Probing the functional impact of sub-retinal prosthesis.

Sébastien Roux,Florent Dupont,Sylvain Takerkart,Pascale Pham,Louis Hoffart,Frédéric Chavane,Serge Picaud,Frédéric Matonti

doi:10.7554/elife.12687

Abstract

Retinal prostheses are promising tools for recovering visual functions in blind patients but, unfortunately, with still poor gains in visual acuity. Improving their resolution is thus a key challenge that warrants understanding its origin through appropriate animal models. Here, we provide a systematic comparison between visual and prosthetic activations of the rat primary visual cortex (V1). We established a precise V1 mapping as a functional benchmark to demonstrate that sub-retinal implants activate V1 at the appropriate position, scalable to a wide range of visual luminance, but with an aspect-ratio and an extent much larger than expected. Such distorted activation profile can be accounted for by the existence of two sources of diffusion, passive diffusion and activation of ganglion cells' axons en passant. Reverse-engineered electrical pulses based on impedance spectroscopy is the only solution we tested that decreases the extent and aspect-ratio, providing a promising solution for clinical applications.

Highlights

Blindness affects 45 million people around the world with an increase of 1 to 2 million people each year (Resnikoff et al, 2004)
Note that our model suggests that the isotropy observed for whole Micro Electrode Arrays (MEAs) (wMEA) activations results from the geometrical arrangement between the electrode size and the shadow cone
Further investigations will have to probe the dynamical aspect of these prosthetic activation to better understand how to generate spatio-temporal activations in the visual pathway (Elfar et al, 2009; Fried et al, 2006) that are similar to the ones observed in response to natural stimuli

Summary

Introduction

Blindness affects 45 million people around the world with an increase of 1 to 2 million people each year (Resnikoff et al, 2004). The genetic alterations and the mechanisms subtending photoreceptor death are well described, and therapeutic strategies are under clinical trials (Ferrari et al, 2013; Talcott et al, 2011), retinal degeneration inexorably leads to blindness (Tsujikawa et al, 2008). In this perspective, retinal prostheses provide a promising solution that remains to date a unique alternative for the patients. Improving the performances of such implants is a key strategic issue for further developments

Methods

Results

Discussion

Conclusion