The Human Illnesses: Neuropsychiatric Disorders and the Nature of the Human Brain

A vigorous yet unstable orphan, neuropsychiatry was conceived from the antipodal chromosomes of the Enlightenment's scientific revolution and of the Romantic Era's insurrection against such. As its very name implies, neuropsychiatry is both bridging and divisive. Objectivity, observation, description, empiricism, and rationality are pitched in a relentless, yet productive, struggle with the subjective, spiritual, irrational, intuitive, inventive, and imaginative. It is no wonder that the parent specialties of neurology and psychiatry both embrace and disown our subspecialty.

Historically, “lesion” became, and in many ways remains, the lens of classical neurology. A severed anterior interosseous nerve (a motor branch of median nerve) leads to weakness of the flexor pollicis longus (the flexor muscle of the thumb) and of the flexor digitorum profundus (the flexor muscle of the distal phalanges of the thumb and index finger). Oh how intellectually satisfying, unless it afflicts you—the reader of this book review—and you wish to turn the page of this Journal with the affected hand. As applied to our understanding of the brain functions and dysfunctions conventionally subserved by neuropsychiatry and psychiatry—such as mood regulation, motivation, social behavior, reality testing, abstract thinking, judgment, and intelligence—lesion-based insights are both elusive and enlightening. Today, the lenses for lesion discovery in psychiatry and neuropsychiatry comprise functional brain imaging, cellular and molecular biology, basic neuroscience, and genetics. For example, components of complex brain-based disorders like depression have been illuminated by lesions such as a polymorphism within the promoter of a serotonin transporter gene that has been linked to psychosocial vulnerability to stressful experiences (1, 2). Nonetheless, neuropsychiatry must express and exert caution when advocating that this approach be applied to far more expansive terrains.

In the preface to their book, Peter C. Williamson and John M. Allman articulate their ambitious intent: “Our thesis is that the neuronal pathways that underlie neuropsychiatric conditions mirror unique human capabilities. Determining how these capabilities are represented in the human brain not only tells us about what makes the human brain human but also provides a framework for understanding neuropsychiatric disorders in a new way, much the same as the circulatory system provided a framework for understanding heart failure at the beginning of medicine 400 years ago” (pp. vii–viii). Let us term this method “neuroanalysis.” The distinguished authors draw upon and blend their extensive experience and remarkable scholarship in neuropsychiatry (Dr. Williamson) and in evolutionary biology (Dr. Allman) to accomplish this goal. If only, however, the computer were a pump.

In the initial pursuit of their grand goal, the authors provide a cogent overview of basic neurodevelopment, regional structural and functional neuroanatomy, neurotransmitters, and neuronal circuits. Interspersed in this exploration are engaging facts and insights gleaned from evolutionary biology. For example, in depicting “unique aspects of the human brain,” the authors reveal that Von Economo neurons, a vital class of neurons located in layer 5 of the anterior cingulate—in both cognitive and affective processing regions—and in the fronto-insular cortex can be found only in humans, great apes, elephants, and whales. The authors hypothesize that these neurons may be involved with the capacity for self-control through the recognition of having committed an error. They suggest that the anterior cingulate and fronto-insular cortex connect with areas of the brain storing information related to past experience and seemingly mediate social behaviors based on this experience.

In chapters 4–7 of their text, the authors seine prominent and prototypical neuropsychiatric conditions through fine nettings of epidemiology, genetics, brain imaging, neuropsychology, neurobiology, and neuropathology in order to capture aspects of the CNS that might be uniquely human. The disorders considered are schizophrenia, bipolar disorder, autism, attention deficit hyperactivity disorder (ADHD), anorexia nervosa, and frontotemporal dementia. Often reconceptualizing the essences of the respective illnesses through recent evolutionary and neurobiologial advances, these explorations are exhilarating. For example, they convincingly posit that ADHD is a primary deficit in motivation rather than a deficit in attention. In making their case, the authors deftly review the recent research revelations about the neurocircuitry, neurogenetics, neurobiology, and neuropathology of the brain's primary reward system—the dopamine system—as it would relate to the symptoms and treatment of patients with ADHD.

In chapters 8–12, Professors Williamson and Allman highlight and explicate what could be considered “hot topics” in the social, cognitive, and behavioral neurosciences from neuropsychiatric and evolutionary biological perspectives. Such intriguing concepts as “the social brain,” “stimulus independent thought,” and “default networks” are explored, and vexing questions such as “Do animals have a theory of mind?” are raised and answers tendered. Insights about the human brain are sought through the neuroanalysis of humor, empathy, disgust, embarrassment, and intuition in people with and without neuropsychiatric illness.

This reviewer, however, was somewhat surprised by important foci of human thought and emotion that were not considered, such as music, art, poetry, storytelling, and religion/spirituality. These uniquely human preoccupations would also seem worthy probes to expose the “nature of the human brain.” In the totality of their deliberations, there seems to be an imbalance between what is conventionally considered the “neuro” at the expense of the “psych.” Notwithstanding this notion, the volume is a compact (168 pages of text, 61 pages of references), captivating, and current update of vital scientific advances that reflect upon the uniqueness of the human brain, mind, and condition. I highly recommend this book to students and practitioners of neurology, psychiatry, and neuropsychiatry as well as to others interested in understanding the unique nature of the remarkable human brain.