Devices & Diagnostics, Hospitals

Could locked-in patients soon communicate without spelling like The Diving Bell and the Butterfly hero?

In The Diving Bell and the Butterfly, Jean-Dominique Bauby, who has locked-in syndrome, must listen […]

In The Diving Bell and the Butterfly, Jean-Dominique Bauby, who has locked-in syndrome, must listen to his nurse recite the letters of the alphabet and blink to the corresponding letter to spell out each of his responses. It’s a time-consuming and painstaking process that fills much of their days and causes fatigue, but it does allow for communication.

But scientists may have discovered an easier mode of conversation. And the device they use is surprisingly low tech: a simple bedside camera.

In the latest issue of Current Biology, a team of researchers from Germany, Belgium, Australia and the United States has found using a bedside camera to measure pupil size can help those communicating with a locked-in patient to discern responses for questions with two answers with varying success. Three of seven “typical” locked-in patients had results hovering just above the odds of chance they were rendered insignificant, while three others “were significantly different from chance at an individual level.”

The authors mentioned it could be used for this kind of communication with very little training on the part of the clinician, and that it could perhaps be used as a diagnostic to test consciousness. (Plus, if it works, it could save a lot of expense.)

From the report:

Our data provide proof-of-principle for pupil dilation as means of communication in severely motor-impaired patients. With no training and no parameter adjustment to the individual, up to 90% decoding performance was reached. Rather than utilizing the response to a decision as such, which could, for example, be confounded with the difficulty of the decision, our paradigm allows patients to actively control their pupil dilation by modulating their mental effort. Whether or not patients actually solve the problem posed is of little relevance. Rather, mental arithmetic provides one robust way (amongst many) to manipulate one’s pupil dilation, even if — as in the minimally conscious state patients — no active engagement in the task is otherwise apparent.

Typical brain-computer-interfaces either use invasive methods or EEG in combination with machine-learning techniques to measure neural activity. Besides the risk of the surgical procedure or the maintenance demands (for example, electrode cleaning), with few exceptions training with the individual is required. Pupil size controlled through mental effort offers an alternative path, reflecting (neuro-)physiological activity that is easy and inexpensive to measure in daily life, requiring nothing but a bedside camera. Furthermore, in cases of complete locked-in syndrome, approaches that require some residual volitional movements, such as sniffing or blinking, are by definition unsuitable. In contrast, our system may in principle be tested in patients in complete locked-in syndrome without training prior to an acute insult. Finally, the minimally conscious state data demonstrates our system’s potential usefulness as an additional diagnostic tool to assess a patient’s state of consciousness.

 

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