AFTER STROKE, BRAIN LEARNS TO SEE AGAIN

UNIVERSITY OF ROCHESTERrightOriginal Study

Posted by Tom Rickey-Rochester on May 1, 2009

Once thought irreversible, vision loss sometimes associated with stroke may be treatable. 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.

Such rigorous visual retraining is not common for people who suffer blindness after a stroke. That’s in contrast to other consequences of stroke, such as speech or movement difficulties, where rehabilitation is common and successful.

“We were very surprised when we saw the results from our first patients,” says Krystel Huxlin, the neuroscientist and associate professor who led the study of seven patients at the University of Rochester’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 a remarkable capacity for “plasticity” in damaged, adult brains. It 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.

IMPOSSIBLE TO READ OR DRIVE

Huxlin studied seven people who had suffered a stroke that damaged an area of the brain known as the primary visual cortex or V1, which serves as the gateway to the rest of the brain for all the visual information that comes through our eyes. V1 passes visual information along to dozens of other brain areas, which process and make sense of the information, ultimately allowing us to see.

Patients with damage to the primary visual cortex have severely impaired vision–they typically have a difficult or impossible time reading, driving, or getting out to do ordinary chores like grocery shopping. Patients may walk into walls, oftentimes cannot navigate stores without bumping into goods or other people, and they may be completely unaware of cars on the road coming toward them from the left or right.
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. Everything right or left of center, depending on the side of the stroke, might be gray or dark, for instance.

Despite the stroke, the patients’ eyes are taking in visual information. It’s just that the damaged brain cannot make sense of it to create vision.

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 question is whether we can we recruit other, healthy regions of the brain to benefit the person’s vision. Can we train those brain regions so hard and stimulate the brain to such a degree that this visual information is brought to consciousness, so the person is aware of what they’re seeing?” says Huxlin.

30 MINUTES A DAY

Huxlin began the study with seven people, four women and three men, ranging from their 30s to their 80s, who had had a stroke anywhere from eight to 40 months before the experiment began. All had suffered substantial damage to the primary visual cortex. The funding to support the work came from Research to Prevent Blindness, the Pfeiffer Foundation, the Schmitt Foundation, and the National Eye Institute.

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.

The patients in the study did about 300 tests at a time, which translated roughly to sitting in front of a computer for 15 to 30 minutes once or twice a day, every day, for nine to 18 months. It’s an exhausting task, especially for someone whose brain is working extra-hard to accomplish it. The University of Rochester has filed a patent on the technology.

“Basically, it’s exercising the visual part of the brain every day,” explains Huxlin. “It’s very hard work, very grueling. By forcing patients to choose, you’re helping the brain redevelop.”

The findings are reported in the Journal of Neuroscience.