Recovering Consciousness

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In late September, a team of European neuroscientists (people who study the nervous system) reported that a patient who had been in a persistent vegetative state (PVS) for 15 years showed signs of consciousness after receiving a new nerve-stimulation therapy. The patient, a 35-year-old man who suffered severe brain injuries in a car accident, regained a level of consciousness once thought impossible. This pioneering treatment challenges the widely accepted medical view that people who have been in a persistent vegetative state for a year or more can never recover. The scientists suggest that innovative treatment can bring about changes even in the most severe cases of PVS. The results of the treatment were published in the journal Current Biology.

A persistent vegetative state is a rare but serious type of coma. PVS is caused by widespread damage to areas of the brain’s cerebral cortex and thalamus. These structures govern awareness of the self and its surroundings. The damage can result from head injury, stroke, or a lack of oxygen caused by drowning or cardiac arrest (heartbeat stoppage). People in a persistent vegetative state may have their eyes open, but they are not awake. The body’s automatic functions—such as breathing and heartbeat—continue even though the person is unconscious. However, a PVS patient cannot think, talk, see, hear, feel, eat, move voluntarily, or respond to other people.

The pioneering new therapy was developed by focusing on the vagus nerve, one of the 12 pairs of cranial nerves that connect directly to the brain. The vagus nerve connects the brain to almost all the vital organs in the body. It is also linked directly to two regions of the brain that scientists know play roles in alertness and consciousness. The scientists hypothesized that electrical stimulation of the vagus nerve may affect consciousness in PVS patients. They implanted a small electrical device in the patient’s neck. After one month of vagus nerve stimulation, the patient had achieved a level of minimal consciousness, and a dramatic improvement in brain activity.

The scientists now plan to conduct broader studies involving electrical stimulation of the vagus nerve. They hope to develop effective therapies to restore more PVS patients to consciousness. The research may also help scientists better understand how consciousness itself arises from the cells and structure of the brain. Understanding how the human conscious mind develops from the nervous system is considered so difficult that scientists have labeled it the “hard problem” of the mind.

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Image: Electroencephalograph (EEG) images show an increase of activity across the brain, as evidenced by the yellow and orange colors, following vagus nerve stimulation (VNS). Credit: © Martina Corazzol, Guillaume Lio, Arthur Lefevre, Gianluca Deiana, Laurence Tell, Nathalie André-Obadia, Pierre Bourdillon, Marc Guenot, Michel Desmurget, Jacques Luauté, Angela Sirigu

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