Purchase this article with an account.
KUN NO AHN, Yeong Jun Song, Yongsook Goo; Polarity Effects on Electrically Stimulated Retinal Ganglion Cell (RGC) Responses in rd1 mice. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5520.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Retinal prosthesis has been developed for the patients with retinitis pigmentosa (RP) and age related macular degeneration (AMD), and is regarded as the most feasible method to restore vision. Extracting optimal electrical stimulation parameters for the prosthesis is one of the most important elements for the success of retinal prosthesis. Here, we used charge balanced biphasic current pulse and we tested polarity sensitivity of evoking RGC responses by using anodic phase-1st and cathodic phase-1st biphasic pulse.
The well-known animal model for RP, rd1 (Pde6brd1) mice at postnatal 8 weeks were used. From the ex-vivo retinal preparation, retinal waveforms were recorded with 8 x 8 MEA. Biphasic current pulses in the form of anodic phase-1st and cathodic phase-1st were applied once per second (x50). For intensity modulation, duration of the pulse was fixed to 500 us and the intensities of the pulse were modulated from 2 to 60 uA. For duration modulation, intensity of the pulse was fixed to 30 uA and the durations of the pulse were modulated from 60 us to 1000 us. The electrically-evoked RGC spikes was defined as positive when the number of RGC spikes for 400 ms after stimulus was 1.3 times higher than that for 400 ms before stimulus in post-stimulus time histogram.
RGC responses were well modulated both with anodic phase-1st and cathodic phase-1st biphasic pulse by varying the intensity and duration of the pulse. Our results show that RGC response is preferentially activated by cathodic phase-1st pulse, regardless of modulation type (intensity or duration). Therefore, the threshold charge density is always lower with cathodic phase-1st pulse than anodic phase-1st pulse (duration modulation; 419.1 μC/cm2 vs. 459.87 μC/cm2, amplitude modulation; 380.54 μC/cm2 vs. 481.25 μC/cm2).
Cathodic phase-1st pulse is always efficient than anodic phase-1st pulse both in amplitude modulation and duration modulation.
This PDF is available to Subscribers Only