For those people who have no other means of communication, sniffing could provide liberation
To suffer from locked-in syndrome—to be mentally alert but physically paralysed—is one of the worst fates imaginable. Noam Sobel of the Weizmann Institute, in Israel, may have found a way to make this fate slightly more bearable.
He starts from the observation that even those who are otherwise paralysed can sniff. Sniffing is regulated by the soft palate, a flap of tissue in the back of the throat that directs the flow of air through the mouth and nose. The soft palate is controlled by cranial nerves—in other words, nerves that do not pass through the spinal cord. So spinal damage, a common cause of paralysis, does not affect these nerves. Nor does brain damage, unless it is to the exact part of the brain that controls the soft palate.
Dr Sobel and his team then developed a system for measuring changes in air flow caused by sniffing. It consists of a narrow tube that rests on the operator’s nose. This is connected to a sensor that picks up changes in pressure and translates them into electrical signals. These signals can then be used to get machines to do what the operator wants them to do. At least, that is the theory. All that is required is for the operator to work out how to sniff appropriately.
First, Dr Sobel’s team rigged up the device to allow people who suffer from locked-in syndrome to communicate, by dictating text onto a computer screen using coded patterns of sniffing. They worked with patients at Levinstein Rehabilitation Hospital in Ra’anana, a suburb of Tel Aviv. Their first volunteer, a 51-year-old woman, had been locked in for seven months. Within three weeks she was able to write a letter to her family.
Next, the team linked their system to an electric wheelchair. They found that as little as 15 minutes of practice was enough to give an individual complete control of the machine. Two inward sniffs move it forward. Two outward ones put it into reverse. An outward followed by an inward turns it right, and an inward followed by an outward turns it left.
Sniffing may have applications for the healthy, as well as the paralysed. It is faster than pressing a mouse button. Dr Sobel’s team has therefore built a version of the device for video gaming. If that catches on, arcades may soon sound as if everyone in them should be tucked up in bed.
