Detecting monosynaptic connections with spike cross-correlograms (CC). A, STAs revealing EPSPs for three ON-center LGN cells connected to the same V1 cell. Bottom, 20% RF contours. Unlabeled elliptical contour, is the V1 RF. B, Corrected LGN-V1 CCs (see Materials and Methods) for the three connected LGN cells. Only cell A has a significant peak with monosynaptic latency. C, CCs overlaid with jittered CCs (red) between connected LGN cells. The peak at positive lag for the CC between LGN cell B and A indicates that on average cell A spikes after cell B.