Focal Electrical Stimulation of Major Ganglion Cell Types in the Primate Retina for the Design of Visual Prostheses

Abstract

Electrical stimulation of retinal neurons with an advanced retinal prosthesis may eventually provide high-resolution artificial vision to the blind. However, the success of future prostheses depends on the ability to activate the major parallel visual pathways of the human visual system. Electrical stimulation of the five numerically dominant retinal ganglion cell types was investigated by simultaneous stimulation and recording in isolated peripheral primate (Macaca sp.) retina using multi-electrode arrays. ON and OFF midget, ON and OFF parasol, and small bistratified ganglion cells could all be activated directly to fire a single spike with submillisecond latency using brief pulses of current within established safety limits. Thresholds for electrical stimulation were similar in all five cell types. In many cases, a single cell could be specifically activated without activating neighboring cells of the same type or other types. These findings support the feasibility of direct electrical stimulation of the major visual pathways at or near their native spatial and temporal resolution.

A Treatise of the Physical Aspects of Phosphenes and Single-Cell Selectivity in Retinal Stimulation

“…Experimental findings by Jepson [73] indicated similar thresholds for electrical stimulation of the five numerically dominant retinal ganglion cell types previously mentioned. These findings indicate that ON and OFF type cells fire temporally in phase [74].…”

“…Margalit [75] reported similar findings in tiger salamander retina. In many cases, a single cell could be individually stimulated without activating adjacent cells of the same type or other types [73].…”

“…This is because ON and OFF type cells are spatially intermixed [78] and the bright response of ON type cells overshadows the response of OFF cells and their activation is more preferred [74]. While the stimulus is delivered to the cells, the activation area can indicate the stimulation of RGCs regardless of the type and class because they have similar activation thresholds [71][72][73]. ON and OFF type cells are contained within the activation area.…”

Functional architecture of the retina: Development and disease

“…However, strategies that bypass the conventional phototransduction cascade share a common problem in that they lead to a much-diminished light operating range for the stimulated cells. The optimal parameters for stimulating retinal ganglion cells in order to reach their native spatial and temporal resolution is being established in primate (macaque) retina (Jepson et al, 2013). Features such as color vision or a complete representation of the visual field are still distant goals, in part because of the technical limitations, but mostly because our knowledge of how the retina processes visual information is still incomplete.…”

Developments in neural vision technology

“…For faithful replication of the RGC spiking pattern we should stimulate RGCs of each cell type independently, according to how that specific cell type would respond to the input visual stimulus. Work on cell-type selective activation has been carried out with primate retina using single electrode stimulation [23] and two or three neighboring electrodes for stimulation [24]. Third, stimulation of an RGC may also stimulate a nearby axon from a distant cell or a bundle of axons from multiple distant cells.…”