Figure 4.

Ramp and curvature indices for the neurons. The ramp index is positive for ramp-up tuning (e.g., the neuron in Fig. 3, top row, is depicted in A as an x) and negative for ramp-down tuning. The curvature index is positive for concave tunings (the neuron in Fig. 3, middle row, is shown in B with a square) and negative for convex tunings. A neuron with hybrid tuning, both ramp up and concave, is shown with a cross in B. A, B, For all neurons tested in the parallel (A) and perpendicular (B) conditions, individual neurons with significant translation tuning as determined by the maximum–minimum index (see Fig. 5) are shown with bold outlines or the aforementioned symbols. C, D, The neurons with significant translation tuning are segregated into visual (green) and visuomovement (purple) types for the parallel condition (C) and the perpendicular condition (D).