In the 40 years since he published his first book, neurologist Oliver Sacks has introduced thousands of readers to various neurological issues by sharing his patients' fascinating case histories. These include, most famously, the man suffering from severe agnosia - an inability to recognize even familiar objects - who mistook his wife for a hat in the 1985 book of that title.
"The Mind's Eye," his 11th book, returns to the subject of visual perception, exploring the stereoscopy that enables us to see in three dimensions and the role of mental imagery in thinking and vision.
Sacks is that rare doctor willing to make house calls and get to know his patients outside clinical settings. In "Sight Reading," he sees concert pianist Lilian Kallir, who has lost her ability to read musical notation but not her ability to write (alexia sine agraphia), in her apartment, in his home and on visits to her supermarket to assess how she manages. After an appointment in his office, Sacks reports, Lilian grabs the wrong bag. Realizing her error, she returns, declaring with charm, "I am the woman who mistook the doctor's bag for her handbag."
Alexia is a degenerative disease that shows up on MRIs as shrinkage of visual areas of the brain. There doesn't seem to be much that neurologists can offer most patients with degenerative brain disease, beyond the ability to pinpoint the problem with increasingly sophisticated imaging devices like PET scans and functional MRIs.
Sacks, however, is interested in the enormous plasticity of the brain, an adaptability that leads to workarounds that keep his patients functioning. A novelist with alexia sine agraphia, for example, continues the visualization necessary for writing by tracing letters in the air with his tongue, of all things. Another patient, who suffers a massive cerebral hemorrhage that leaves her semi-paralyzed and unable to speak, manages, through therapy that spans years, to regain some quality of life. Sacks comments that "in the past few decades neuroscience has confirmed that the brain has more powers of repair and regeneration than was once believed."
The brain's plasticity has helped Sacks cope with his own congenital prosopagnosia, an inherited difficulty recognizing faces and places - a condition he says is shared by perhaps 2 percent of the population, including his brother, anthropologist Jane Goodall and artist Chuck Close, among others.
Sacks elicits instruction from his own personal experiences. He draws on excerpts from his "melanoma journals" to describe his struggles with an ocular melanoma diagnosed in 2005. These convey both his panic and his sometimes overly detailed observations of the effects of each stage of radiation and laser treatment, including, finally, a hemorrhage that left him with disorientingly flat, monocular vision - a dismaying handicap for an enthusiastic member of the New York Stereoscopic Society.
With its heavy use of long footnotes and forays into complex questions about "the brain-mind problem and the nature of consciousness," "The Mind's Eye" is less focused on vivid case histories than Sacks' most engaging works. But in one of the more resonant images of the book, Sacks likens the brain to "an orchestra that conducts itself, with an ever-changing score and repertoire." It's an orchestra whose sometimes off-key performances Sacks has spent decades recording with high fidelity, resulting in a remarkable body of work.