Interspike intervals within retinal spike bursts combinatorially encode multiple stimulus features
Fig 6
ISI analysis of bursts elicited by natural scene stimulation.
(A) Responses of a single ganglion cell. (Right) Raster plots. The colored dots indicate 3-spike bursts. The gray dots represent remaining spikes. (Left) Image frames acquired at −60 ms relative to the average timing of the first spike in bursts. White ellipses show receptive field centers determined by reverse correlation and Gaussian fitting. Bar, 1 mm. (B–D) Analyses performed using light intensity at the receptive field center. (B) Analysis of 2-spike bursts of a single cell. The thick black line indicates the average of all stimulus sequences preceding 2-spike bursts (2-BTA). The thick colored lines indicate the average of stimulus sequences preceding 2-spike bursts with different intraburst ISIs. The thin lines indicate SEM values calculated across bursts. (C) Population analysis of the deviation from 2-BTA. For each cell, the deviation from 2-BTA was calculated by subtracting 2-BTA from the average stimulus sequence preceding 2-spike bursts with the longest and shortest 50% of intraburst ISIs. The thick lines indicate the deviation from 2-BTA averaged across the 13 cells that generated more than 800 2-spike bursts (yellow, longest ISIs; blue, shortest ISIs). The thin lines indicate the SEM values calculated across the cells. (D) Deviation from 3-BTA. For each cell, the deviation from 3-BTA was calculated by subtracting 3-BTA from the average stimulus sequence preceding 3-spike bursts with the burst phase within a specific range. The thick lines indicate the deviation from 3-BTA averaged across the 8 cells that generated more than 1000 3-spike bursts. The thin lines show SEM values calculated across the cells. The arrows indicate the first peak before the first spike in bursts.