Questions Answered With the Pupils of Your Eyes

Aug. 5, 2013 — Patients who are otherwise
completely unable to communicate can answer
yes or no questions within seconds with the
help of a simple system -- consisting of just a
laptop and camera -- that measures nothing
but the size of their pupils. The tool, described
and demonstrated in Current Biology , a Cell
Press publication, on August 5 takes advantage
of changes in pupil size that naturally occur
when people do mental arithmetic.

It requires
no specialized equipment or training at all.
The new pupil response system might not only
help those who are severely motor-impaired
communicate, but might also be extended to
assessing the mental state of patients whose
state of consciousness is unclear, the
researchers say.

"It is remarkable that a physiological system as
simple as the pupil has such a rich repertoire
of responses that it can be used for a task as
complex as communication," says Wolfgang
Einhäuser of Philipps-Universität Marburg in
Germany.

The researchers asked healthy people to solve
a math problem only when the correct answer
to a yes or no question was shown to them on
a screen. The mental load associated with
solving that problem caused an automatic
increase in pupil size, which the researchers
showed they could measure and translate into
an accurate answer to questions like "Are you
20 years old?"

They then tested out their pupil response
algorithm on seven "typical" locked-in patients
who had suffered brain damage following a
stroke. In many cases, they were able to
discern an answer based on pupil size alone.

"We find it remarkable that the system worked
almost perfectly in all healthy observers and
then could be transferred directly from them
to the patients, with no need for training or
parameter adjustment," Einhäuser says.
While the system could still use improvement
in terms of speed and accuracy, those are
technical hurdles Einhäuser is confident they
can readily overcome.

Their measures of pupil
response could already make an important
difference for those who need it most.
"For patients with altered state of
consciousness -- those who are in a coma or
other unresponsive state -- any communication
is a big step forward," he says.

Story Source:

The above story is based on materials provided
by Cell Press, via EurekAlert!, a service of
AAAS.
Note: Materials may be edited for content and
length. For further information, please contact
the source cited above.
And ( science daily magzine ).
Journal Reference:

1. Josef Stoll, Camille Chatelle, Olivia Carter,
Christof Koch, Steven Laureys, Wolfgang
Einhäuser. Pupil responses allow
communication in locked-in syndrome
patients. Current Biology, 2013; 23 (15): R647
DOI: 10.1016/j.cub.2013.06.011