The Mind's Eye is about how our "mind's eye" - that mysterious theatre within, upon which we stage our private visual experience - works, and what goes wrong when it doesn't. But how to separate the mind's eye from the distracting input from the actual eye? Oliver Sacks is our greatest chronicler of people with unusual neurological and sensory disabilities and experiences, and the remarkable adaptations they people have made. Now, sadly, we learn that Sacks has begun to go blind due to eye cancer. The Mind's Eye includes his brilliant, poignant observations of this process, his terror and grief, culminating in his awe-inspiring, resilient use of that blindness to begin to better "dissect" out the mind's eye, now that his is no longer pounded by visual input from without.
Sacks has been writing about the adaptive capacities of the brain long before the brain's "neuroplasticity" - its ability to change its structure and function in response to experience - was generally appreciated. In his 1995 volume An Anthropologist on Mars, he observed that his subjects, in response to neurological illness, seemed to "reach out to life" and reorganize because "of the brain's remarkable plasticity." His writing at that time was generally about how understanding of plasticity might be used to compensate for, or accommodate to, these conditions, as opposed to "cure" certain brain disorders, something that wasn't even considered a possibility except in a few renegade quarters as late as the mid-1990s.
The book begins with stories about people with unusual vision problems, or adaptations. A musician who loses the ability to recognize objects and sight-read develops a remarkable musical memory, so she no longer needs the written music.
A Man of Letters describes how Canadian novelist Howard Engel one day woke unable to recognize words in his morning newspaper (which now appeared to be written in a unfamiliar language), because of a stroke that rendered him alexic and how he went on reorganize his brain to read again. Engel learned to trace words with his fingers, and thus use motor memory to take words in. In essence, he learned "reading by writing," He also learned to "read" by moving his tongue, in a "metamodal sensory-motor alchemy." What Engel did was develop a neuroplastic compensation, strengthening a motor circuit in his brain that developed for another purpose.
Sometimes "compensations" can lead to jaw-dropping improvements, simply by strengthening circuits, as in the case of a woman who, in response to becoming paralyzed, learned to memorize the entire New York Times crossword - its configuration, all its clues - in a single intense inspection, and then solve it at her leisure, without effort, later in the day.
In other cases, Sacks's subjects use their plasticity to rise to a "normal" level of functioning. Stereo Sue is the story of Sue Barry, a scientist who grew up with no depth vision. She gained it in adulthood, with training, even though most believed the adult brain was not plastic enough to change. This result is a neuroplastic cure because she, rather than learning to "accommodate" or "compensate" for her problem, actually fixed it with the help of a developmental optometrist.
Apart from Barry herself (who has written a wonderful book about her cure, Fixing My Gaze), Sacks, as one who, since childhood, was passionately interested in stereoscopic vision and playing with building stereoscopes (he is a member of the New York Stereoscopic Society), is remarkably able to explain the difference between looking at a scene with one eye or two, and how the perception of depth deepens our appreciation of life.
In Face-Blind, we learn that Sacks, not unlike his most famous case, The Man who Mistook his Wife for a Hat, has had a lifelong brain condition rendering him unable to recognize faces. His patient, Dr. P., had a stroke, affecting the fusiform face area of the brain, giving rise to a condition called prosopagnosia. Sacks has a congenital version of this condition which has never improved, despite "a lifetime of trying to compensate," showing, perhaps the limits to plasticity (or perhaps the limits of compensation.) After many years, he's been able to recognize his closest friends, Eric Korn and Jonathan Miller, but usually by identifying individual features just off the face, such as Korn's thick spectacles or Miller's mop of red hair.