Artikel
Evaluation of Neuronal Stimulation Methods for Retinal Bipolar Cells Including New Pulse Density Modulated, Charge Controlled Stimulation Approach
Suche in Medline nach
Autoren
Veröffentlicht: | 7. März 2016 |
---|
Gliederung
Text
Objective: To compare the pulse density modulated, switched capacitor based stimulation (PDM-SCS) approach, developed by Marzouk et al., to the voltage and current controlled stimulation (VCS respectively CCS).
Materials and Methods: Two of the main methods of electrical stimulation for retinal bipolar cells are the VCS and the CCS approach. Because the stimulation current changes with the tissues impedance, the VCS approach offers no control about the injected charge. The CCS method becomes unsafe with decreasing size of the electrodes, because the rising impedance leads to high electrode potentials above the water window, where the electrolytes next to the electrode turn into gas bubbles. To prevent retinal bipolar cells from electric potential exceeding the water window, but still measure the injected charge, the new PDM-SCS approach was introduced, where discrete charges are brought into the retinal cells via switched capacitors. Within an embedded design, the three different stimulation approaches are implemented on a printed circuit board and connected to a retinal tissue emulator. The tissue then got stimulated with all three approaches and the injected charges as well as the stimulation energy were measured.
Results: It is shown that the constructed stimulation module is precise enough to reproduce literature values for CCS and VCS and also fits with the simulation results. Furthermore the results of PDM-SCS were compared to CCS and VCS and show that PDM-SCS has the highest charge injection per stimulation energy.
Discussion: Because of the low output energy, the PDM-SCS approach appears to be an effective stimulation solution to precisely control the injection of high charges without exceeding the water window.
Acknowledgment: This work was supported by the Deutsche Forschungsgemeinschaft (DFG) founding the project (PAK 468).