scholarly journals Virtual reality validation of naturalistic modulation strategies to counteract fading in retinal stimulation

2021 ◽  
Author(s):  
Jacob Thomas Thorn ◽  
Naig Aurelia Ludmilla Chenais ◽  
Sandrine Hinrichs ◽  
Marion Chatelain ◽  
Diego Ghezzi
Keyword(s):  
Virtual Reality ◽  
Ganglion Cells ◽  
Head Rotation ◽  
Head Movements ◽  
Artificial Vision ◽  
Retinal Ganglion ◽  
Pulse Trains ◽  
Retinal Stimulation ◽  
Active Scanning ◽  
Task Significance

Objective: Temporal resolution is a key challenge in artificial vision. Several prosthetic approaches are limited by the perceptual fading of evoked phosphenes upon repeated stimulation from the same electrode. Therefore, implanted patients are forced to perform active scanning, via head movements, to refresh the visual field viewed by the camera. However, active scanning is a draining task, and it is crucial to find compensatory strategies to reduce it. Approach: To address this question, we implemented perceptual fading in simulated prosthetic vision using virtual reality. Then, we quantified the effect of fading on two indicators: the time to complete a reading task and the head rotation during the task. We also tested if stimulation strategies previously proposed to increase the persistence of responses in retinal ganglion cells to electrical stimulation could improve these indicators. Main results: This study shows that stimulation strategies based on interrupted pulse trains and randomisation of the pulse duration allows significant reduction of both the time to complete the task and the head rotation during the task. Significance: The stimulation strategy used in retinal implants is crucial to counteract perceptual fading and to reduce active head scanning during prosthetic vision. In turn, less active scanning might improve the patient's comfort in artificial vision.

scholarly journals Naturalistic spatiotemporal stimulus modulation during epiretinal stimulation increases the persistence of retinal ganglion cell responsivity

2020 ◽  
Author(s):  
Naïg Aurélia Ludmilla Chenais ◽  
Marta Jole Ildelfonsa Airaghi Leccardi ◽  
Diego Ghezzi
Keyword(s):  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Artificial Vision ◽  
Retinal Ganglion ◽  
Electric Pulses ◽  
Retinal Stimulation ◽  
Electrophysiological Recordings ◽  
Stimulus Modulation ◽  
Stimulation Of ◽  
Blind Patients

AbstractObjectiveRetinal stimulation in blind patients evokes the sensation of discrete points of light called phosphenes, which allows them performing visual guided tasks, such as orientation, navigation, object recognition, object manipulation and reading. However, the clinical benefit of artificial vision in profoundly blind patients is still tenuous, as several engineering and biophysical obstacles keep it away from natural perception. The relative preservation of the inner retinal neurons in hereditary degenerative retinal diseases, such as retinitis pigmentosa, supports artificial vision through the network-mediated stimulation of retinal ganglion cells. However, the response of retinal ganglion cells to repeated electrical stimulation rapidly declines, primarily because of the intrinsic desensitisation of their excitatory network. In patients, upon repetitive stimulation, phosphenes fade out in less than half of a second, which drastically limits the understanding of the percept.ApproachA more naturalistic stimulation strategy, based on spatiotemporal modulation of electric pulses, could overcome the desensitisation of retinal ganglion cells. To investigate this hypothesis, we performed network-mediated epiretinal stimulations paired to electrophysiological recordings in retinas explanted from both male and female retinal degeneration 10 mice.Main resultsThe results showed that the spatial and temporal modulation of the network-mediated epiretinal stimulation prolonged the responsivity of retinal ganglion cells from 400 ms up to 4.2 s.SignificanceA time-varied, non-stationary and interrupted stimulation of the retinal network, mimicking involuntary microsaccades, might reduce the fading of the visual percept and improve the clinical efficacy of retinal implants.

scholarly journals Photovoltaic retinal prosthesis restores high-resolution responses to single-pixel stimulation in blind retinas

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Naïg Aurelia Ludmilla Chenais ◽  
Marta Jole Ildelfonsa Airaghi Leccardi ◽  
Diego Ghezzi
Keyword(s):  
High Resolution ◽  
Ganglion Cells ◽  
Artificial Vision ◽  
Wide Field ◽  
Retinal Ganglion ◽  
Retinal Neurons ◽  
Retinal Prostheses ◽  
Retinal Stimulation ◽  
Single Pixel ◽  
Pixel Pitch

AbstractRetinal prostheses hold the promise of restoring vision in totally blind people. However, a decade of clinical trials highlighted quantitative limitations hampering the possibility of reaching this goal. A key challenge in retinal stimulation is to independently activate retinal neurons over a large portion of the subject’s visual field. Reaching such a goal would significantly improve the perception accuracy in retinal implants’ users, along with their spatial cognition, attention, ambient mapping and interaction with the environment. Here we show a wide-field, high-density and high-resolution photovoltaic epiretinal prosthesis for artificial vision (POLYRETINA). The prosthesis embeds 10,498 physically and functionally independent photovoltaic pixels, allowing for wide retinal coverage and high-resolution stimulation. Single-pixel illumination reproducibly induced network-mediated responses from retinal ganglion cells at safe irradiance levels. Furthermore, POLYRETINA allowed response discrimination with a high spatial resolution equivalent to the pixel pitch (120 µm) thanks to the network-mediated stimulation mechanism. This approach could allow mid-peripheral artificial vision in patients with retinitis pigmentosa.

scholarly journals Response variability to high rates of electric stimulation in retinal ganglion cells

2011 ◽  
Vol 106 (1) ◽  
pp. 153-162 ◽  
Author(s):  
Changsi Cai ◽  
Qiushi Ren ◽  
Neal J. Desai ◽  
Joseph F. Rizzo ◽  
Shelley I. Fried
Keyword(s):  
Retinal Ganglion Cells ◽  
Action Potentials ◽  
Electric Stimulation ◽  
Ganglion Cells ◽  
High Rate ◽  
Retinal Ganglion ◽  
Pulse Trains ◽  
Retinal Stimulation ◽  
Biphasic Waveform ◽  
Different Types

To improve the quality of prosthetic vision, it is important to understand how retinal neurons respond to electric stimulation. Previous studies present conflicting reports as to the maximum rate at which retinal ganglion cells can “follow” pulse trains, i.e., generate one spike for each pulse of the train. In the present study, we measured the response of 5 different types of rabbit retinal ganglion cells to pulse trains of 100–700 Hz. Surprisingly, we found significant heterogeneity in the ability of different types to follow pulse trains. For example, brisk transient (BT) ganglion cells could reliably follow pulse rates up to 600 pulses per second (PPS). In contrast, other types could not even follow rates of 200 PPS. There was additional heterogeneity in the response patterns across those types that could not follow high-rate trains. For example, some types generated action potentials in response to approximately every other pulse, whereas other types generated one spike per pulse for a few consecutive pulses and then did not generate any spikes in response to the next few pulses. Interestingly, in the types that could not follow high-rate trains, we found a second type of response: many pulses of the train elicited a biphasic waveform with an amplitude much smaller than that of standard action potentials. This small waveform was often observed following every pulse for which a standard spike was not elicited. A possible origin of the small waveform and its implication for effective retinal stimulation are discussed.

scholarly journals Single-pixel epiretinal stimulation with a wide-field and high-density retinal prosthesis for artificial vision

2020 ◽  
Author(s):  
Naïg Aurelia Ludmilla Chenais ◽  
Marta Jole Ildelfonsa Airaghi Leccardi ◽  
Diego Ghezzi
Keyword(s):  
High Resolution ◽  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Dendritic Tree ◽  
High Density ◽  
Artificial Vision ◽  
Wide Field ◽  
Retinal Ganglion ◽  
Retinal Stimulation ◽  
Single Pixel

AbstractRetinal prostheses hold the promise of restoring artificial vision in profoundly and totally blind people. However, a decade of clinical trials highlighted quantitative limitations hampering the possibility to reach this goal. A key obstacle to suitable retinal stimulation is the ability to independently activate retinal neurons over a large portion of the subject’s visual field. Reaching such a goal would significantly improve the perception accuracy in the users of retinal implants, along with their spatial cognition, attention, ambient mapping and interaction with the environment. Here we show a wide-field, high-density and high-resolution photovoltaic epiretinal prosthesis for artificial vision. The prosthesis embeds 10,498 physically and functionally independent photovoltaic pixels allowing for both wide retinal coverage and high-resolution stimulation. Single-pixel illumination reproducibly induced network-mediated responses from retinal ganglion cells at safe irradiance levels. Furthermore, the prosthesis enables a sub-receptive field response resolution for retinal ganglion cells having a dendritic tree larger than the pixel’s pitch. This approach could allow the restoration of mid-peripheric artificial vision in patients with retinitis pigmentosa.

scholarly journals The effects of remote retinal stimulation on the responses of cat retinal ganglion cells.

1977 ◽  
Vol 269 (1) ◽  
pp. 177-194 ◽  
Author(s):  
H B Barlow ◽  
A M Derrington ◽  
L R Harris ◽  
P Lennie
Keyword(s):  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Retinal Ganglion ◽  
Retinal Stimulation

scholarly journals Epiretinal stimulation with local returns enhances selectivity at cellular resolution

2018 ◽  
Author(s):  
Victoria H. Fan ◽  
Lauren E. Grosberg ◽  
Sasidhar S. Madugula ◽  
Pawel Hottowy ◽  
Wladyslaw Dabrowski ◽  
...  
Keyword(s):  
Ganglion Cells ◽  
Electrode Array ◽  
Artificial Vision ◽  
Retinal Ganglion ◽  
Retinal Neurons ◽  
Cellular Resolution ◽  
Electrode Recording ◽  
Current Spread ◽  
Evoked Activity

AbstractObjectiveEpiretinal prostheses are designed to restore vision in people blinded by photoreceptor degenerative diseases, by directly activating retinal ganglion cells (RGCs) using an electrode array implanted on the retina. In present-day clinical devices, current spread from the stimulating electrode to a distant return electrode often results in the activation of many cells, potentially limiting the quality of artificial vision. In the laboratory, epiretinal activation of RGCs with cellular resolution has been demonstrated with small electrodes, but distant returns may still cause undesirable current spread. Here, the ability of local return stimulation to improve the selective activation of RGCs at cellular resolution was evaluated.ApproachA custom multi-electrode array (512 electrodes, 10 μm diameter, 60 μm pitch) was used to simultaneously stimulate and record from RGCs in isolated primate retina. Stimulation near the RGC soma with a single electrode and a distant return was compared to stimulation in which the return was provided by six neighboring electrodes.Main resultsLocal return stimulation enhanced the capability to activate cells near the central electrode (<30 μm) while avoiding cells farther away (>30 μm). This resulted in an improved ability to selectively activate ON and OFF cells, including cells encoding immediately adjacent regions in the visual field.SignificanceThese results suggest that a device that restricts the electric field through local returns could optimize activation of neurons at cellular resolution, improving the quality of artificial vision.Novelty & SignificanceThe effectiveness of local return stimulation for enhancing the electrical activation of retinal neurons was tested using high-density multi-electrode recording and stimulation in isolated macaque retina. The results suggest that local returns may reduce unwanted evoked activity and thus optimize the selectivity of stimulation at cellular resolution. Similar patterns could be implemented in a future high-resolution prosthesis to permit a more faithful replication of normal retinal activity for the treatment of incurable blindness.

Neural activity of functionally different retinal ganglion cells can be robustly modulated by high-rate electrical pulse trains

2020 ◽  
Vol 17 (4) ◽  
pp. 045013 ◽  
Author(s):  
Madhuvanthi Muralidharan ◽  
Tianruo Guo ◽  
Mohit N Shivdasani ◽  
David Tsai ◽  
Shelley Fried ◽  
...  
Keyword(s):  
Retinal Ganglion Cells ◽  
Neural Activity ◽  
Ganglion Cells ◽  
Electrical Pulse ◽  
High Rate ◽  
Retinal Ganglion ◽  
Pulse Trains

scholarly journals Comparison of optomotor and optokinetic reflexes in mice

2017 ◽  
Vol 118 (1) ◽  
pp. 300-316 ◽  
Author(s):  
Friedrich Kretschmer ◽  
Momina Tariq ◽  
Walid Chatila ◽  
Beverly Wu ◽  
Tudor Constantin Badea
Keyword(s):  
Eye Movements ◽  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Head Movements ◽  
Retinal Ganglion ◽  
Optomotor Response ◽  
Optokinetic Response ◽  
Stimulus Velocity ◽  
Image Stabilization ◽  
Optokinetic Responses

During animal locomotion or position adjustments, the visual system uses image stabilization reflexes to compensate for global shifts in the visual scene. These reflexes elicit compensatory head movements (optomotor response, OMR) in unrestrained animals or compensatory eye movements (optokinetic response, OKR) in head-fixed or unrestrained animals exposed to globally rotating striped patterns. In mice, OMR are relatively easy to observe and find broad use in the rapid evaluation of visual function. OKR determinations are more involved experimentally but yield more stereotypical, easily quantifiable results. The relative contributions of head and eye movements to image stabilization in mice have not been investigated. We are using newly developed software and apparatus to accurately quantitate mouse head movements during OMR, quantitate eye movements during OKR, and determine eye movements in freely behaving mice. We provide the first direct comparison of OMR and OKR gains (head or eye velocity/stimulus velocity) and find that the two reflexes have comparable dependencies on stimulus luminance, contrast, spatial frequency, and velocity. OMR and OKR are similarly affected in genetically modified mice with defects in retinal ganglion cells (RGC) compared with wild-type, suggesting they are driven by the same sensory input (RGC type). OKR eye movements have much higher gains than the OMR head movements, but neither can fully compensate global visual shifts. However, combined eye and head movements can be detected in unrestrained mice performing OMR, suggesting they can cooperate to achieve image stabilization, as previously described for other species. NEW & NOTEWORTHY We provide the first quantitation of head gain during optomotor response in mice and show that optomotor and optokinetic responses have similar psychometric curves. Head gains are far smaller than eye gains. Unrestrained mice combine head and eye movements to respond to visual stimuli, and both monocular and binocular fields are used during optokinetic responses. Mouse OMR and OKR movements are heterogeneous under optimal and suboptimal stimulation and are affected in mice lacking ON direction-selective retinal ganglion cells.

scholarly journals Differential stimulation of the retina with glutamate toward a neurotransmitter-based retinal prosthesis

2016 ◽  
Author(s):  
Corey M. Rountree ◽  
Samsoon Inayat ◽  
John B. Troy ◽  
Laxman Saggere
Keyword(s):  
Visual Information ◽  
Ganglion Cells ◽  
Retinal Ganglion ◽  
Retinal Prostheses ◽  
Retinal Stimulation ◽  
Stimulation Parameters ◽  
Normal Means ◽  
Retinal Pathways ◽  
Pulsatile Delivery ◽  
Stimulation Of

ABSTRACTSubretinal stimulation of the retina with neurotransmitters, the normal means of conveying visual information, is a potentially better alternative to electrical stimulation widely used in current retinal prostheses for treating blindness from photoreceptor degenerative diseases. Yet, no retinal stimulation study exploiting the inner retinal pathways exists. Here, we demonstrate the feasibility of differentially stimulating retinal ganglion cells (RGCs) through the inner nuclear layer of the retina with glutamate, a primary neurotransmitter chemical, in a biomimetic way. We show that controlled pulsatile delivery of glutamate into the subsurface of explanted wild-type rat retinas elicits highly localized simultaneous inhibitory and excitatory spike rate responses in OFF and ON RGCs. We also present the spatiotemporal characteristics of RGC responses to subretinally injected glutamate and the therapeutic stimulation parameters. Our findings could pave the way for future development of a neurotransmitter-based subretinal prosthesis offering more naturalistic vision and better visual acuity than electrical prostheses.

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