Scientists from Ecole Polytechnique Fédérale (EPFL) de Lausanne are investigating new ways to provide visual signals to the blind by directly stimulating the optic nerve. Their preliminary study uses a new type of neural electrode and provides distinct signals. The technology bypasses the eyeball entirely and sends messages to the brain. This is achieved by stimulating the optic nerve with a new type of intraneural electrode.
Previous attempts to stimulate the optic nerve in the 1990s provided inconclusive results. “Back then, they used cuff nerve electrodes,” says EPFL's Medtronic Chair in Neuroengineering Diego Ghezzi. “The problem is that these electrodes are rigid and they move around, so the electrical stimulation of the nerve fibers becomes unstable. The patients had a difficult time interpreting the stimulation, because they kept on seeing something different.”
Together, Ghezzi, Micera and their teams engineered an electrode array of 12 electrodes. In order to understand how effective these are at stimulating the various nerve fibres within the optic nerve, scientists delivered electric current to the optic nerve and measured the brain's activity in the visual cortex. They developed an elaborate algorithm to decode the cortical signals and showed that each stimulating electrode induces a specific and unique pattern of cortical activation. This suggests that intraneural stimulation of the optic nerve is selective and informative.
These findings are exciting but more research is needed to learn about the visual perception behind the cortical patterns. “For now, we know that intraneural stimulation has the potential to provide informative visual patterns,” says Ghezzi. “For now, we know that intraneural stimulation has the potential to provide informative visual patterns. It will take feedback from patients in future clinical trials in order to fine-tune those patterns.”