Optic nerve and retinal electrostimulation in rats: direct activation of the retinal ganglion cells

Visual prosthesis is competing with biological approaches to restore vision to the blind. Understanding and developing the ability to replicate the neural code of the retina are key factors that can bring bionic vision significant advantage. Here, electrically evoked potentials were recorded in anesthetized rats from the dorsal surface of the superior colliculus. Electrical stimuli of different amplitudes were delivered at the retina and the optic nerve. An evoked potential appeared in both cases within the first 5 ms post-stimulus suggesting that this component of the response was initiated by direct activation of the retinal ganglion cells. However, in the case of retinal neurostimulation, a second evoked potential occurred $9.0 \pm 3.4$ ms after the stimulus delivery. Because this component was not present in the case of optic nerve electrostimulation, it is expected to be originated by the activation of other cells in the retinal network.