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29/01/2016

People with epilepsy help scientists decode brain signals nearly at speed of perception

Using electrodes implanted in the temporal lobes of awake epilepsy patients, scientists have decoded brain signals at nearly the speed of perception. Further, analysis of patients' neural responses to images of faces and houses - enabled the scientists to subsequently predict which images the patients were viewing.

The study involved seven epilepsy patients receiving care at Harborview Medical Center in Seattle. Each was experiencing epileptic seizures not relieved by medication, so had undergone brain surgery during which electrodes were temporarily implanted in their temporal lobes to try to locate the seizures' focal points.

"They were going to get the electrodes no matter what; we were just giving them additional tasks to do during their hospital stay while they are otherwise just waiting around," explained University of Washington  Medicine neurosurgeon Jeff Ojemann.

The subjects, watching a computer monitor, were shown a random sequence of pictures - brief (400 millisecond) flashes of images of human faces and houses, interspersed with blank grey screens. Their task was to watch for an image of an upside-down house.

The computational software analysed the subjects' brainwaves to determine which combination of electrode locations and signal types correlated best with what each subject actually saw.

Scientists were able to predict with 96 per cent accuracy whether and when (within 20 milliseconds) the subjects were seeing a house, a face or a gray screen.

University of Washington computational neuroscientist Rajesh Rao explained: "Clinically, you could think of our result as a proof of concept toward building a communication mechanism for patients who are paralysed or have had a stroke and are completely locked-in."