Effect of Stimulus Waveform of Biphasic Current Pulse on Retinal Ganglion Cell Responses in Retinal Degeneration (rd1) mice.
A retinal prosthesis is being developed for the restoration of vision in patients with retinitis pigmentosa (RP) and age-related macular degeneration (AMD). Determining optimal electrical stimulation parameters for the prosthesis is one of the most important elements for the development of a viable retinal prosthesis. Here, we investigated the effects of different charge-balanced biphasic pulses with regard to their effectiveness in evoking retinal ganglion cell (RGC) responses. Retinal degeneration (rd1) mice were used (n=17). From the ex-vivo retinal preparation, retinal patches were placed ganglion cell layer down onto an 8×8 multielectrode array (MEA) and RGC responses were recorded while applying electrical stimuli. For asymmetric pulses, 1st phase of the pulse is the same with symmetric pulse but the amplitude of 2nd phase of the pulse is less than 10 µA and charge balanced condition is satisfied by lengthening the duration of the pulse. For intensities (or duration) modulation, duration (or amplitude) of the pulse was fixed to 500 µs (30 µA), changing the intensities (or duration) from 2 to 60 µA (60 to 1000 µs). RGCs were classified as response-positive when PSTH showed multiple (3~4) peaks within 400 ms post stimulus and the number of spikes was at least 30% more than that for the immediate pre-stimulus 400 ms period. RGC responses were well modulated both with anodic and cathodic phase-1st biphasic pulses. Cathodic phase-1st pulses produced significantly better modulation of RGC activity than anodic phase-1st pulses regardless of symmetry of the pulse.
Department of Physiology, Chungbuk National University School of Medicine, Cheongju 362-763, Korea.
Kun No
KN
Ahn
Department of Physiology, Chungbuk National University School of Medicine, Cheongju 362-763, Korea.
Jeong Yeol
JY
Ahn
Department of Ophthalmology, Chungbuk National University School of Medicine, Cheongju 362-763, Korea.
Jae-Hyung
JH
Kim
Department of Information and Communication Engineering, Chungbuk National University College of Electrical and Computer Engineering, Cheongju 362-763, Korea.
Kyoungrok
K
Cho
Department of Electrical Engineering, University of Ulsan, Ulsan 680-749, Korea.
Kyo-In
KI
Koo
Devision of Neuroscience, Alfaisal University College of Medicine, Riyadh 11533, Kingdom of Saudi Arabia.
Solomon S
SS
Senok
Department of Physiology, Chungbuk National University School of Medicine, Cheongju 362-763, Korea.
Yong Sook
YS
Goo
Anodic phase-1st stimulus; Cathodic phase-1st stimulus; Multi-electrode array (MEA); Retinal ganglion cell (RGC); Retinal prosthesis