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However, recent studies from Schiff’s lab and others have shown that at least some of these seemingly unaware patients have a startlingly high level of brain activity, mentally reacting to stories and commands much as a healthy person would. Schiff and others who study minimally conscious patients are careful to distinguish them from patients such as Terri Schiavo, who received nationwide media attention in 2005. Schiavo was in a vegetative state, which she entered after lack of oxygen led to widespread brain-cell death. When a brain injury is caused by trauma, on the other hand, the damage is often limited to the nerve fibers that connect different parts of the brain, and some neural circuits may remain intact. Among these patients, the new imaging studies are revealing a surprising potential for some restoration of normal brain activity.

The findings offer hope for a group of people largely given up for lost by the medical community. Schiff and others are working to piece together the structural or functional changes that enable some MCS patients to awaken; eventually, the researchers hope to design treatments that can spur those changes in others. At the same time, they are opening a window on a hidden world. “Consciousness is a subjective, first-person experience,” says Laureys. “It is very tricky to conclude the absence of consciousness based on the absence of response at the bedside. There might be some inner world that we have no way to assess.”

Mental Tennis

In 1998, Joy Hirsch, a neuroscientist at the Columbia University Medical Center in New York City, paved the way for studies that use functional MRI (fMRI) to assess impaired consciousness. By measuring blood flow in the brain, fMRI can pinpoint regions that are active when, for example, a person is feeling anger or working on an abstract problem. Hirsch wanted a way to locate–and thus protect–the language area in babies who needed brain surgery. While most previous fMRI studies had required volunteers to perform specific tasks, such as reading or speaking, to activate the relevant parts of the brain, Hirsch found that just reading a story to the babies could stimulate the region involved in speech. It became obvious, she says, that the same technique could be used to test cognitive function in minimally conscious patients.

Aided by further improvements in imaging technology, in 2005 Hirsch and Schiff used fMRI to examine how two minimally conscious patients responded to stories told by friends and family members. The results were similar to those seen in healthy volunteers. The stories triggered activity in the language centers and other areas of the brain, suggesting that certain clusters of neurons remained intact and functioning. When a patient listened to his sister tell stories about their childhood, for example, parts of his visual system lit up, suggesting that he might be imagining those scenes.

The findings sparked intense interest among neurologists, but without direct reports from the subjects themselves, it was difficult to judge exactly what the patients were experiencing. Were they trapped in a lonely mental prison, aware of the world outside but unable to respond to it? Did they experience only isolated moments of awareness? Or was the brain activity simply a sort of cognitive reflex, triggered by a familiar voice and a few evocative words or names?

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Tagged: Biomedicine

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