June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Isolating the circuit components behind contrast adaptation within the Rod-Bipolar pathway
Author Affiliations & Notes
  • Gregory Edward Perrin
    Program in Neuroscience and Cognitive Science, University of Maryland, College Park, Maryland, United States
    Biology, University of Maryland, Washington, District of Columbia, United States
  • Joseph Pottackal
    Interdepartmental Program in Neuroscience, Yale University, New Haven, Connecticut, United States
    Department of Ophthalmology & Visual Science, Yale University, New Haven, Connecticut, United States
  • Daniel Butts
    Biology, University of Maryland, Washington, District of Columbia, United States
    Program in Neuroscience and Cognitive Science, University of Maryland, College Park, Maryland, United States
  • Jonathan B Demb
    Department of Ophthalmology & Visual Science, Yale University, New Haven, Connecticut, United States
    Department of Cellular & Molecular Physiology, Yale University, New Haven, Connecticut, United States
  • Joshua H Singer
    Biology, University of Maryland, Washington, District of Columbia, United States
    Program in Neuroscience and Cognitive Science, University of Maryland, College Park, Maryland, United States
  • Footnotes
    Commercial Relationships   Gregory Perrin, None; Joseph Pottackal, None; Daniel Butts, None; Jonathan Demb, None; Joshua Singer, None
  • Footnotes
    Support  US DoE GAANN (G.E.P.), NSF GRF (J.P), NIH R01 EY021372-06 (J.B.D & J.H.S)
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 2978. doi:
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    • Get Citation

      Gregory Edward Perrin, Joseph Pottackal, Daniel Butts, Jonathan B Demb, Joshua H Singer; Isolating the circuit components behind contrast adaptation within the Rod-Bipolar pathway. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2978.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Visual stimuli with significant temporal variability are encoded by a relatively small range of ganglion cell (GC) firing rates. Here, we assess stimulus coding by identified inner retinal circuits presynaptic to GCs by optogenetic and computational methods. We focus on a single computation, the gain control responsible for contrast adaptation.

Methods : Retinas were extracted from two strains of mice with Cre-mediated ChR2 expression in either rod bipolar (RB) cells or CRH-1 amacrine cells (ACs). Voltage-clamp recordings were made from ON alpha GCs, which receive input from RBs and CRH-1 ACs. RBs communicate with ON-alpha GCs as follows: RB->ON cone bipolar (CB)->GC (excitation) and RB->AII->ON cone bipolar (CB)->AC->GC (inhibition); CRH-1 ACs make direct inhibitory synapses onto ON-alpha GCs. With photoreceptor-mediated signaling blocked, temporally modulated white noise stimuli evoked ChR2-driven responses. Linear-Nonlinear (LN) and more complex nonlinear cascade models were used to analyze signal transfer and contrast adaptation.

Results : Excitatory synaptic inputs to ON-alpha GCs show contrast adaptation. This mechanism was sensitive to TPMPA (a GABACR antagonist), suggesting a role for presynaptic inhibition of transmission from bipolar cells. The transformation from stimulus to synaptic current was captured by conventional LN models, but adapted forms of Nonlinear Input Models (NIMs) performed better (LN r2 = 0.61 [+/- 0.06], NIM r2 = 0.80 [+/- 0.05], with a gain change of 30% [+/-9%]). In the case of the CRH-1-GC circuit, no clear contrast adaptation was apparent, and LN models appeared to perform as well or better than NIM models.

Conclusions : These results suggest that the mechanism for gain control occurs primarily along the excitatory pathway onto ON-alpha RGCs, as contrast adaptation is not seen in the inhibitory input onto ON-alpha GCs from CRH-1 synapses. Finally, the success of NIMs relative to other models demonstrates that the mechanisms behind contrast adaptation are likely divisive (such as suppression), rather than subtractive.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

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