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Sang Baek Ryu, Jang Hee Ye, Yong Sook Goo, Kyung Hwan Kim; Encoding of Natural Scene in RGC Spike Trains of Photoreceptor-Degenerated Retina by Multichannel Electrical Stimulation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4960.
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© ARVO (1962-2015); The Authors (2016-present)
For successful restoration of visual function by retinal implant, electrically-evoked neural activities should represent spatiotemporal information of incoming visual scene. The purpose of this study is to investigate whether it is possible to encode multichannel temporal information of natural scene in retinal ganglion cell (RGC) spike trains by stimulation of multichannel electrical pulse trains.
Retinas of rd1 mice were attached to a 64-channel planar microelectrode array (MEA). Spontaneous and stimulated single-unit RGC activities were recorded. Biphasic pulse trains for stimulation were obtained by modulating their amplitudes according to light intensity variation of natural scenes. Two independent stimulation pulse trains were simultaneously applied to two stimulation electrodes. Spike train decoding was applied to multiple RGC spike trains to reconstruct the pulse amplitude time-series. The decoding accuracy was utilized to quantify the effectiveness of prosthetic stimulation.
Abnormal oscillatory background rhythms (~10 Hz) were consistently present in evoked rd1 spike activities as well as in spontaneous spikes and field potentials. The RGCs responded not only to distant stimuli as well as nearby pulse trains, presumably due to the current spread. However, when the amplitude modulation range was determined elaborately, the two time-series corresponding to the amplitudes of pulse trains simultaneously applied could be successfully reconstructed from RGC spike trains.
The results extend previous findings on the possibility of visual information encoding by electrical stimulation in normal retinas, to the degenerated retina in which the neural activities are significantly altered, and thus support the feasibility of temporal information encoding by retinal prosthesis.
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