Until recently, few neurologists besides Plum were interested in learning more. The consensus was that semiconscious brains do not heal, especially not months or years after an injury, so research and aggressive treatment were futile. But the very first vegetative patient Schiff ever saw, during his first month as a resident at New York Hospital in 1993, told a different story.
This woman had had a stroke more than six months earlier. When Schiff examined her, he found no sign of consciousness, just as expected. Three years later, on a visit to a local rehabilitation center, he ran into his former patient again. Not only was she awake, but she spoke to him. “I was shocked,” he says now. “I remember the visceral feeling of having seen somebody come back from the dead. It seemed truly surreal.”
Around the same time, Schiff heard about a female patient who had been in a vegetative state for nearly 20 years but sometimes blurted out a word, usually obscene. His first thought was that she could not possibly be vegetative. He and Plum, who had become his mentor, arranged for her to be part of a study using positron emission tomography, better known as a PET scan. This technique uses radioactive markers to map the brain’s sugar metabolism—and, by implication, the speed at which neurons are firing.
When Schiff and Plum got this patient’s scans back, they were confused. The PET scan looked blank. Her injured brain was functioning at such a low level that the normal rich glow of activity was barely a glimmer. When the researchers recalibrated the display screen, though, they could see tiny blobs of neural action in brain regions specialized for speech. Consciousness requires connectivity, and her vegetative brain was mostly disconnected. Nevertheless, this one isolated loop remained hooked up and active. Amid her scorched neural landscape, it spat out an occasional word, without meaning or conscious will.
The following year, 1997, another patient brought Schiff to the JFK Johnson Rehabilitation Institute in Edison, New Jersey, where he met Giacino. They made a good team. Schiff was a neuroscientist, probing the nuts and bolts of the brain; Giacino was a diagnostic master, devising better ways to evaluate semiconscious patients. With the support of Joseph Fins, chief of the department of medical ethics at Weill Cornell, who articulated the ethical arguments for why these patients must be studied and treated, they used PET to look at four more people in vegetative states. Metabolically, all the brains were limping along, underactive and underaroused. Yet each patient’s pattern was idiosyncratic, showing unique clusters of remnant neural activity. “People look at these patients and say, ‘They’re all the same; they don’t respond; their brain doesn’t work,’ ” Giacino says. “This was a beautiful illustration of how dramatic the differences are.”
For their next act, the two researchers turned to another mystery, the much larger number of semiconscious brain-injured patients who are severely disabled but not truly vegetative. (In the United States, these are estimated at 280,000 cases versus 35,000 patients in the vegetative state.) These people are not merely awake but also partly aware. In them, consciousness is neither on nor off; it is unstable, emerging and fading “like the smile on the Cheshire cat,” Schiff says. On good days they might follow people or objects with their eyes, nod, laugh, even say a word. On bad days they do not react at all.
Schiff and Giacino, working with Columbia University neuroimaging expert Joy Hirsch and graduate student Diana Rodriguez-Moreno, started probing these unpredictable brains in 2001 using functional magnetic resonance imaging (fMRI), which tracks the minute changes in blood oxygenation that correspond to neural activity. They reasoned that some regulatory mechanism of the brain must be oscillating up and down, creating these wide swings in awareness, and fMRI might clarify what it was. In 2002 a group of neurologists led by Giacino formally chose the term “minimally conscious” to describe these patients.
One subject who fell into this category was a man who had been beaten and kicked in the head during a robbery several years back. About 30 percent of the time, he was able to follow instructions, indicating “yes” or “no” by looking at a card, but he only rarely spoke a word or two. Most of the time, he kept his eyes closed. While he was undergoing fMRI, the team played a recording of his mother’s voice. They expected to see isolated flares of activity in simple language-processing regions. Instead, the whole network of cortical regions specialized for hearing and language comprehension fired up, just as in a healthy brain. “It was stunning,” Giacino says. The patient’s visual cortex was buzzing too, as if the sound of his mother’s voice had conjured up her face. A second subject responded in much the same way.
In some types of brain injury, people eventually regain full consciousness, with normal awareness and intellect, but are trapped in an unresponsive body; they are said to be “locked in.” But the two patients in this study clearly did not rise to that level. As part of the experiment, the team played recordings of speech that had been reversed. In healthy subjects, language-processing regions become more active when they hear such backward speech, working hard to interpret strange-sounding words. These patients’ brains reached only the earliest stages of response, as if they could not engage enough to ask, “Hey, what’s that?” The difference between a vegetative and a minimally conscious brain was looking like a question of how much brain wiring remained intact and, more important, still able to pass along a signal. Neurologist Steven Laureys of the University of Liège in Belgium, who would later collaborate with Schiff and Giacino, showed that same year, 2002, that in vegetative patients, mild electric shocks activated basic sense-perception regions but not the higher-level information processing networks (pdf) that the minimally conscious patients could access.
The brain scans of the robbery victim had revealed enough connectivity and enough bandwidth to register and process a human voice. What the patient could not do was maintain his awareness. Since medical school, Schiff had believed that a technique called deep brain stimulation might help patients who have viable, networked cortical tissue but inconsistent awareness. In deep brain stimulation, electrodes are permanently installed in the brain, like a neural pacemaker. (It is most often used to help people with Parkinson’s disease regain control over their limbs.) Such stimulation had not worked very well in a trial conducted on vegetative patients in the 1980s by the medical device company Medtronic. But Schiff, who had been mapping the pathways of consciousness, was convinced that Medtronic had picked the wrong patients—those who were catastrophically injured and beyond help—and had put the electrodes in the wrong place.