Locked-in Syndrome is when a person is conscious, but paralyzed and unable to communicate. The condition was made famous by Jean-Dominique Bauby, who suffered a massive stroke and was unable to move except for blinking his left eye. Bauby dictated his memoir, The Diving Bell and the Butterfly — which was made into an Oscar-nominated film — by blinking.
But many people suffering from Locked-In Syndrome cannot even control their blinking. To help these patients communicate, researchers at Philipps-Universitat Marburg in Germany came up with an eye-tracking system system that uses a digital camera with a laptop to monitor the sizes of a person’s pupils. The researchers found that it was possible to tell when someone was responding to a question by how much the pupil dilated, reflecting the mental effort they were making.
For the experiment, the researchers started with a group of healthy people. Each participant sat before a camera and a computer display and were asked to answer a yes or no question using their brain power instead of their voices. Here’s how it worked: A question such as “Is your age 20?” displayed on the screen. Five seconds later, a computer voice read out the answer “yes” and displayed a math problem, in this instance multiplying 24 and 57. If the participant’s age was indeed 20, she would solve the math problem. However, if 20 was not her age, she did nothing. A few seconds later, the computer voice said “no” and the screen displayed a second math problem, multiplying 29 and 49. The participant would then solve this problem in order to answer “no.” The experiment was repeated with the answers in the reverse order.
After trying this out several times on half a dozen people, patterns emerged. Pupils dilated in a specific pattern depending on which answer was correct. That allowed the scientists to write a computer program interpreting the pupil’s changes, essentially coding for “yes” and “no” answers. The program can run on any laptop, linked to an ordinary digital camera.
The scientists then tested out their pupil-response algorithm on seven locked-in patients who had suffered brain damage following a stroke. The results showed that it was possible to get “yes” and “no” answers from the patients. That means that with a little fine-tuning, the algorithm could give these people a way to communicate — and even be a way of checking whether someone is conscious or not after severe brain damage, avoiding a misdiagnosis of brain death or vegetative states.
The experiment is in the latest issue of the journal Current Biology.
Credit: Current Biology, Stoll, et al.