Interspike intervals within retinal spike bursts combinatorially encode multiple stimulus features
Fig 3
Intraburst ISIs of 2-spike bursts encode an oscillatory component of the visual input.
(A–G) Data from the cell shown in Fig 1. (A) Raster plot. The colored lines represent 2-spike bursts. The short gray lines are the remaining spikes. The gray continuous line shows the normalized light intensity of the stimulus (the mean and SD are 0 and 1, respectively). Event IDs are shown. (B and C) Intraburst ISIs of 2-spike bursts (B) and the average and SD of the spike number (C) of the four events shown in (A). (D) Relationship between 2-spike burst ISIs and the mean spike number. Each dot represents an event with at least one 2-spike burst. The horizontal and vertical axes represent the mean ISI of 2-spike bursts and the mean spike number, respectively. The correlation was −0.15 for this cell. (E) Stimulus sequences preceding 2-spike bursts with an intraburst ISI of < 6.0 ms (top) and > 16.0 ms (bottom) are aligned with respect to the first spike in the bursts. (F) 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 the stimulus sequences preceding 2-spike bursts with different intraburst ISIs. The thin lines indicate the SEM values calculated across bursts. (G) The thick yellow and blue lines indicate the deviations from 2-BTA, i.e., the average of the stimulus sequence preceding 2-spike bursts with the longest and shortest 50% of intraburst ISIs, respectively, from which the 2-BTA was subtracted. The thin lines indicate SEM values calculated across bursts. (H) Population analysis. The thick lines indicate the deviation from 2-BTA represented by the thick lines in (G) averaged among 19 cells that generated at least 1500 2-spike bursts. The thin lines represent SEM values calculated among the cells. (I) Analysis of sD2,2-spike, the stimulus projected onto the deviation from the 2-BTA and collected at the time points of all 2-spike bursts and normalized to have a mean = 0 and a SD = 1. The dashed line shows P(sD2,2-spike) averaged across the 19 cells. The thick solid lines are the probability distribution of sD2,2-spike at 2-spike bursts with short, medium, and long ISIs, P(sD2,2-spike|0−10% ISI), P(sD2,2-spike|45−55% ISI), and P(sD2,2-spike|90−100% ISI), respectively, averaged across the 19 cells. The thin lines are the SEM calculated across the cells. (J) Similar to (I), calculated for s3−1,2-spike, the stimulus projected onto 3-BTA−1-BTA.