Figure 1.
Simplified conceptual scheme of saccade generation.
Excitatory projections from the superior colliculus (SC) drive the saccadic burst generator (BG) in the brainstem. Activity from the BG is regulated by a feedback loop to preserve saccade accuracy. Within the brainstem a mutual inhibitory network exists between the omnipause neurons (OPNs) and the BG. Blinks have been shown to affect the brainstem in a manner that suppresses OPN activity. In addition, we incorporate mutual inhibitory effects between the blink and the SC in order to comment on the behavioral correlations seen within our data. Evidence supports the existence of such interaction, although the exact neural correlate is unknown.
Figure 2.
Microstimulation with blink examples.
Representative examples of spatial trajectories (horizontal vs. vertical eye positions) shown from the four animals evoked by sub-optimal microstimulation. In all plots, the blue trajectories represent stimulation-evoked reduced amplitude saccades without blinks. Note: mean metrics (horizontal, vertical) evoked by suprathreshold stimulation for monkey 1 (−20.6, 8.5), monkey 2 (29.9, 0), monkey 3 (−23.2, −4.5), monkey 4 (34.8, 5.3). The traces in the other colors represent movements evoked when stimulation was combined with a puff-evoked blink. All traces are offset to the origin with each trace being plotted from stimulation onset to movement offset. Note: Black diamonds superimposed on the trajectories indicate where the blink occurred relative to stimulation onset.
Figure 3.
An alternate representation of the data illustrated in Figure 2. Horizontal and vertical eye velocity is plotted as a function of time for stimulation-evoked saccades with and without blink perturbations. All traces are aligned on saccade onset. All other configurations are the same as in Figure 2.
Figure 4.
The scatter plots compare the duration (left), peak velocity (middle) and average velocity (right) of saccades evoked from stimulation-only trials and stimulation-with-blink trials. Each dot represents the mean value from one stimulation site, and the error bars represent one standard deviation. The four colors correspond to the four animals, as indicated in the key.
Figure 5.
Comparison of radial amplitude.
Comparison of mean radial amplitudes for stimulation-evoked saccades without and with a puff-evoked blink. Green dots represent values from monkey 1; cyan, monkey 2; red, monkey 3; gray, monkey 4. Error bars represent one standard deviation from the mean; solid line marks unity slope. The majority of stimulation sites lie above the unity line, indicating an increase of saccade amplitude due to the blink-saccade interaction.
Figure 6.
Distribution of dysmetria induced by the blink perturbation.
Each point represents the horizontal and vertical endpoint position of a stimulation-with-blink movement after subtraction of the endpoint of the mean stimulation-only movement obtained from the same stimulation site. Each dot represents one trial, and data from all trials across all stimulation sites are included in the plot. Green squares represent data for monkey 1; cyan triangles, monkey 2; red circles, monkey 3; gray diamonds, monkey 4. Note that the absolute values of endpoints were used to standardize alignment for movements in opposing directions.
Figure 7.
Correlation with BREM kinematics.
The peak velocity of BREM movements versus the change in mean radial amplitude of stimulation-evoked saccades colliding with a puff-evoked blink. Green squares correspond to monkey 1; cyan triangles, monkey 2; red circles, monkey 3; gray diamonds, monkey 4.