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Testing a simplified method for measuring velocity integration in saccades using a manipulation of target contrast.

Etchells PJ, Benton CP, Ludwig CJ, Gilchrist ID - Front Psychol (2011)

Bottom Line: Observers generated saccades to one of two moving targets which were presented at high (80%) or low (7.5%) contrast.The extent to which the saccade endpoint can be accounted for as a weighted combination of the pre- or post-step velocities allows for identification of the temporal velocity integration window.Our results show that the temporal integration window takes longer to peak in the low when compared to high contrast condition.

View Article: PubMed Central - PubMed

Affiliation: School of Experimental Psychology, University of Bristol Bristol, UK.

ABSTRACT
A growing number of studies in vision research employ analyses of how perturbations in visual stimuli influence behavior on single trials. Recently, we have developed a method along such lines to assess the time course over which object velocity information is extracted on a trial-by-trial basis in order to produce an accurate intercepting saccade to a moving target. Here, we present a simplified version of this methodology, and use it to investigate how changes in stimulus contrast affect the temporal velocity integration window used when generating saccades to moving targets. Observers generated saccades to one of two moving targets which were presented at high (80%) or low (7.5%) contrast. In 50% of trials, target velocity stepped up or down after a variable interval after the saccadic go signal. The extent to which the saccade endpoint can be accounted for as a weighted combination of the pre- or post-step velocities allows for identification of the temporal velocity integration window. Our results show that the temporal integration window takes longer to peak in the low when compared to high contrast condition. By enabling the assessment of how information such as changes in velocity can be used in the programming of a saccadic eye movement on single trials, this study describes and tests a novel methodology with which to look at the internal processing mechanisms that transform sensory visual inputs into oculomotor outputs.

No MeSH data available.


Related in: MedlinePlus

(A) Outline of the time course for a rightwards, step up trial. Gaussian patches start moving rightward. After some interval of time the fixation stimulus changes to an arrow, signaling that a saccade to the top patch should be made. After this, the patches step up in speed (illustrated by the double arrows). Note that patches and fixation point are not to scale, for illustration purposes. (B) The fixation stimulus. Removal of either the bottom two or top two diagonal line segments results in an arrow indicating which patch to saccade to.
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Figure 2: (A) Outline of the time course for a rightwards, step up trial. Gaussian patches start moving rightward. After some interval of time the fixation stimulus changes to an arrow, signaling that a saccade to the top patch should be made. After this, the patches step up in speed (illustrated by the double arrows). Note that patches and fixation point are not to scale, for illustration purposes. (B) The fixation stimulus. Removal of either the bottom two or top two diagonal line segments results in an arrow indicating which patch to saccade to.

Mentions: Observers were required to fixate a central diamond-shaped fixation stimulus on a computer screen whilst two Gaussian patches (SD = 0.32°) traversed horizontally across the screen, 6° above and below the midline. During the trial, the fixation point would change into either an upwards- or downwards-pointing arrow, indicating which patch the observers had to make a saccade to (see Figure 2A). On some trials, after a variable delay the speed of the patches would change. By looking at the relationship between saccade landing positions and the time of the speed changes, we can determine how the saccadic system weighs the two velocities over time. We examine the nature of this velocity integration function in two conditions: high and low-contrast.


Testing a simplified method for measuring velocity integration in saccades using a manipulation of target contrast.

Etchells PJ, Benton CP, Ludwig CJ, Gilchrist ID - Front Psychol (2011)

(A) Outline of the time course for a rightwards, step up trial. Gaussian patches start moving rightward. After some interval of time the fixation stimulus changes to an arrow, signaling that a saccade to the top patch should be made. After this, the patches step up in speed (illustrated by the double arrows). Note that patches and fixation point are not to scale, for illustration purposes. (B) The fixation stimulus. Removal of either the bottom two or top two diagonal line segments results in an arrow indicating which patch to saccade to.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108583&req=5

Figure 2: (A) Outline of the time course for a rightwards, step up trial. Gaussian patches start moving rightward. After some interval of time the fixation stimulus changes to an arrow, signaling that a saccade to the top patch should be made. After this, the patches step up in speed (illustrated by the double arrows). Note that patches and fixation point are not to scale, for illustration purposes. (B) The fixation stimulus. Removal of either the bottom two or top two diagonal line segments results in an arrow indicating which patch to saccade to.
Mentions: Observers were required to fixate a central diamond-shaped fixation stimulus on a computer screen whilst two Gaussian patches (SD = 0.32°) traversed horizontally across the screen, 6° above and below the midline. During the trial, the fixation point would change into either an upwards- or downwards-pointing arrow, indicating which patch the observers had to make a saccade to (see Figure 2A). On some trials, after a variable delay the speed of the patches would change. By looking at the relationship between saccade landing positions and the time of the speed changes, we can determine how the saccadic system weighs the two velocities over time. We examine the nature of this velocity integration function in two conditions: high and low-contrast.

Bottom Line: Observers generated saccades to one of two moving targets which were presented at high (80%) or low (7.5%) contrast.The extent to which the saccade endpoint can be accounted for as a weighted combination of the pre- or post-step velocities allows for identification of the temporal velocity integration window.Our results show that the temporal integration window takes longer to peak in the low when compared to high contrast condition.

View Article: PubMed Central - PubMed

Affiliation: School of Experimental Psychology, University of Bristol Bristol, UK.

ABSTRACT
A growing number of studies in vision research employ analyses of how perturbations in visual stimuli influence behavior on single trials. Recently, we have developed a method along such lines to assess the time course over which object velocity information is extracted on a trial-by-trial basis in order to produce an accurate intercepting saccade to a moving target. Here, we present a simplified version of this methodology, and use it to investigate how changes in stimulus contrast affect the temporal velocity integration window used when generating saccades to moving targets. Observers generated saccades to one of two moving targets which were presented at high (80%) or low (7.5%) contrast. In 50% of trials, target velocity stepped up or down after a variable interval after the saccadic go signal. The extent to which the saccade endpoint can be accounted for as a weighted combination of the pre- or post-step velocities allows for identification of the temporal velocity integration window. Our results show that the temporal integration window takes longer to peak in the low when compared to high contrast condition. By enabling the assessment of how information such as changes in velocity can be used in the programming of a saccadic eye movement on single trials, this study describes and tests a novel methodology with which to look at the internal processing mechanisms that transform sensory visual inputs into oculomotor outputs.

No MeSH data available.


Related in: MedlinePlus