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Bart Gerard Borghuis, Charles P. Ratliff; The rates of visual information encoding in parallel retinal bipolar cell pathways. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2972.
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© ARVO (1962-2015); The Authors (2016-present)
Bipolar cells (BCs) in the mammalian retina comprise about fourteen types. With few exceptions, all types sample from the same cone photoreceptors, yet their visual responses differ. While BC pathways exemplify parallel neural circuit architecture the extent of differences in their visual receptive fields and rates of visual information encoding remain unclear.
We used 2P fluorescence-guided whole-cell electrophysiology, white noise stimulation, and LN model analysis to measure receptive fields, and information theoretic methods to compute rates of information encoding in identified BC types in the whole-mount mouse retina. We compared information rates at the level of the excitatory synaptic input and membrane voltage across types, and related information rates of BCs to those of identified ganglion cells.
Visual receptive fields of BC types 1, 4, and 6 and 7 showed minor spatial differences but substantial temporal differences. Information rates at the level of the membrane voltage response differed between types, from ~25 bits/s in type 7 to 45-50 bits/s in type 3a and 6 BCs. Information rates of the excitatory input exceeded those of the membrane voltage response by up to 45%, indicating that inhibition removes information, potentially reducing redundancy across types. α-Type ganglion cells showed similar information rates as BCs, 33–43 bits/s, whereas in δ-type ganglion cells the rate was lower, ~16 bits/s.
BC types differ in their rate of visual information encoding both at the level of excitatory input and membrane voltage response. The differences are modest (about 2.5-fold), and smaller than expected based on reported differences in synaptic response properties.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
1. BC spatio-temporal receptive fields. (A) 2P-guided BC recording. (B) Receptive fields were measured by reverse-correlating a white noise stimulus and evoked response. (C) Receptive field maps (left) and Gaussian fits (right); r, radius at 2σ. (D) Temporal receptive fields of the cells in C. BC type 1 has longer time-to-peak (arrowhead) and response persistence (arrow).
2. Rates of visual information encoding in identified retinal neuron types. (A) BC response to 50 white noise stimulus repeats. (B) Information rates were calculated from the signal-to-noise ratio across temporal frequencies. (C) Information rates of identified BCs; OFF-α ganglion cell and unidentified amacrine cell included for comparison.
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