Analysis of retinal and cortical response to electrical stimulation by subretinal implant in rodent

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Abstract

Purpose

This aims to develop and improve the use of retinal prosthesis in animal model For that purpose we measured retinal and cortical response to direct subretinal electrical stimulation to understand how the patterns of stimuli can be adapted to improve stimulation to get closer to the response evoked by natural visual stimuli

Methods

In a rat model, a comparative analysis of the functional impact of similar stimulation of a subretinal implant is done at two levels (1)in the retina in vitro by multi electrodes array (2)in vivo in the primary visual cortex by optical imaging recordings Optical imaging permits a functional mapping of the cortex, using light reflection and absorption changes depending on the rate of blood oxygenation Diverse parameters were investigated: stimulus shape and polarity,intensity,size and location

Results

At the cortical level we have quantified the size, position and intensity of the point-spread function in response to the various electrical stimulations and compared them to those generated by calibrated light stimuli. The point-spread function was much larger for electrical stimulations compared to visual stimulation We have performed retinal recordings of ganglion cells, while the prosthesis is on the photoreceptor side The cortical response and the recruitment of ganglion cells respond according to a logarithmic equation The ability to evaluate in vitro within the retina and in vivo the cortical responses induced by the prosthesis allowed us refining the patterns of electrical stimulation to get closer to a natural activation

Conclusion

These results offer interesting prospect for improving the design of prostheses as well as their patterns of stimulation for a medical application

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