The recent emergence of the field of social cognitive neuroscience has been accompanied by an increasing number of studies aimed at uncovering the neurobiological basis of the self. For instance, several studies have now been published using functional neuroimaging to uncover neural responses to self-related processing in healthy subjects. Complementing this approach, important insights regarding the brain and the self can be obtained from studying neurological and psychiatric conditions that affect the self. Examples of such conditions are frontal lobe impairment, autobiographical disorders, dissociative disorders, schizophrenia, and autism. The Lost Self, edited by Todd E. Feinberg and Julian Paul Keenan, addresses both types of research endeavors. The reader gets even more: a perspective from philosophy and a first-person account.

After a short introduction (Chapter 1), philosopher John R. Searle discusses the self as a problem in philosophy and neurobiology (Chapter 2). He briefly alludes to different ideas about the self—which in philosophy traditionally regards the problem of personal identity—that have been put forward by Descartes, Hume, Locke, and Kant. Searle persuasively argues that the first-person perspective of “unity of our conscious field” is central to understanding the self. The subjective contents of consciousness require a principle of unity, but the principle is not a separate entity. According to Searle, the “irreducibly mental unified conscious field is a biological and, therefore, ‘physical’ or ‘natural’ feature of the brain.” Chapter 3, by Gillihan and Farah, addresses the question about whether one can map this biological feature of the brain using functional neuroimaging. More specifically, the chapter provides a thought-provoking, critical methodological overview of functional imaging studies of self-processing. The authors show that the studies that have been reported are hampered by significant conceptual and empirical problems. First, definitions of self are heterogeneous and often vague or circular. Second, a number of studies compare a self-processing condition to a non-self-processing condition, but fail to adequately control for dissimilarities between both conditions, such as differences in cognitive load or affective content. These are potentially confounding factors that may explain the differences in activation between self and non-self conditions. In several studies subjects are imaged while making judgments about trait adjectives. They are asked to indicate whether these are self-descriptive or not. Contrasting brain activation during the former and latter conditions would reflect self-processing. However, as Gillihan and Farah point out, it could be argued that both conditions must engage the self-concept in order to decide whether an adjective is self-descriptive or not. Gillihan and Farah doubt whether the self can be localized in a specific brain region or network, and even go on to suggest that “our vivid awareness of a self, like awareness more generally, may not be explicable in terms of the mechanistic workings of the brain” (p. 30).

In following chapters, Feinberg describes a theory of neural hierarchies of the self (Chapter 4) and Stuss et al. discuss the role of the frontal lobes in self-awareness (Chapter 5). In Chapter 6, Fujiwara and Markowitsch review the neural basis of autobiographical disorders, in which retrieval of personal past experiences is seriously impaired. Psychogenic amnesia is an example of a dramatic case of autobiographical memory loss, in which severe emotional stress or self-related problems can correspond to a total block of memory contents. Autobiographical disorders in neurology and psychiatry rarely correspond to circumscribed regions in the brain but may instead arise from lesions or functional disturbances in the distributed network underlying autobiographical memory: hippocampal formation, medial prefrontal cortex, ventral frontal cortex, and posterior association cortex. Chapter 7 (by Goldenberg) concerns body image and the self and makes a strong case for the conclusion that body image is a fragile result of fleeting integration of current perceptual inputs, prior experience, and culturally acquired knowledge. For example, the “rubber hand illusion” shows that a rubber hand can easily be integrated into the image of one's own body, thereby dissolving the border between one's body and external objects. Furthermore, Goldenberg discusses evidence that image of the unity of the body may be distorted, as when patients with hemineglect neglect one half of their body. In his discussion of phantom limbs he points to intriguing evidence regarding the occurrence of phantoms in children with congenital absence of limbs. Because these children have never experienced an intact body, their phantoms might be interpreted as manifestations of an innately predetermined body image that unfolds even without any support from experience. This is not necessarily so, however, because it could be argued that the brain has enough plasticity to transform knowledge about the universal structure of bodies into a convincing proprioceptive sensation of having a complete body conforming to this universal structure. A limitation of this chapter is that it does not discuss body dysmorphic disorder.

The next two chapters both focus on a group of neurological disorders of the self: delusional misidentification and delusional reduplication syndromes. An example is Capgras syndrome, which refers to the belief that a person or persons have been replaced by “doubles” or imposters. Feinberg et al. (Chapter 8) discuss this and other related syndromes and argue for a specific role of right frontal pathology. Spangenberg (Chapter 9) discusses cases of delusional misidentification of the self in a mirror (e.g., an older woman who saw the image of herself as a little girl when she looked in the mirror). Spangenberg advances an explanation in terms of a mismatch between top-down processing (generating a hypothesis about what one is perceiving) and bottom-up processing (incoming information from the senses) triggered by a new onset deficit interfering with visuoperception. This results in the hypothesis of a stranger in the mirror the next time the person looks into a mirror. She further suggests that a person who feels disconnected or alienated in some way (e.g., due to the ego dystonic nature of new onset faulty perception after some form of brain damage) may be biased to evaluate the faulty hypothesis as reasonable. This account acknowledges the complex interplay of neurocognitive and emotional factors in delusional misidentification.

Other chapters in this fascinating volume deal with disorders of the self in dementia (Seeley and Miller, Chapter 10), the self and lack of empathy in autism (Baron-Cohen, Chapter 11), misattribution of agency in schizophrenia (Blakemore, Chapter 12), and the neural correlates of depersonalization (Kober et al., Chapter 13). The book concludes with chapters on the self in dreams (Revonsuo, Chapter 14), psychoactive agents and the self (Mathew, Chapter 15), and meditation and the self (Lou and Kjaer, Chapter 16). Although the chapters are generally well written, in some places concepts remain undefined (e.g., the “mental self”, Chapter 16) and Chapter 15 makes continuous reference to ancient philosophical thought from India, which might be less appropriate for a chapter on psychopharmacology. The final chapter provides a moving first-person account of brain stem stroke survival by the distinguished sleep researcher J. Allan Hobson (Chapter 17). In spite of life-threatening insults to his brain stem, lungs and heart, the essence of his self as an observing, reasoning scientist remained intact. Hobson therefore emphasizes the resilience and durability of the self in the face of major insults.

In summary, The Lost Self brings together contributions from renowned researchers from neurology, psychology, and philosophy to explore the neurobiology of the self. It nicely complements the first book on this subject, published a couple of years ago (Kircher & David, 2003). Both books are a must-read for any student of the neural underpinnings of the self and self-related disorders. For the time being, however, the reader will encounter more questions than answers.