When : October 22, 2019 at 10 am
Where : Inria Sophia Antipolis – Méditerranée, room Euler violet
Speaker : Dr. Helene Schreyer (Inria, Biovision project-team)
Title : When 1-1 ≠0 for bipolar cells – Nonlinear spatial integration under artificial and natural stimuli
Abstract : Vision begins in the eye where the visual signal is processed in two synaptic layers before being transmitted by the ganglion cells to the brain. The ganglion cells separate the visual input into ~30 parallel output channels. A pivotal role in shaping these output channels is taken up by retinal bipolar cells, which provide the excitatory inputs to ganglion cells for extracting different visual features. In particular, nonlinearities in bipolar-to-ganglion cell signaling seem to play an important role for different computations performed by ganglion cells. Yet, the exact nature of the nonlinear signals remains obscure and bipolar cell voltage signals are often assumed to be linear. In this talk, I will show that bipolar cells are not simple linear neurons. Based on intracellular recordings in isolated salamander retinas, we found that a sizeable fraction of bipolar cells represent contrast and spatial information in a nonlinear way at their soma. Furthermore, I will show that the linear-nonlinear model (LN model) fails to predict responses of bipolar cells under artificial and natural visual stimuli. The nonlinearities appear to be correlated to temporal properties of bipolar cells but not to the strength of the surround suppression. These data reveal that the nonlinearities in bipolar-to-ganglion cell signaling starts earlier than previously thought, that is, before the axon terminals, at the inputs to bipolar cells.
Bio : Helene Schreyer did her PhD with Tim Gollisch (University of Göttingen, Germany) and is currently a post-doctoral researcher with Tim. She combines single cell recordings from bipolar cells with multielectrode array recordings from ganglion cells. Her work focuses on nonlinear properties of bipolar cells and signal transmission from bipolar to ganglion cells under artificial and natural light stimulation. She studied Neuropsychology and did her master thesis with Pascal Fries and Ayelet Landau ( Ernst Strüngmann Institute for Neuroscience, Frankfurt) on attentional modulation of brain rhythms in the visual cortex.
- April 2014 – May 2018 → PhD in Neuroscience, Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences (GGNB)
- Feb 2011 – October 2013 → M.Sc. in Psychology (focus Neuropsychology) at the University of Bern, CH