Saturday, November 9, 2013

TAU experiment finds awareness in ‘vegetative’ patients

An Israeli team has shown that the brains of individuals in a persistent vegetative state can react to the world outside their minds

Although individuals in a vegetative state are able to breathe, awaken, and sleep normally, they can’t communicate with others – and it’s been assumed that they have no awareness of what is going on around them. But several experiments by researchers at Tel Aviv University’s Sourasky Medical Center show that in some cases so-called “vegetables” indeed are aware of what is going on around them – and can respond, at least on an emotional level, to external stimuli. 

According to medical officials, as many as 40,000 patients In the US are in a persistent vegetative state (PVS), the medical term for those who have been unable to react to external stimuli for a year or more. Noted PVS sufferers include Karen Ann Quinlan, who was at the center of a famous 1976 “right to die” case in the US, Terry Schiavo, the subject of a long series of US court decisions on the same issue – and former Prime Minister Ariel Sharon, who has been a PVS patient since suffering a stroke on January 4, 2006.  

The experiments, conducted by Dr. Hagai Sharon and Dr. Yotam Pasternak of Sourasky (under the supervision of Prof. Talma Hendler, director of the center), examined the brain responses of four PVS patients, who were shown a series of photos of individuals they were unfamiliar with, along with images of friends, family, and of the patient him or herself.

Sharon and Pasternak gauged the reactions of the patients using an fMRI — a functional magnetic resonance imaging device that examines blood flow in the brain to detect areas of activity in real time. They compared the readings with those taken of healthy subjects who were given similar treatment.

Surprisingly, said Sharon, in both sets of subjects, an area of the brain responsible for the visual processing of faces was activated when the “familiar” pictures were shown. “In other words, the brains of those who were in a vegetative state were able to distinguish between different objects in the external world,” she said.

The experiment actually yielded two important findings, said Sharon; not only is it now known that the brains of individuals in vegetative states respond to external stimuli, but those brains are capable of complex environmental stimuli (such as distinguishing between known and unknown faces), similar to the process in a healthy brain.

While the response in PVS patients in the study showed that their brains were active, the question remains as to whether the responses are the result of an automatic brain process, or a conscious awareness of their surroundings. In order to answer that question, Sharon and Pasternak came up with an experiment that would require conscious mental activity, with an attempt by subjects to imagine a mental image of their parents. The healthy patients were able to do this without a problem, but at least one of the PVS subjects was able to do it as well after being asked to do so verbally, the team said. A second subject succeeded partially, according to the results indicated by the fMRI, and compared to the reactions of healthy patients, said Sharon.

Center Director Hendler said that “this is the first time such an experiment has been conducted with patients like these. It demonstrates that not only do they have at least some emotional awareness of their environment, but that they are able to create emotional activity with their internal brain processes, after prompting from an external source – similar to the process of daydreaming, etc. Beyond the enormous importance of these findings in understanding the condition of these patients,” added Hendler, “we hope that this disclosure will pave the way to new approaches to treatment and rehabilitation of these difficult to treat patients.”