Electrical current through the brain jolts vision into sharper focus

A mild electrical current to a certain part of the brain has been found to affect how it processes visual information(Credit: Ken Teegardin/CC BY-SA 2.0)

If you find yourself struggling to focus on an object, there may one day be an alternative to reaching for your glasses or popping in your contact lenses. Scientists have found that by delivering a mild electrical current to a certain part of the brain they can affect how it processes visual information, leading not only to sharpened focus for the subject, but possibly a new understanding of our sense of sight as well.

Stimulating the brain with electrical currents has shown promise in a number of different areas of healthcare. These include treating psychological disorders, preventing migraine attacks, rehabilitating stroke victims and even helping us to learn from our mistakes. So for researchers at Vanderbilt University, adapting the technology to improve eyesight wasn't all that big of a leap.

"It's actually a very simple idea," says co-author Geoff Woodman, associate professor of psychology at Vanderbilt. "This kind of stimulation can improve cognitive processing in other brain areas, so if we stimulate the visual system, could we improve processing? Could we make someone's vision better – not at the level of the eye, like Lasik (laser treatment) or glasses, but directly at the level of the brain?"

Woodman and his team recruited 20 healthy subjects with normal or near-normal vision. The subjects were shown a pair of identical lines and asked to determine whether they were perfectly aligned or set apart. This particular test is said to be more sensitive than the conventional eye chart at your doctor's office, so the researchers say it allowed for more precise assessments of the subjects' vision.

Then a very mild electrical current was delivered to the visual cortex located at the back of the brain for around 20 minutes . The subjects then took the test again, with around 75 percent of the group displaying measurable improvement, with the benefits lasting as long as two hours.

The researchers played around with different versions of the experiment, testing out different intensity levels, current directions and placement of the electrodes. It was through this they determined that the electrodes needed to be placed specifically over the brain's visual cortex for the technique to work, rather than just providing stimulus anywhere in the brain.

Looking to assess just how big the vision enhancements were and whether the technique could actually make a difference in the real world, the researchers also had the subjects read a standard eye chart. They found vision improved by an average of one to two letters, but it was far from an even improvement across the board.

"We saw that those who came in with poorer vision, who might be on their way to needing glasses, had these big leaps, while others who came in with excellent vision showed no change," said lead author Robert Reinhart.

As for how this process of sharpening vision actually plays out inside the brain, the researchers have a couple of ideas. They say it could simply be that the current boosts visual signals and allows particular neurons to process them more quickly. But it is also possible that the current creates a white noise effect, where unnecessary information is drowned out and the brain can absorb the actual subject matter more easily.

The technique could provide scientists with a new way to probe the intricacies of human vision, though they do point out that further clinical testing is required before it is declared safe to use for the general public.

"Now we have a new tool that could be valuable for researchers investigating fundamental questions about how the visual system works," says Reinhart.

The research was published in the journal Current Biology.

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