May 11, 2009
Visual Training Can Teach the Brain to See Again after Stroke
Medical Center study gives new hope to those who suffer blindness after a stroke.
Richard Farrands, of Fulton, undergoes rigorous visual testing as part of a study that aims to improve the vision of patients who have had a stroke. Researcher Krystel Huxlin, (left) developed the computer system which exercises the brain, forcing it to develop to compensate for the damage caused by stroke. Patients who completed the study regained at least some of their vision, and some even were able to drive again.
By doing a set of vigorous visual exercises on a computer every day for several months, patients who had gone partially blind as a result of suffering a stroke were able to regain some vision, according to Medical Center scientists.
The results of the study were published in the April 1 issue of the Journal of Neuroscience.
Rehabilitation is common and successful for other effects of stroke, such as speech or movement difficulties, but visual retraining is not common.
“We were very surprised when we saw the results from our first patients,” said Krystel Huxlin, the neuroscientist and associate professor who led the study of seven patients at the University’s Eye Institute. “This is a type of brain damage that clinicians and scientists have long believed you simply can’t recover from. It’s devastating, and patients are usually sent home to somehow deal with it the best they can.”
The results are a cause for hope for patients with vision damage from stroke or other causes, says Huxlin. The work also shows that the brain can change a great deal in older adults and that some brain regions are capable of covering for other areas that have been damaged.
Huxlin studied seven people who have severely impaired vision after suffering a stroke that damaged an area of the brain known as the primary visual cortex. Depending on where in the brain the stroke occurred, most patients will be blind in one-quarter to one-half of their normal field of view.
Huxlin’s team sought to build on this “blindsight”—visual information, of which the patient is unaware, that still reaches the brain. A few past studies have shown promise for the idea of building on blindsight to improve a person’s vision.
The team focused on motion perception, since it’s an aspect of vision critical for most everyday tasks. The team’s aim was to see if the brain’s middle temporal region, which was healthy in the participants, could be stimulated so extensively that it could take on some of the tasks normally handled by the visual cortex.
The five participants who performed the training and completed the experiment had significantly improved vision. They were able to see in ways they weren’t able to before the experiment began. A few found the experiment life-changing—a couple of participants are driving again, for instance, or have gained the confidence to go shopping and exercise frequently.
To do the experiment, participants fix their gaze on a small black square in the middle of a computer screen; scientists use a sensitive eye tracker to make sure patients keep staring at the square.
Every few seconds, a group of about 100 small dots appears within a circle on the screen, somewhere in the person’s damaged visual field. The dots twinkle into existence, appear to move as a group either to the left or the right, then disappear after about one-half second. Then the patient has to choose whether the dots are moving left or right. A chime indicates whether he or she chose correctly, providing feedback that lets the brain know whether it made the right choice and speeding up learning.
“The patients can’t see the dots, but they’re aware that there is something happening that they can’t quite see. They might say, ‘I know that there’s something there, but I can’t make any sense of it,’” says Huxlin, who is also a faculty member in the Departments of Ophthalmology, Neurobiology and Anatomy, Brain and Cognitive Sciences, and in the Center for Visual Science.
But the brain is able to make some sense of it all. When forced to make a choice, patients typically start out with a success rate of around 50 percent by guessing. Over a period of days, weeks or months, that number goes to 80 or 90 percent, as the brain learns to “see” a new area. Patients eventually become aware of the dots and their movement.
As patients improve, researchers move the dots further and further into what was the patient’s blind area, as a way to challenge the brain, to coax it to see a new area.
“Basically, it’s exercising the visual part of the brain every day,” said Huxlin. “It’s very hard work, very grueling. By forcing patients to choose, you’re helping the brain re-develop.”
Working with Huxlin on the work were Tim Martin, a post doctoral research associate; Kristin Kelly, formerly a technical associate and now a medical student; former graduate student Meghan Riley; neuro-ophthalmologist Deborah Friedman; neurologist W. Scott Burgin; and Mary Hayhoe, formerly of the Department of Brain and Cognitive Sciences at the University of Rochester, and now at the University of Texas at Austin. Rochester has filed a patent on the technology.
The funding to support the work came from Research to Prevent Blindness, the Pfeiffer Foundation, the Schmitt Foundation, and the National Eye Institute.