Scientists have enabled a completely blind Spanish woman to see basic shapes by placing an electrode array directly onto her visual cortex. This allowed the researchers to stimulate specific groups of neurons, resulting in the generation of crude images in the patient’s field of vision.
Reporting their findings in the Journal of Clinical Investigation, the study authors described how they inserted the implant into the brain of a 57-year-old volunteer who had been fully blind for 16 years. The device’s 96 electrodes were strategically placed in order to allow the electrical activation of the patient’s “retinotopic map”, which consists of neurons that are spatially arranged to correspond with points in the visual field.
Stimulating these neurons produced basic shapes known as phosphenes, which are made up of white points or lines of light. Sometimes referred to as “floaters”, these strange apparitions are often experienced after we rub our eyes or look at a bright light source. According to the study authors, it took the patient two months of daily training before she was able to discriminate between spontaneous phosphenes and those generated by the implant.
Over time, however, she became more proficient at identifying the shapes produced by the device, and was eventually able to make out distinct shapes. For instance, by stimulating specific neurons within her retinotopic map, the researchers were able to create phosphenes that looked like letters.
Eventually, the patient was able to detect the letters I, L, C, V, and O with 70 percent accuracy. However, the study authors say that “[a]lthough several combinations of electrodes evoked perceptions that resembled letters (such as an inverted ‘U’ or a rotated ‘T’), we were unable to induce the perception of all the letters of the alphabet.”
The researchers also designed a game in which the patient had to determine whether an animation showed Maggie Simpson shooting to the left or the right, while the electrode stimulated the appropriate neurons in order to reveal the direction of movement.
Toward the end of the six-month experiment, the study authors equipped the patient with a head-mounted camera that converted visual inputs into signals that were sent to the electrodes, thus allowing her to “head scan” the objects in front of her. Using this device, she was able to make out a series of black and white bars printed on a strip of cardboard and could identify a white square that appeared in random locations on a black screen.
In a statement, study author Eduardo Fernández explained that “these results are very exciting because they demonstrate both safety and efficacy and could help to achieve a long-held dream of many scientists, which is the transfer information from the outside world directly to the visual cortex of blind individuals, thereby restoring a rudimentary form of sight.”
In spite of this, however, he insists that there is still a lot of work to do before this technology can be used to help restore vision in blind people. “[W]e should be aware that there are still a number of important unanswered questions and that many problems have to be solved before a cortical visual prosthesis can be considered a viable clinical therapy,” he said.