Fig. 2: Neural encoding of visual saliency is independent of orientation preference.

a Calcium responses of an example neuron to three types of visual stimuli: a flashing black square (10°) against a gray background (left), a flashing circular patch (10°) with horizontal (middle) or vertical (right) sinusoidal gratings against an orthogonal background. The patches were displayed at each of the 4 × 6 locations. Gray shade indicates the SD across 5 trials. Blue and red arrows mark the onset and offset of visual stimuli, respectively. The red dashed ellipse represents the outline of the fitted RF with a 2D Gaussian at half maximum. Red lines indicate the baseline activity without visual stimulation. Scale: 30% ΔF/F₀, 1 s. b Violin plots for response amplitudes to SFGs with the patch at different distances from the RF center (colored bars), as well as amplitudes to the background (gray bars) for both excitatory (N = 1531) and inhibitory (N = 2915) neurons. Red circles denote the RF. c Response amplitude to SFGs and backgrounds, grouped by the orientation preference of the background. d Histograms of SI for excitatory (Pref: 0.15 ± 0.26; Orth: 0.39 ± 0.26) and inhibitory (Pref: 0.17 ± 0.28; Orth: 0.41 ± 0.29) neurons. Cyan dashed lines mark the 0. e The percentage of orientation-selective neurons (OSI ≥ 0.25) in both non-saliency-encoding (SI ≤ 0, left) and saliency-encoding (SI > 0, right) populations. f Violin plots for the difference in response amplitudes evoked by SFGs with the preferred and orthogonal backgrounds for saliency-encoding neurons, plotted against different levels of orientation selectivity. Low: OSI < 0.25; Medium: 0.25 ≤ OSI < 0.5; High: OSI ≥ 0.5. The means of the three groups are the same: one-way ANOVA, p = 0.15 for excitatory neurons, N = 637, 309, 98; p = 0.44 for inhibitory neurons, N = 1087, 698, 160.