Welcome to the first MxW Monthly Must-Reads (MMM) of 2019! This month’s selection of articles focuses on retina research. The retina, an extension of the brain and the first stage of visual input processing, extracts information about various features of visual stimuli, including size, contrast, colour, orientation and motion direction. With a diversity of neural subtypes both on the levels of local processing and downstream output via retinal ganglion cells, the retina is an amazing model for studying functional sub-circuits in terms of morphology, connectivity, and firing dynamics. A range of physiological, molecular, genetic and computational approaches can be used to reveal the structure and function of retinal circuits. This month’s MMM covers five articles that explore various aspects of retinal organisation and computation using these approaches. The complexity revealed highlights the importance of high-density microelectrode array technology in supporting in vitro retinal investigations.

  1. How diverse retinal functions arise from feedback at the first visual synapse
    by Antonia Drinnenberg, Felix Franke, Rei K. Morikawa, Josephine Jüttner, Daniel Hillier, Peter Hantz, Andreas Hierlemann, Rava Azeredo da Silveira and Botond Roska. Neuron. July 2018.

    The authors investigated how a specific type of interneuron, the horizontal cell, contributes to input-output transformations of the mouse retina. By perturbing horizontal cell function while recording light-induced spiking activity from thousands of retinal ganglion cells using high-density microelectrode arrays (MaxOne Technology), the researchers uncovered six distinct effects on retinal ganglion cell response range and dynamics. The responses could be sharpened, scaled, or delayed, depending on the retinal ganglion cell type. This work demonstrates that a single type interneuron can differentially modulate several distinct output channels of the retina.

    Read the paper here. More information can be found here and here.

  2. Correlations between specific patterns of spontaneous activity and stimulation efficiency in degenerated retina 
    by Christine Haselier, Sonia Biswas, Sarah Rösch, Gabriele Thumann, Frank Müller and Peter Walter. PLoS ONE. December 2017.

    How efficient are retinal prostheses in stimulating degenerated retinae, which exhibit abnormal activity patterns? Using mouse models of retinal degeneration, the researchers recorded electrical activity patterns of retinal ganglion cells in whole-mounted retinae with a microelectrodearray(MEA) system. Abnormal oscillations and burst firing was found, correlating with a reduced excitability of the retinalganglion cells. Further using the MEA to deliver electrical stimulation, the authors could modify the pathological retinal activity until it resembled wild type patterns, which sometimes enhanced stimulation efficiency. This work could be inspiring for developing more efficient retinal prostheses in the future.

    Read the paper here.

  3. Large scale matching of function to the genetic identity of retinal ganglion cells 
    by Filippo Pisano, Erin Zampaglione, Niall McAlinden, Jennifer Roebber, Martin D. Dawson, Keith Mathieson and Alexander Sher. Scientific Reports. November 2017.

    This study presents a novel technique that brings together large-scale microelectrode arraytechnology, optogenetics and confocal imaging to characterise the activity of sub-populations of mouse retinal ganglion cells (RGCs) in the context of their genetic identity and morphology. MEA technology provides one of the best methods for recording retinal responses to visual stimuli for large populations of neurons simultaneously. Meanwhile, optogenetic stimulation and high-speed confocal imaging of genetically-labeled RGCs can reveal soma location and partial cellular morphologies. This method offers a powerful tool for matching function to genetic classification in retinal networks.

    Read the paper here.

  4. Orientation-selective retinal circuits in vertebrates
    by Paride Antinucci and Robert Hindges. Front. Neural Circuits. February 2018.

    The authors review different orientation-selective retinal cell types found in various vertebrate species, including the mouse, rabbit, primate, cat, and zebrafish. They compare similarities and differences in cell morphology, function and firing mechanisms and discuss the most interesting findings that could shape our current understanding of retinal neural computation in the vertebrate visual systems.

    Read the paper here.

  5. Cellular and circuit mechanisms shaping the perceptual properties of the primate fovea
    by Raunak Sinha, Mrinalini Hoon, Jacob Baudin, Haruhisa Okawa, Rachel O.L. Wong and Fred Rieke. Cell. January 2017.

    In this article, the authors want to understand the mechanisms underlying the higher visual chromatic and spatial acuity of the primate fovea compared to the peripheral region of the retina. Intracellular recordings and structure-function analysis revealed that the midget ganglion cells in foveal and peripheral regions of the retina use different inhibition mechanisms to control sensitivity to rapid variation in light inputs. The differences in temporal sensitivity can be explained by the properties of the foveal cone photoreceptors, which exhibited slower light responses than peripheral cones.

    Read the paper here. More about this article can be found here.