Fig. 2

V2 feedback controls RF size. a Spatial summation curves for two example V1 cells recorded with (green) and without (black) laser stimulation. Gray area in left panel: proximal surround. Insets: PSTHs (Bottom; due to the smoothing filter used, response onset starts at time zero) and raster plots (Top) measured at the stimulus diameters indicated by the red circles in the respective size-tuning curves. Green horizontal line: laser-on time. Two additional example cells are shown in the insets of panels f and g. b–e Mean sRF size (diameter at peak response of empirically measured spatial summation curve) with and without laser stimulation for: b All cells (LEFT; n = 33); RIGHT: Cell-by-cell percent change in sRF size across the entire cell population. Downward and upward stem: decreased and increased sRF size, respectively. Arrow: mean. c Only cells showing increased sRF size with laser stimulation (n = 25; mean sRF diameter ± s.e.m. no laser vs. laser: 1.12 ± 0.08° vs. 1.93 ± 0.08°). d Only cells showing both increased sRF size and peak response with laser stimulation (n = 12; 1.14 ± 0.08° vs. 2.04 ± 0.20°). e Mean sRF size for all cells (as in b), but grouped according to layer. SG: supragranular; G: granular; IG: infra-granular. f–g Scatterplots of sRF diameter with and without laser stimulation for sRF diameter derived directly from the empirically measured summation curves (f), or from the model curves fitted to the summation data (g), as indicated in the insets above each scatterplot. Insets in f and g show the size tuning curve of two additional example cells. The summation data for the cell in g are fitted with the ROG model. Arrows in insets in f and g indicate the sRF diameters. Arrows in scatterplots: means. Dashed line in f–g: unity line. Here and in all remaining figures error bars are s.e.m