A pair of monkeys were able to “see” and recognize individual letter shapes generated by arrays of electrodes implanted in their brains – without using their eyes. Previously, sight-restoring implants were placed in the retina, but these new implants were placed in the visual cortex. They achieved the highest resolution yet for such technology.

The research took place at the Netherlands Institute for Neuroscience (NIN). The scientists wanted to develop a way to restore sight for people whose optic nerves were damaged and couldn’t benefit from retina implants. The team, led by Pieter Roelfsema, created a brain implant made of needle-like electrodes 1.5 millimeters in length. They placed it on the animals’ visual cortex, partially restoring its sight.

The visual cortex is like a cinema screen in our skull, with each area on its surface mapping to the visual field. Placing a patch of electrodes on the surface that activate like pixels will make a person “see” whatever points get activated. For example, if an L-shaped pattern of electrodes in contact with the visual cortex is activated, they will see a pixelated L.