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Paul R Martin, Calvin Eiber, Alexander Pietersen, Natalie Zeater, Samuel Solomon; Chromatic and achromatic response properties of blue-on cells in marmoset lateral geniculate nucleus.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1613.
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In retina of diurnal primates, the small bistratified ganglion cell type shows "blue-on/yellow-off" receptive field properties as consequence of on-type input originating in short-wave sensitive (S) cones and off-type input originating in medium/long-wave sensitive (ML) cones (Dacey and Lee, Nature, 1994). Responses to achromatic stimuli in blue-on cells in retina, and responses of blue-on cells in lateral geniculate nucleus, are assumed to be linearly proportional to summed activity of the S-cones within the receptive field, less summed activity of the ML cones within a corresponding region. We tested this hypothesis.
Extracellular recordings of isolated unit responses to cone-selective and achromatic drifting gratings were made in Sufentanil-anesthetised marmosets. Single-Gaussian and Difference-of-Gaussian receptive fields were fit to spatial frequency tuning curves (N=45 cells) and contrast tuning curves (N = 22). A predicted achromatic spatial tuning curve was generated from the S- and ML-cone-isolating gratings. Akaike information criterion was applied to identify the best spatial receptive field model.
The best spatial model for 28 cells comprised single-Gaussian fields in each of S and ML subunits. Other cells required difference-of-Gaussians in S and/or ML subunits. The prediction error for the achromatic data was less than 5 impulses/s in 70% of the cells. Analysis of contrast tuning curves shows that the achromatic response is attributable to less-than-180 degrees phase delay between ML and S subfields (mean 171.4 deg. [9.5 ms at 5 Hz]; s.d. 21.7 deg [ 0.01 ms])
A linear sum of opponent cone inputs with distinct response latency explains achromatic responses in blue-on cells. About 60% of blue-on cells show overlapping ("Type II") S and ML subfields; the remainder show more complex spatial properties.
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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