Magazine article Science News

Breathtaking Science: Biologists Home in on the Brain Area That Drives Respiration

Magazine article Science News

Breathtaking Science: Biologists Home in on the Brain Area That Drives Respiration

Article excerpt

Nearly 2,400 years ago in a treatise aptly titled "On Breath," Aristotle posed a question that continues to captivate scientists today: "How can we account for the maintenance of the breath inherent in us, and for its increase?" In a suburb just outside Washington, D.C., Jeffrey C. Smith shows just how close modern researchers are to answering that question. With the aid of a powerful microscope, a computer monitor, a loudspeaker, and an array of other devices, he and a colleague use a minuscule electrode to listen in on the electrical activity of a paper-thin disc of living brain tissue. Every few seconds, the speaker crackles with sound.

That recurring noise is compelling evidence that biologists have finally identified what French physiologist Jean Pierre Marie Flourens more than a century ago called the noeud vital--the vital node. It's the source of a body's natural breathing rhythm.

Over the past decade, Smith and other neuroscientists have homed in on this rhythm-generating kernel of nerve cells. They've located it within a well-defined region of the brainstem, the part of the brain that sits at the top of the spinal cord and controls most of the body's automatic functions. This brainstem area, called the pre-Botzinger complex, appears to drive both the normal, quiet breathing pattern and more complicated breathing actions such as sighs and gasps.

"We're very far along the road of solving the basic problem of how we breathe," says Smith, who works at the National Institute of Neurological Disorders and Stroke in Bethesda, Md. That solution is of more than academic interest. Understanding how the brain controls breathing could suggest new ways to prevent sudden infant death syndrome (SIDS), point toward safer anesthetics, and lead to better treatments for respiratory conditions such as sleep apnea, in which people have difficulty breathing while asleep. "There's considerable clinical relevance," says Smith.

THE VITAL NODE With two treatises on the topic, Aristotle was among the first to record his thoughts on the role of breathing. "A few of the earlier natural philosophers have dealt with respiration; some of them have offered no explanation why this phenomenon occurs in living creatures; other have discussed it without much insight, and with insufficient experience of the facts," he dismissively noted. Aristotle, of course, had his own theory. He argued that breathing cools the body heat generated by the "fiery nature of the soul which exists in the heart."

It was another 2,000 years before scientists began to recognize that breathing's core function is to draw in oxygen from the air and expel carbon dioxide. Although people can hold their breaths for a while and sometimes exert great control over breathing, the process usually is on autopilot. And for good reason. "From birth until death, you can't go too long without breathing," Jack Feldman of the University of California, Los Angeles wryly noted in a lecture at the Society for Neuroscience meeting in Orlando last November.

A person's heart can beat on its own, but it takes brainpower to drive even the automatic inhaling and exhaling of air. Galen, a Greek physician who lived a few generations after Aristotle, may have been the first to realize that. He noted that gladiators and animals could usually still breathe if injured below the neck but sometimes stopped breathing immediately when suffering neck and head injuries.

That observation points to the brain as the breathing center, but it doesn't indicate a specific part of the brain. When investigators in the 18th century showed that rabbits continue to breathe after their cerebrum and cerebellum are removed, researchers began to concentrate on the brainstem. In the 1840s, Flourens narrowed the field's focus to a specific brainstem region within an area called the medulla. Lesions in this area, his noeud vital, stopped respiration in animals. …

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