Saturday, June 28, 2008

Annals of Medicine - Atul Gawande

Atul Gawande is a Boston-based surgeon at the Brigham and Women's hospital and a staff writer for The New Yorker magazine. His excellent essays on the practice of medicine have appeared in the magazine for several years and they have been the basis of his two published collections titled "Complications: A Surgeon's Notes on an Imperfect Science" and "Better: A Surgeon's Notes on Performance".

Gawande's penchant for meticulous scientific examination of his own professon yields many useful insights (even for non-practitioners) and provides laypeople an unusually clear view of the "imperfect science" of diagnosis and cure and the human element that often makes it so. Gawande's writing is precise and uncluttered and he manages to explain complex topics with an admirable clarity of thought in very readable prose.

Gawande is one of the more recent in a line of accomplished physicians who have written insightfully about their vocation and provided a much needed empathetic transparency into the seemingly impersonal workings of the American system of sickness and health. Dr. Jerome Groopman, Oliver Sacks and Sherwin Nuland particularly come to mind as I think of doctors who have contributed tremendously to American medicine and letters. (Even outside of his writings on medicine, Nuland's memoir, "Lost in America" is one of my all-time favorites with an exceptionally touching portrait of a father-son relationship).

This week Gawande has an essay in the New Yorker titled "The Itch". In this piece he investigates this poorly understood sensation, its scientific source and its function. In explaining the biological provenance of uncontrollable itching, Gawande surveys the current scientific understanding of "Perception" and this is a fascinating part of the essay.

Here are some excerpts:

Our assumption had been that the sensory data we receive from our eyes, ears, nose, fingers, and so on contain all the information that we need for perception, and that perception must work something like a radio. It’s hard to conceive that a Boston Symphony Orchestra concert is in a radio wave. But it is. So you might think that it’sthe same with the signals we receive—that if you hooked up someone’s nerves to a monitor you could watch what the person is experiencing as if it were a television show.

Yet, as scientists set about analyzing the signals, they found them to be radically impoverished. Suppose someone is viewing a tree in a clearing. Given simply the transmissions along the optic nerve from the light entering the eye, one would not be able to reconstruct the three-dimensionality, or the distance, or the detail of thebark—attributes that we perceive instantly.
The images in our mind are extraordinarily rich. We can tell if something is liquid or solid, heavy or light, dead or alive. But the information we work from is poor—a distorted, two-dimensional transmission with entire spots missing. So the mind fills in most of the picture. You can get a sense of this from brain-anatomy studies. If visual sensations were primarily received rather than constructed by the brain, you’d expect that most of the fibres going to the brain’s primary visual cortex would come from the retina. Instead, scientists have found that only twenty per cent do; eighty per cent come downward from regions of the brain governing functions like memory. Richard Gregory, a prominent British neuropsychologist, estimates that visual perception is more than ninety per cent memory and less than ten per cent sensory nerve signals.
The account of perception that’s starting to emerge is what we might call the “brain’s best guess” theory of perception: perception is the brain’s best guess about what is happening in the outside world. The mind integrates scattered, weak, rudimentary signals from a variety of sensory channels, information from past experiences, and hard-wired processes, and produces a sensory experience full of brain-provided color, sound, texture, and meaning. We see a friendly yellow Labrador bounding behind a picket fence not because that is the transmission we receive but because this is the perception our weaver-brain assembles as its best hypothesis of what is
out there from the slivers of information we get. Perception is inference.
Update: In today's New York Times (July 4th, 2008) Dr. Atul Gawande answers questions about "The Itch"that some readers had after reading the original article.

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