'

Yet, with the increasing interest in recent years in the functional anatomy of human higher cognitive functions, including imagery, it is more than appropriate that such a study be performed. Indeed the author emphasizes in the Preface the need for disorders of dreaming to attract more interest, and to be considered as important as disorders of other higher cognitive functions, such as aphasias, apraxias and agnosias.

The book begins with a comprehensive and critical review of the known literature on disorders of dreaming, with especial mention of the Charcot-Wilhrand syndrome, i.e. cessation of visual dreaming or global cessation of dreaming. Even at this stage in the book, the author attempts to unravel some of the confusion surrounding the syndrome, drawing the conclusion that the 'classical' syndrome is in reality a conflation of two separate conditions, and that each may have as its basis a characteristic neurological deficit. The strong relationship between visual dreaming and visual imagery, and the absence or impairment of both in the original description by Charcot, is of particular interest, especially in light of recent studies investigating the neural correlates of visual imagery with functional imaging techniques. There are interesting reviews of the psychosurgical and REM sleep literature, with the author noting and concluding that dreaming and REM appear to be causally independent. Other abnormalities of dreaming are described, including reduced frequency of dreaming, reduced narrative complexity of dreaming, increased frequency of dreaming and recurring nightmares.

On the basis of this extensive review, the author draws several provisional conclusions and hypotheses concerning the clinical and neurological correlates of the various dream disorders, and notes that there is a possibility that a variety of dream disorders may exist, which are as yet unidentified.

The major purposes of the investigation and book are then described: namely. to classify the different disorders of dreaming, to characterize the clinical and anatomical correlates of such disorders and, finally, to formulate a preliminary model of the normal dream process. The study was based on interviews with 361 patients with brain lesions who had been referred to the author for neuropsychological assessment. Such patients were assessed with a structured and comprehensive (dream interview developed by the author in order to obtain a detailed, albeit subjective, account from each individual regarding quantitative and qualitative variables of dreaming, including the extent, quality and sensory modality of the dreams experienced. In addition, a more conventional neuropsychological assessment was performed for each patient in order to establish the relationship between dream disorders and other neurobehavioral symptoms and signs. The neuropsychological findings were then relate(l to structural brain imaging data.

The results of the investigation are (described in terms of the clinical and neurological correlates of four major subclasses of dream disorder, with reference to excellent descriptions of individual cases: non-visual dreaming, global cessation of dreaming, confusion between dreams an(l reality, and recurring nightmares. A criticism is the choice by the author of presenting the neuro-anatomical data only in the form of projections of the original CT and MRI scans on to standard templates. Inclusion of sonic of the original brain images would have been additionally informative. In retrospect, in view of the above-mentioned interest in the functional anatomy of higher cognitive functions, including imagery, it is perhaps a pity that the investigation was not able to employ functional brain imaging techniques to study patients with specific dreaming disorders while they performed, or attempted to perform. visual imagery tasks, or during dreaming sleep. Only in the last chapter is there reference to one study employing PET to study subjects during dreaming and dreamless sleep.

Overall, the author manages to synthesize the large amount of information obtained and to provide a detailed and systematic account of the neurobehavioural arid neuroanatomical correlates of each of the dreaming disorders initially identified. A major point emphasized throughout the book is the distinction between the neuropsychological profile and neural correlates of non-visual dreaming on the one hand and global cessation of dreaming on the other. This distinction is highlighted by the results of the author's own investigation, with the importance noted of bilateral medial occipito-temporal lesions in non-visual dreaming. and of parietal lesions (of either hemisphere) arid deep frontal lesions in global cessation of dreaming.

The final and most difficult aim of the study, a formulation of a model for normal dreaming, is achieved after summary and discussion of the results of the empirical investigation. It is concluded that mediobasal frontal, bilateral parietal and bilateral occipitotemporal structures, together, are of vital importance for this process, although the author stresses the incomplete state of current knowledge of the dreaming process.

Despite the complexity of the subject of investigation, the author presents information systematically and comprehensively. There is an appendix containing an extensive glossary of the nosological terms employed in the book, and good indexing of the cases in the investigation. A minor criticism is that the author appears somewhat over-apologetic at times, for attempting to tackle such a difficult study, when emphasizing the need for further research in this area. The endeavor has, I believe been a success, the book being of interest to all neuroscientists involved in the study of imagery, and of higher cognitive function in general. As an original study, the book provides an excellent starting point for further research in this under-investigated and fascinating area of neuropsychology.

Mary L. Phillips

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