In the field of neurology, Sacks says, the key word is “deficit.” In large part, neurologists have learned about the mind by studying the brains of patients who lack basic mental faculties. In 1861, for example, scientists identified the area of the brain that controls speech by studying patients who couldn’t form words. Later, the great psychologist Sigmund Freud argued that, in order to study patients who lacked perceptive abilities, scientists needed to study deficits in the mind—not necessarily problems with specific areas of the brain, but rather with the brain’s overall structure. Freud’s arguments led to the growth of “neuropsychology,” a field closely related to neurology.
In the introduction to Part One, Sacks begins by discussing deficit—not exactly a scientific theory or phenomenon (which can be proven and measured) so much as a paradigm or a way of conceiving of a host of different scientific phenomena. By using the concept of deficits, neurologists—scientists who study the nervous system—have a convenient way of organizing and classifying their ideas and observations, and indeed, Sacks will use the concept of a deficit to organize the case studies in the first quarter of his book.
For the most part, neurology and neuropsychology focus on deficits in the left hemisphere of the brain. One reason for this is that the left hemisphere is sometimes considered to be the more specialized, sophisticated half of the brain. Certain neurologists did explore mental problems caused by deficits in the right hemisphere, but the medical establishment often neglected such studies. Right-hemisphere deficits are often more difficult for doctors to understand, and yet right-hemisphere deficits are just as common as left-hemisphere deficits.
Here, we see how the specific paradigm (the framework of working assumptions or beliefs) of mental illness as deficit has resulted in a tangible bias in neurology. Because scientists are perhaps overly committed to the deficit paradigm, they neglect right-hemisphere diseases (partly because such diseases are much harder to conceive of as a deficit in a specific way).
Toward the end of his life, the great neuropsychologist A. R. Luria wrote a letter to Oliver Sacks, the author, in which he urged Sacks to research right-hemisphere disorders. Sack’s strategy for studying right-hemisphere disorders has been markedly different from that adopted by earlier neuropsychologists. Often, neuropsychologists have characterized disorders in terms of the precise deficit in the brain that causes the disorder. Sacks, however, will instead analyze brain disorders by studying both the physical deficits in the brain and also the holistic effect of the deficit on his subjects’ lives. Sacks offers a new way to conceive of mental disorders: mental disorders represent the mind’s attempts to “preserve identity in adverse circumstances.” In the first part of his book, Sacks will discuss cases of patients who lack a certain part of the mind, and who compensate for the absence. In taking such an approach, Sacks will challenge the conventional neurological wisdom.
A. R. Luria was an important figure in Oliver Sacks’s career; just as Sacks was starting out as a doctor, Luria acted as his mentor and adviser. Sacks lays out this section’s project: analyzing brain disorders that could be classified as types of deficits, but which, due to their right-hemisphere origins, have been largely neglected by the neurological community. Sacks also alludes to the important idea of equalization—in other words, the notion that patients with neurological impairments find ways of compensating for their problems and adapting to their new situations. This principle is important because it corrects for the tendency to conceive of mental illness as static and unchanging.