Andréoletti, Teva

Cessac, Bruno

Chavane, Frederic

Roux, Sébastien

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HAL Id: hal-02167729https://hal.inria.fr/hal-02167729Submitted on 28 Jun 2019HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.L’archive ouverte pluridisciplinaire HAL, estdestinée au dépôt et à la diffusion de documentsscientifiques de niveau recherche, publiés ou non,émanant des établissements d’enseignement et derecherche français ou étrangers, des laboratoirespublics ou privés.Simulating the cortical activity evoked by artificialretinal implantsTeva Andréoletti, Frederic Chavane, Sébastien Roux, Bruno CessacTo cite this version:Teva Andréoletti, Frederic Chavane, Sébastien Roux, Bruno Cessac. Simulating the cortical activityevoked by artificial retinal implants. NeuroMod 2019 - First meeting of the NeuroMod Institute, Jul2019, Fréjus, France. ￿hal-02167729￿Simulating	the	cortical	activity	evoked	by	artificial	retinal	implantsTeva	Andréoletti1,	Frédéric	Chavane2,	Sébastien	Roux2,	Bruno	Cessac11 Inria,	Biovision Team,	Sophia	Antipolis,	Université	Côte	d'Azur,	France,	2 Institut	de	Neurosciences	de	la	Timone,	CNRS,	Aix-Marseille	Université,	Marseille,	France	INTRODUCTIONRecent advances in neuroscience and microelectronics have opened up the possibility of partially restoring vision in blind patients using retinal prostheses. However, it only restoreslow-resolution vision, which may be explained by a poor understanding of how electrical stimulation activates the visual cortex. Our interest focuses on the modeling of retinal andcortical activities in the case of prosthetic stimulation, with the objective of comparing them to the activities evoked by visual stimuli.ACKNOWLEDGEMENTSWe would like to thank our collaborators, Frédéric Chavane and Sébastien Roux from Institut desNeurosciences de la Timone, both for their significant help and their insightful suggestions.REFERENCES[1]			S.	Roux	et	al.,	Probing	the	functional	impact	of	subretinal prosthesis,	eLIFE,	2016[2]			A.	Wohrer,	Model	and	large-scale	simulator	of	a	biological	retina,	with	contrast	gain	control,	PHD	thesis,	University of	Nice-Sophia	Antipolis, 2007[3]			T-K.	Tran,	Large	scale	retinal	modeling	for	the	design	of	new	generation	retinal	prostheses,	PhD	thesis,	University	of	Nottingham,	2015[4]			B.	Durette,	Traitement	du	signal	pour	les	prothèses	visuelles	:	approche	biomimétique	et	sensori-motrice,	PHD	Thesis,	Université	Grenoble	1	- Joseph	Fourier,	2009[5]	C.Gias et	al.,	Retinotopy within	rat	primary	visual	cortex	using	optical	imaging,	NeuroImage,	2005DESCRIPTIVE	DIAGRAMMain	objective:Computational steps:Virtual	Retina[2] •Prosthesis model				•MACULARRetina simulator Comparison of	retinal and	cortical	activitiesVideoImage Pre-processing[4] Prosthesismodel[3,4]Retinalactivitymodel[1]Cortical	activitymodel[1,5]CONCLUSION &	FUTURE PERSPECTIVE• Based on the one-electrode model from Roux et al. [1] , we developed a customizable model providing retinal and corticalactivities for a multi electrode array.• The arrangement of the electrodes needs to be adjusted to better match the design of the most recent prostheses, which willmake it possible to compare simulation results and experimental results with greater accuracy.• The model of information coding by the prosthesis must be added, as well as the preprocessing which has to be applied to theinput image or video. This future work will be inspired from the work done in the theses of T.-K. Tran[3] and B. Durette[4].• Among the perspectives offered by this internship, the study of a dynamic response is of central interest. In this static modelwe do not take into account any of the transient regimes resulting from variations in the signal received by the electrode. Wecan for example focus on the case where an electrode is activated by a pulse or step signal.GENERAL	CONTEXTUsing retinal prostheses has a major disadvantage. The contact betweenthe retina and the matrix of electrode is not perfect. Two diffusion effects aretherefore observed.In particular, Roux et al.[1] have shown, from experiments on rats, that the corticalactivity obtained by optical imaging can be up to ten times higher duringprosthetic stimulation compared to normal visual stimulation.Roux et al.[1] developed a Matlab model in order to study the phenomenon ofexpansion of cortical activity between visual and prosthetic stimulation for oneelectrode. However, retinal prostheses integrate hundreds of electrodes andthere is no study yet about the effect of the simultaneous activation of severalelectrodes reproducing the shape of an object.The goal is now to integrate and develop the model for a single electrode into amulti-electrode model. The Biovision team at Inria is currently designing a retinasimulator, called Macular, aiming at reproducing the retina response tostimulation in normal (stimulation by light) and pathological conditions (electricstimulation by prostheses). Our objective is to compare the results fromprosthetic simulation to normal vision.Figure	ASchematic view of the experimental setup with the camera and the visual pathway from theretina to V1 activated with normal visual stimuli (left) or with sub-retinal electrical stimulationusing a MEA (right).Source: Roux et al.[1]Figure	BCortical activations generated in 2 animals by a single electrode (blue) and a whole multi-electrode array (red) stimulation (top maps) at a high current intensity (± 200 and 150 mArespectively) and their corresponding 20° visual stimulus (white, bottom maps).Source: Roux et al.[1]THE ONE-ELECTRODE	MODELThe model developed by Roux et al.[1] provides retinal and cortical activities for one electrode by taking into account twodiffusions: the direct diffusion around the electrode and the diffusion due to the activation of axons so-called “en passant”(axons of distant retinal ganglion cells).RESULTSFigure	FResult for one electrode. The intersection of the lines represents the position of theblind spot.Figure	GResult obtained by simulating a 6x6 multi-electrodes network. For better visualization,the electrodes were spaced more apart than on a real prosthesis. In this case, theactivations are superimposed due to the diffusion of current between the electrodesand the retina.Figure	CResult for	one	electrode.Figure	DRat retinotopy based on thework of Gias et al.[5]Figure	ECortical activity depending on the size of the electrode and the ratio ofcontribution of axons en passant (in line, 0.5 and 1.0 respectively).Figure	HResults obtained by simulating a 10x10 multi-electrodes network. The test forms weresimulated using intensity levels between 0 and 1.

Simulating the cortical activity evoked by artificial retinal implants

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