Applying Super-Resolution and Tomography Concepts to Identify Receptive Field Subunits in the Retina
Fig 4
(A) Average F-score (over 1000 instantiations) versus number of subunits for the default parameters (blue, optimal for ten subunits) and for parameters adjusted for each number of subunits (red). (B) Optimal stripe width w and optimal surround factor s, depending on number of subunits. (C) Optimal position smoothing σpos and optimal angle smoothing σang. w and σpos in (B) and (C) were obtained by scaling with the number of subunits (rounded to an accuracy of 0.2 and 0.1, respectively), and s and σang were kept constant. (D) Subunit detection performance (F-score) depending on the ratio of the number of stripe positions versus angles for fixed total numbers of stripe presentations (green: 2160, default; red: half of the default; blue: double the default) and for different numbers of subunits N, using corresponding optimal parameters. Black cross marks the default scenario of ten subunits, 60 stripe positions, and 36 stripe angles. (E) Same as (D) but with the absolute number of stripe positions on the x-axis, up to a maximum of 100 positions. (F) Same as (D) but with the absolute number of stripe angles on the x-axis, up to 100 angles. (G) Subunit detection performance depending on measurement time for different numbers of subunits N, each with optimal parameters. Dashed horizontal line marks a threshold of 0.8. (H) Measurement time required to pass the 0.8 threshold in (G) depending on the number of subunits. (I) Exemplary subunit layout (left) consisting of 50 subunits, reconstructed with noise-free rate responses (center) and spike responses (right). Ricker stripes were presented at 89 positions (required minimum number according to scaling described in main text) and with 202 angles, equating to 3 hours of stimulation. Stripe and analysis parameters were scaled as before, but with a reduced angle smoothing of σang = 2°. (J) Left: Sample subunit layout with an added temporal filter to simulate responses to spatiotemporal stimuli. Center: Spatial filters from spike-triggered clustering with locally normalized L1 regularization of the sample layout’s responses to 30 minutes of coarse binary white noise. Stimulus pixels had a size of 4x4 simulated screen pixels. Red pixels denote positive values, blue pixels negative values, with each filter normalized to its absolute maximum. Right: Spike-triggered clustering with simulated responses to ten hours of fine white noise (2x2 screen pixels).