Optimal Control of Saccades by Spatial-Temporal Activity Patterns in the Monkey Superior Colliculus
Figure 7
Burst shapes depend on planned movement.
Temporal firing patterns of a neuron during small and large saccades for which the cell fired about same number of spikes. A–C) Spike density (color code) as a function of time for saccades of different amplitude in the preferred direction of the cell. Data are sorted by saccade amplitude. Tick marks indicate spike-count windows. Gray traces: average eye position, eye velocity and spike density functions for small, 6° saccades (n = 5). Black traces: averaged data for large, 17° saccades (n = 16) for which the cell fired about the same number of spikes (Ns≅25). Inset in A: running average of the number of spikes as a function of saccade amplitude. Vertical line segments: amplitude range of saccades included in the two datasets. Horizontal line segments: mean±SD of the corresponding spike counts. Insets B and C: schematic drawing of population activity relative to the recording site. D) Location and extent of the movement field (color code) plus saccade endpoints (symbols). E) Normalized spike density functions for the two saccade vectors. Note that the shapes of the bursts for small saccades (light-gray traces) and large saccades (dark-gray traces) are clearly different. Peak firing rates occurred at about the same instant relative to movement onset regardless of the movement amplitude, but burst durations were shorter and peak firing rates were higher when the cell took part in the small saccades than when it participated in the large saccades.