Optimal Control of Saccades by Spatial-Temporal Activity Patterns in the Monkey Superior Colliculus
Figure 2
Movement field scan of a saccade-related SC neuron illustrating the presence of signal-dependent noise.
A) Spike density (color code) as a function of time for saccades in and near the center of the movement field, with trials sorted by amplitude of the movement (amplitude scan; fixed direction Φ≅237°). Tick marks indicate spike-count windows (20 ms before onset to 20 ms before offset of the saccade). Superimposed is the average eye position of saccades towards the movement field center. Spike counts (open symbols) are displayed as running averages across 6° wide bins. Error bars indicate the trial-to-trial variability in spike counts (±1 SD). B) Same for a direction scan through the center of the movement field (fixed amplitude R≅13°). Spike counts were averaged across 13° wide bins. Average velocity profile of saccades towards the center is superimposed. C) Spatial extent of the movement field together with the endpoints of saccades (re. to initial fixation, +) included in the amplitude and direction scan. Color code: movement field description (Methods, Eq. 3) of the number of spikes in the burst as function of saccade amplitude and direction. Contour lines are drawn at [0.5, 1.0, 1.5 and 2.0]⋅σmf. D) Spike-count standard deviations as a function of mean number of spikes in the burst. Linear regression line (solid) was calculated from the pooled data of the amplitude (squares) and direction (circles) scans.