Indiscriminate inhibitory connectivity generates broad inhibition and temporally off-phase modulated gE and gI to drifting gratings. A, Plot of cell body locations of simulated neurons in a section of cortex. Black circles represent excitatory neurons; blue, inhibitory neurons. Red star indicates the example postsynaptic cell used in this figure. Circles with an “X” inside are functionally connected (presynaptic) to the postsynaptic cell. Light black and blue regions denote the areas from which excitatory and inhibitory presynaptic cells were drawn. Only excitatory neurons whose RFs correlate >0.5 with the postsynaptic cell were considered functionally connected. Layer 4 borders indicated by dashed lines. Green boxes and letters indicate cells whose RFs are shown in B and are indicated in C. B, 2D and 1D RFs of the 5 boxed cells in A. RFs represent bright − dark V_m responses. RFs are displaced for clarity but in fact overlap when aligned to background grids. The RFs shift along the azimuth by a factor of 0.5 RF widths/1 mm of horizontal cortex. C, 1D RFs of the excitatory (left) and inhibitory (right) cells presynaptic to the example cell. RFs are ordered by horizontal location in cortex, which correlates with RF location in visual space. D, Summed presynaptic responses of excitatory (red, left) and inhibitory (blue, right) cells to bright and dark stimuli. Dashed lines are raw values, solid lines are Gaussian fits. 1D RF of the postsynaptic cell is shown below each plot. E, SDs of Gaussian fits of gE and gI for n = 157 cells. F, Distribution of gI centers in response to bright (light gray) or dark (black) stimuli. G, Simulated response of the example cell to a drifting grating stimulus, computed as in Figure 5. H, Distribution of gE–gI phase shifts from n = 157 cells. ***p < 0.001.