Another way of seeing

“She could recognize nothing in the ordinary way,” begins neurologist and author Oliver Sacks, launching into one of the quirky patient narratives that have made him one of the iconic science communicators of his time.

Speaking recently at the American Museum of Natural History, the Columbia University professor and clinician described the case of a thriving concert pianist who developed a disorder that turned her musically blind. One day, she found her sheet music suddenly, inexplicably, unintelligible. This problem began to seep, terrifyingly, into her everyday life, also leaving her unable to recognize objects and faces.

But on one occasion, Sacks visited the pianist’s apartment, and found it striking: “Everything was classified in terms of color,” he said. Her problems with recognition had made way for an acute sensitivity to color, which she used to classify and navigate the world.

Writing about such people – who develop and then adapt to striking disorders of perception – has made Oliver Sacks famous. He does not seem to enjoy the status. “I am distressingly visible,” said Sacks, speaking from a spot lit podium before a rapt museum audience of 900 on October 17.

Perceptive disorders are characterized by the brain’s inability to process the signals we receive via the general senses of sight, touch, and hearing. Sacks, the author of ten books about neuroscience – most famously Awakenings, which became an Academy Award-nominated film in 1990 – posits that though often difficult to pinpoint, these disorders are unexpectedly common and deserve greater medical recognition. He described agnosia: a kind of disjointedness in the brain which results in a multitude of perceptive problems, including the visual ‘face-blindness,’ which is an inability to recognize people. “Somewhere between two and three percent of the population cannot recognize faces – that amounts to five or seven million people,” Sacks said.

Face-blindness is a problem for Sacks, too. “I often apologize to a large, bearded clumsy man moving towards me, because I am afraid he is going to walk into me,” he explained, “and then I realize I’m looking at a mirror.” Blindness in his right eye has also destroyed his three-dimensional vision, turning the world painfully, mysteriously flat. Curiosity about his own and other perceptive disorders drives his urge to understand the neurological roots of perception.

Perceptive disorders have deep, twisted roots in the cortex – an undulating sheet of grey matter that makes up the surface of the brain. It is the powerhouse of our ‘higher functions’: the senses, motor activity, and finally, association, which is the function governing perception.

Simply, ‘perception’ is created by mentally processing the visual, tactile and auditory messages we receive from the environments we are in; an activity which happens fluidly in a healthy cortex. Robert Shapley, a neurologist from New York University’s Center for Neural Science, explains that normally, the cortex maps the external world by interpreting information, to tell us, in the case of visual signals for example, “what that map means, about space, shape and surface properties.” Perception is thus altered by cortical damage due to several causes, from head injury to wayward genetics, strokes, toxins or tumors.

“The cortex has multiple stages of processing,” Shapley explains, “it’s like an oligarchy of processing.” The type of damage, and the stage of processing at which interference occurs in this delicate system, determine the intensity of the disorder.

The sensitivity of the brain’s cortex is manifest in the range and complexity of perceptive disorders, which are often so fantastical that they are mistaken for dementia. Sacks has documented various forms of agnosia in patients: a complete loss of speech, an inability to judge where things are in a room, and hallucinations that run before the eyes like uncontrollable flashcards. Some of his patients report finding certain familiarity in the faces of people they have never met, and seeing in place of an actual object, an imagined other, conjured entirely by the brain. Each of these is testimony to the remarkable creativity of the human mind – and the terrible unease it can create for those with alternative perception.

“No one talked about dyslexia a few years ago. But now there are forms of teaching that make life much easier for [dyslexics],” Sacks said, emphasizing the importance of recognizing, appreciating, and treating perceptive disorders – however bizarre and hard to navigate.

Addressing his own visual problems, Sacks shrugged, saying “For me, things remain as flat as a playing card. Except in dreams. And except, I will admit, when I smoke a bit of pot.”