EVALUATION OF ELECTRICAL STIMULUS CURRENT APPLIED TO RETINAL CELLS FOR RETINAL PROSTHESIS

We have proposed a novel retinal prosthesis system with three-dimensionally stacked retinal prosthesis chip. We employ the three-dimensional integration technology to realize the high performance retinal prosthesis system. To restore the visual sensation by stimulating the retinal cells, it is essential to determine the optimal stimulus current for designing retinal prosthesis chips. Therefore, we fabricated a stimulus electrode array on a flexible cable for recording of electrically evoked potential (EEP) to optimize the parameters of stimulus current. As a result of animal experiment, the recorded waveform shows a similar behavior to the visually evoked potential (VEP) waveform, indicating possibilities that the electrical stimulation of the retina can restore visual sensation for the blind patients. Furthermore, we developed the Si microprobe for recording of neuronal signals from the animals' brain. By using fabricated Si microprobe, we successfully recorded the neuronal signals from the brain of monkey. This result indicates that Si microprobe array enable us to performed the advanced recording as compared with conventional EEP recording in future.