Adam Cooman – Apics
Modifying a biologically inspired retina simulator to reconstruct realistic responses to moving stimuli
Selma Souihel – Biovision
Virtual Retina is a retina emulator based on a detailed model, that transforms a stimulus into a set of spike trains, as those emitted by retinal ganglion cells. The model includes three stages of processing : the photoreceptors, the bipolar cells and the ganglion cells. The gain control mechanism implemented in the bipolar layer has been adapted in order to reproduce motion anticipation results from Berry & al. (1999). Then a second gain control mechanism has been implemented in the ganglion layer to account for two other features of motion processing : alert response and motion onset. In this case, a simple pooling of bipolar cells by ganglion cells (short-range connectivity) is enough to reconstruct the expected responses. Responses to more complex stimuli (eg. random motion), however, require to add long-range connectivity.
[gview file=”https://phd-seminars-sam.inria.fr/files/2017/03/SouihelSelma.pdf” save=”1″]
Understanding the mechanisms of retinal waves: modeling and experiments
Dora Karvouniari – Biovision
Retinal waves are spontaneous bursts of activity propagating in the developing retina, found to play a central role in shaping the visual system and retinal circuitry. They occur at early stages of development and gradually disappear upon maturation, just before vision is functional. Waves during their second stage (II), are mediated by the combination of autonomous bursting of starburst amacrine cells and their mutual coupling through the neurotransmitter acetylcholine. We propose a biophysical model of the spontaneous bursting coupled starburst amacrine cells during development, suitable for a mathematical analysis using non-linear dynamical systems tools. Based on our model, we predict that the spatiotemporal features of these waves change depending on one physiological parameter, the coupling strength between cells. To test this hypothesis, we performed multi-electrode array recordings on perinatal mice, varying pharmacologically the strength of the cholinergic coupling.