Spatiotemporal characteristics of retinal response to network-mediated photovoltaic stimulation
Abstract
Subretinal prostheses aim at restoring sight to patients blinded by photoreceptor degeneration using electrical activation of the surviving inner retinal neurons. Today, such implants deliver visual information with low-frequency stimulation, resulting in discontinuous visual percepts. We measured retinal responses to complex visual stimuli delivered at video rate via a photovoltaic subretinal implant and by visible light. Using a multielectrode array to record from retinal ganglion cells (RGCs) in the healthy and degenerated rat retina ex vivo, we estimated their spatiotemporal properties from the spike-triggered average responses to photovoltaic binary white noise stimulus with 70-μm pixel size at 20-Hz frame rate. The average photovoltaic receptive field size was 194 ± 3 μm (mean ± SE), similar to that of visual responses (221 ± 4 μm), but response latency was significantly shorter with photovoltaic stimulation. Both visual and photovoltaic receptive fields had an opposing center-surround structure. In the healthy retina, ON RGCs had photovoltaic OFF responses, and vice versa. This reversal is consistent with depolarization of photoreceptors by electrical pulses, as opposed to their hyperpolarization under increasing light, although alternative mechanisms cannot be excluded. In degenerate retina, both ON and OFF photovoltaic responses were observed, but in the absence of visual responses, it is not clear what functional RGC types they correspond to. Degenerate retina maintained the antagonistic center-surround organization of receptive fields. These fast and spatially localized network-mediated ON and OFF responses to subretinal stimulation via photovoltaic pixels with local return electrodes raise confidence in the possibility of providing more functional prosthetic vision.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 01, 2018
- Source ID
- 10.1152/jn.00872.2016
Entities
People
- Alexander Sher
- Daniel Palanker
- Elton Ho
- Georges Goetz
- James Harris
- Keith Mathieson
- Ludwig Galambos
- Richard D. Smith
- Theodore I Kamins
- Xin Lei
Organizations
- National Institutes of Health
- Stanford University
- The Pew Charitable Trusts
- United States Department of Defense
- University of California
- University of Strathclyde