Figure 7.

PVA target tracking is a function of target size and speed. A, B, LN network tracking for small (A) and large (B) targets. Speed is shown in different colors. Black line is the zero error contour. Points above the black line overpredict target location, and points below the black line underpredict. C, D, LfN network, for the motion patterns show in A and B. E, Experimentally measured fast-OFF cell population shows the same size and speed tracking dynamics as simulated LfN networks (C). F, Fast-OFF cell PVA estimates from experimental data show that for a fixed speed, a larger target (red, cyan) is always tracked with more extrapolation than a smaller target (green, purple). Likewise, slower targets (red, green) are tracked with more extrapolation than faster targets (cyan, purple). The ripple seen at low speeds results from the slight inhomogeneity in receptive field coverage between the peaks of adjacent receptive fields. At higher speeds, the target crosses these areas quickly enough that the coverage irregularities are not noticed.