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Modeling spatial contrast sensitivity in responses of primate retinal ganglion cells to natural movies

Fig 2

Examples of the effect of local spatial contrast on responses to natural scenes.

A: Illustration of the stimulus processing to obtain I_mean and LSC by applying the filters of a sample OFF parasol cell (1st column) to the stimulus (2nd column, exemplified here by a single frame) to obtain a temporally convolved stimulus (3rd column, overlaid with the 3- contour of the spatial filter), from which the weighted light intensity signal (4th column) and the weighted spatial contrast (5th column) are extracted. The two rows correspond to two separate stimulus segments. The plots of the light-intensity and spatial-contrast signals display the results of the pixel-wise computation as indicated by the formulas at the top (where u_s denotes the spatial filter and h_s the temporally convolved stimulus frame), with the final values given in the lower left of the plots. The time course of the Z-scored light-intensity and spatial-contrast signals (top) along with the corresponding measured firing rates (bottom) of the sample cell are shown in the 6th column, with the light gray region highlighting the time window of presentation of the analyzed stimulus frame for which the I_mean and LSC values in columns 4 and 5 were calculated. B: Same as A, but for a sample OFF midget cell. Both cells are the same as in Fig 1B–F. Frames of the stimulus taken from an open-source movie licensed under CC BY 3.0 [28].

doi: https://doi.org/10.1371/journal.pcbi.1014157.g002