Correlation of two types of suppression with surround suppression. A, Schematic of the cascading relationship between the input layer (L4C) and output layer (L2/3). Stimuli were drifting sinusoidal gratings with different radius. Arrow thickness represents the strength of two types of suppression and excitation. B, Examples of individual tuning curves measured with drifting gratings of varying radius. Red curves indicate fits to the data (black dots) using the difference between two Naka–Rushton functions. Gray line indicates the spontaneous rate of firing. The example site was located in layer 2/3. C, D, Relationship between surround suppression and two types of suppression (C, FS; D, SS). Scatter plot for all sites of layer 4C. Strength of suppression defined as averaged strength from 0 to 200 ms. E, F, Similar to C, D but for all sites of layer 2/3.