Temporal response properties of retinal ganglion cells in rd1 mice evoked by amplitude-modulated electrical pulse trains.
OBJECTIVE
The electrophysiological properties of degenerated retinas responding to amplitude-modulated electrical pulse trains were investigated to provide a guideline for the development of a stimulation strategy for retinal prostheses.


METHODS
The activities of retinal ganglion cells (RGCs) in response to amplitude-modulated pulse trains were recorded from an in vitro model of retinal prosthesis, which consisted of an rd1 mouse retinal patch attached to a planar multielectrode array. The ability of the population activities of RGCs to effectively represent, or encode, the information on the visual intensity time series, when the intensity of visual input is transformed to pulse amplitudes, was investigated.


RESULTS
An optimal pulse amplitude range was selected so that RGC firing rates increased monotonically and linearly. An approximately 10-Hz rhythm was observed in the field potentials from degenerated retinas, which resulted in a rhythmic burst of spontaneous spikes. Multiple peaks were present in poststimulus time histograms, with interpeak intervals corresponding to the oscillation frequency of the field potentials. Phase resetting of the field potential oscillation by stimulation was consistently observed. Despite a prominent alteration of the properties of electrically evoked firing with respect to normal retinas, RGC response strengths could be modulated by pulse amplitude. Accordingly, the temporal information of stimulation could be faithfully represented in the RGC firing patterns by an amplitude-modulated pulse train.


CONCLUSIONS
The results suggest that pulse amplitude modulation is a feasible means of implementing a stimulation strategy for retinal prostheses, despite the marked change in the physiological properties of RGCs in degenerated retinas.
Ryu
Sang Baek
SB
Department of Biomedical Engineering, College of Health Science, Yonsei University, Wonju, Kangwon-do, South Korea.
Ye
Jang Hee
JH
Goo
Yong Sook
YS
Kim
Chi Hyun
CH
Kim
Kyung Hwan
KH
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D004195:Disease Models, Animal; D004558:Electric Stimulation / Q000379:methods*; D004567:Electrodes, Implanted; D005074:Evoked Potentials, Visual / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D012162:Retinal Degeneration / Q000503:physiopathology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D012684:Sensory Thresholds