Vergence velocity sensitivity of SOA neurons. A: peak firing rate as a function of peak vergence velocity during saccade-vergence for a vergence velocity-sensitive near-response cell. Each point represents the peak values recorded during an individual converging or diverging saccade made while the unit was recorded. This plot includes horizontal, vertical, and oblique saccade directions. Negative values indicate divergence. The blue line is the least-squares regression for movements in the cell’s preferred direction: convergence. B: regression lines for preferred (on-direction) and nonpreferred (off-direction) saccade-vergence movements for all cells. For near-response cells, the preferred direction is convergence whereas the preferred direction of far-response cells is divergence. C–F: perimovement histograms from 2 near-response cells, one with strong vergence-velocity sensitivity (C, D) and one with weak sensitivity to vergence velocity (E, F). C and E: perimovement histograms for converging saccades. D and F: perimovement histograms for diverging saccades. From top to bottom are: spike rasters, normalized perimovement histogram, horizontal eye position (left, blue; right, red), vertical eye position (purple), and vergence angle (horizontal left eye position minus horizontal right eye position; green), shown magnified 10×. Notice that eye movements are shown from many directions for each panel, indicating the activity is not related to conjugate eye movement parameters or the movement of either eye. Also note that both the strongly and weakly velocity-sensitive cells pause their firing during saccades with off-direction vergence movements.