bioRxiv ScienceSearch

Biology subjects

Sabatier, Q.

Publications and source records attributed to Sabatier, Q..

2 recordsLinked to original sources

High Temporal Sub-millisecond Time Resolution Stimulation Increases Performances of Retina Prosthetic Vision

Vision loss has an enormous impact on affected individuals, and increasing social and economics costs for the whole of society. Important approaches have been introduced, aimed at restoring visual functionality in the case of vision degradation and loss. Currently the most promising technology is represented by retinal implants, with companies producing devices approved for commercialization. The first clinical studies encouragingly reported perception elicited by both devices. Some patients retrieve autonomy, but only a few could reach satisfactory perception levels, allowing more complex tasks such as reading. Fundamental limitations however still exist in both spatial and temporal resolution, and these limitations call for improvements of the technology and of the stimulation strategies used therein. This study focuses on the importance of temporal resolution for retinal stimulation, and how it can be used to improve restored perception for implanted patients. We show a quantification of the improvement of discrimination performance when stimulating with high frame rates compared to conventional 30-60Hz frame rates. Such effect is evaluated using data collected from implanted patients, and deriving from it a realistic phosphene model. This study allowed to accurately replicate the perceptual effects of the studied technologies, and to evaluate the hypotheses regarding performance improvements using higher temporal resolutions for stimulation strategies in visual restoration devices.

neuroscience

Modeling the Electro-chemical Properties of Microbial Opsin ChrimsonR for Application to Optogenetics-based Vision Restoration

Optogenetic activation of neurons [1] have greatly contributed to our understanding of how neural circuits operate, and holds huge promise in the field of neural prosthetics, particularly in sensory restoration. The discovery of new channelrhodopsins, Chrimson -- which is 45 nm more red-shifted than any previously discovered or engineered channelrhodopsin -- and its mutant ChrimsonR with faster kinetics [2] made this technology available for medical applications. However, a detailed model that would be able to accurately reproduce the membrane potential dynamics in cells transfected with ChrimsonR under light stimulation is missing. We address this issue by developing the first model for the electrochemical behavior of ChrimsonR that predicts its conductance in response to arbitrary light stimulation. Our model captures ON and OFF dynamics of the protein for stimuli with frequencies up to 100 Hz and their relationship with the brightness, as well as its activation curve, the steady-state amplitude of the response as a function of light intensity. Additionally, we capture a slow adaptation mechanism at a timescale at the order of minutes. Our model holds for light intensities covering the whole dynamic range of the channel (from response onset to saturation) and for timescales in the order of up to several minutes. This model is a new step towards modeling the spiking activity of ChrimsonR-expressing neurons, required for the precise control of information transmission in optogenetics-based Brain-Computer Interfaces, and will inform future applications of ChrimsonR based optogenetics.

neuroscience