Spatial Accuracy of Predictive Saccades Determines the Performance of Continuous Visuomotor Action (original) (raw)
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Annals of the New York Academy of Sciences, 2005
The metrics and dynamics of saccades to stationary and moving targets were observed in monkeys (Macaca mulatta). To isolate the effects of target speed on the saccade from contributions of smooth pursuit, saccade velocity was corrected for intrasaccadic pursuit velocity on a trial-by-trial basis prior to analysis. The effects of presaccadic retinal error and target speed on the saccadic velocity profile were determined by analyzing the partial correlations computed as a function of time after saccade onset. The main results are: (1) Saccade amplitude is determined not only by the retinal error sampled before the saccade, but also by the speed of the target during the latency period. (2) The dynamics of saccades, even if compensated for smooth-pursuit components, differ between forward-and backward-moving targets. (3) Whereas the presaccadic retinal error affects the eye velocity throughout the saccade, target speed has no effect before peak velocity. These results are discussed in the context of current models of saccade generation and their physiological substrates, in particular the role of the cerebellum in the local feedback loop.
The accuracy and precision of saccades to small and large targets
Vision research, 1995
Subjects made saccades to point and spatially-extended targets located at a randomly-selected eccentricity (3.8-4.2 deg) under conditions designed to promote best possible accuracy based only on the visual information present in a single trial. Saccadic errors to point targets were small. The average difference between mean saccade size and target eccentricity was about 1% of eccentricity. Precision was excellent (SD = 5-6% of eccentricity), rivaling the precision of relative perceptual localization. This level of performance was maintained for targets up to 3 deg in diameter. Corrective saccades were infrequent and limited almost exclusively to the point targets. We conclude that the saccadic system has access to a precise representation of a central reference position within spatially-extended targets and that, when explicitly required to do so, the saccadic system is capable of demonstrating remarkably accurate and precise performance.
Human Movement Science, 2004
The present experiment examined the one-target advantage (OTA) with regard to saccadic eye movements. The OTA, previously found with manual pointing responses, refers to the finding that movements are executed faster when the limb is allowed to stop on the target compared to the situation where it has to proceed and hit a second target. Using an adapted limb movement OTA task, saccades of 5°and 15°were made to (a) a single target (one-target), (b) one target and immediately to another target without a change in direction (two-target-extension), and (c) one target and immediately back to the start location (two-target-reversal). Unlike manual movements, the movement times for the initial saccade in the two-target-extension condition were not prolonged compared to either of the other two conditions. Moreover, this pattern of results was found for both the shorter and longer amplitude saccades. The results indicate that the OTA does not occur in the oculomotor system and therefore is not a general motor control phenomenon.
Journal of Vision, 2014
This study analyzes how human participants combine saccadic and pursuit gaze movements when they track an oscillating target moving along a randomly oriented straight line with the head free to move. We found that to track the moving target appropriately, participants triggered more saccades with increasing target oscillation frequency to compensate for imperfect tracking gains. Our sinusoidal paradigm allowed us to show that saccade amplitude was better correlated with internal estimates of position and velocity error at saccade onset than with those parameters 100 ms before saccade onset as head-restrained studies have shown. An analysis of saccadic onset time revealed that most of the saccades were triggered when the target was accelerating. Finally, we found that most saccades were triggered when small position errors were combined with large velocity errors at saccade onset. This could explain why saccade amplitude was better correlated with velocity error than with position error. Therefore, our results indicate that the triggering mechanism of head-unrestrained catch-up saccades combines position and velocity error at saccade onset to program and correct saccade amplitude rather than using sensory information 100 ms before saccade onset.
Saccades to remembered targets: The effects of saccades and illusory stimulus motion
Vision Research, 1998
In 10 human subjects, we measured the accuracy of saccades to remembered locations of targets that were flashed on a 20 x 30 deg random dot display, while they tracked a spot of light that stepped between three vertical locations. The background was either stationary or stepping horizontally in synchrony with vertical motion of the spot of light, a condition that induced a strong illusion of diagonal target motion. Memory-guided saccades were less accurate horizontally, but not vertically, when the background moved compared with when it was stationary. The horizontal component of memory-guided saccades correlated better with the position of the background when the target was flashed than with the position of the background at the end of the memory period. We conclude that the visual illusion corrupted the working memory of target location, but had a lesser effect on the estimate of gaze at the end of the memory period, which seemed to depend more on extraretinal signals. Published by Elsevier Science Ltd.
Enhanced Tactile Performance at the Destination of an Upcoming Saccade
Current Biology, 2002
saka and Wurtz [12], who reported presaccadic enhancement to auditory stimuli. In particular, they noted United Kingdom 2 Department of Psychology that some neurons in the substantia nigra pars reticulata significantly reduce their firing rate after exposure to University of South Carolina South Carolina contralateral auditory stimuli. This reduced firing rate is sustained after the offset of brief auditory stimuli only in trials in which a saccade is made to the location of the auditory stimuli. This work demonstrates that upcoming Summary eye movements can modulate neural firing to nonvisual stimuli. However, it is also important to note that regions Previous work has demonstrated that upcoming sacof both the parietal cortex and the superior colliculus cades influence visual [1, 2] and auditory [3] perforare sensitive to visual, auditory, and tactile stimuli [13], mance even for stimuli presented before the saccade although investigators have yet to specifically look for is executed. These studies suggest a close relationauditory or tactile saccadic enhancement in these reship between saccade generation and visual/auditory gions. attention. Furthermore, they provide support for Riz-To date, there are no reports that tactile performance zolatti et al.'s [4, 5] premotor model of attention, which is improved by upcoming saccades. In a thorough resuggests that the same circuits involved in motor proview of the literature on crossmodal spatial attention, gramming are also responsible for shifts in covert ori-Driver and Spence [14] presented a schematic diagram enting (shifting attention without moving the eyes or showing all the investigated links in exogenous covert changing posture). In a series of experiments, we demattention; however, their diagram of recent research
The effect of a temporary absence of target velocity information on visual tracking
Journal of Vision, 2004
College of Optometry Experiments with the Rashbass 'step-ramp' paradigm have revealed that the initial catchup saccade that occurs near pursuit onset uses target velocity as well as position information in its programming. Information about both position and motion also influences smooth pursuit. To investigate the timing of velocity sampling near the initiation of saccades and smooth pursuit, we analyzed the eye movements made in nine 'step-ramp' conditions, produced by combining-2, 0 and +2 deg steps with-8, 0 and +8 deg/s ramps. Each trial had either no temporal gap or a 50-ms gap during which the laser target was extinguished, beginning 25, 50, 75 or 100 ms after the step. Six subjects repeated each of the resulting 45 conditions 25 times. With no temporal gap, saccades were larger in the 'step-ramp-away' than the 'step-only' condition, confirming that saccade programming incorporates ramp velocity information. A temporal gap had no effect on the accuracy of saccades on 'step-only' trials, but often caused undershoots in 'step-ramp' trials. A 50-ms gap within the first 100 ms also increased the latency of the initial saccade. Although initial pursuit velocity was unaffected by a temporal gap, a gap that started at 25 ms reliably delayed pursuit onset for ramp motion of the target toward the fovea. Later gaps had a minimal effect on initial pursuit latency. The similar timing of the temporal gaps in target motion information that affect the initiation of saccades and pursuit provides further behavioral evidence that the two types of eye movements share pre-motor neural mechanisms.
Influence of arm movements on saccades in humans
European Journal of Neuroscience, 2000
When reaching for an object we usually look at it before we touch it with the hand. This often unconscious eye movement prior to the arm movement allows guiding of the ®nal part of the hand trajectory by visual feedback. We examined the temporal and spatial coordination of this control system by psychophysical measurements of eye and arm movements of naive human subjects looking or looking and pointing as fast as possible to visual targets in physical and virtual-reality setups. The reaction times of saccades to a step-displaced target were reduced, and the number of corrective saccades decreased, when the subject had to produce a corresponding simultaneous hand movement to the same target. The saccadic reaction time was increased when saccade and hand movement went in opposite directions. In a double-step task the reaction time for the second saccade was longer than for the ®rst. Co-use of the hand leads to an additional increase of saccadic reaction time. Taken together this study shows an improvement in initial saccades if they are accompanied by hand movements to the same target. This effect might ensure that the reach target is foveated early and accurately enough to support the visual feedback control of the hand near the target. Longer reaction times for the second saccade to double-step displaced targets might re¯ect a saccadic refractory time intensi®ed by simultaneous arm movements. These results are discussed in the light of recent ®ndings from our laboratory on saccade-and reach-related neurons in the superior colliculus of macaque monkeys.