gms | German Medical Science

Objective: We have proposed that arrays of intracortical microelectrodes, such as the Utah Electrode Array (UEA), might form the foundation for the restoration of a useful visual sense. The objective of this study is to evaluate the efficacy of intracortical microelectrodes in providing a limited but useful sense of vision to individuals who are profoundly blind.

Methods: We implanted an intracortical 96-channel microelectrode array in the occipital cortex of 4 blind volunteers for 6 months. We collected multielectrode recordings, thresholds, phosphene maps, and descriptive feedback regarding the features of evoked perceptions. We investigated if the volunteers could integrate the electrical stimulation of the visual cortex into meaningful perceptions for daily living activities. After completing the 6-month study period, the implanted electrode arrays and the external connectors were explanted.

Results: The implantation and subsequent explantation of the intracortical microelectrode arrays were performed without complications. We consistently obtained high-quality recordings and the stimulation parameters remained stable over time. Microstimulation evoked simple and complex phosphenes at stable locations in visual space. The evoked perceptions allowed the participants to identify some letters, recognize object boundaries, and were of significant help in performing orientation and mobility tasks. Additionally, our results show that we can accurately predict phosphene thresholds, brightness levels, and the number of perceived phosphenes from the recorded neural signals.

Conclusion: Our results validate and support our previous findings, demonstrating the safety and efficacy of intracortical microstimulation using a large number of electrodes in humans. These results highlight the potential of a cortical visual prosthesis. However, there are still a relevant number of open questions, and more experiments should be done to achieve the clinical goals envisioned by t