The Smooth Pursuit System

2008 ◽  
Author(s):  
Agnes Wong
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Smooth Pursuit ◽  
Moving Object ◽  
Smooth Pursuit Eye Movements ◽  
En Bloc ◽  
Pursuit Eye Movements ◽  
Ocular Reflex ◽  
Suitable Target ◽  
Stationary Background

Smooth pursuit consists of conjugate eye movements that allow both eyes to smoothly track a slowly moving object so that its image is kept on the foveae. For example, smooth pursuit eye movements are used when you track a child on a swing. Only animals with foveae make smooth pursuit eye movements. Rabbits, for instance, do not have foveae, and their eyes cannot track a small moving target. However, if a rabbit is placed inside a rotating drum painted on the inside with stripes so that the rabbit sees the entire visual field rotating en bloc, it will track the stripes optokinetically. Humans have both smooth pursuit and optokinetic eye movements, but pursuit predominates. When you track a small, moving object against a detailed stationary background, such as a bird flying against a background of leaves, the optokinetic system will try to hold your gaze on the stationary background, but it is overridden by pursuit. Pursuit works well at speeds up to about 70°/sec, but top athletes may generate pursuit as fast as 130°/sec. Pursuit responds slowly to unexpected changes—it takes about 100 msec to track a target that starts to move suddenly, and this is why we need the faster acting vestibulo-ocular reflex (VOR) to stabilize our eyes when our heads move. However, pursuit can detect patterns of motion and respond to predictable target motion in much less than 100 msec. Pursuit cannot be generated voluntarily without a suitable target. If you try to pursue an imaginary target moving across your visual field, you will make a series of saccades instead of pursuit. However, the target that evokes pursuit does not have to be visual; it may be auditory (e.g., a moving, beeping pager), proprioceptive (e.g., tracking your outstretched finger in the dark), tactile (e.g., an ant crawling on your arm in the dark), or cognitive (e.g., tracking a stroboscopic motion in which a series of light flashes in sequence, even though no actual motion occurs.

scholarly journals Comparison between Passively Evoked Smooth Pursuit Eye Movements and Optokinetic Ocular Reflex.

1997 ◽  
Vol 56 (5) ◽  
pp. 444-453
Author(s):  
Motoyuki Hashiba ◽  
Teruaki Hattori ◽  
Nobuhiro Watanabe ◽  
Shunkichi Baba ◽  
Hirotaka Watabe ◽  
...  
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements ◽  
Ocular Reflex

Ablation of the pursuit area in the frontal cortex of the primate degrades foveal but not optokinetic smooth eye movements

1996 ◽  
Vol 76 (1) ◽  
pp. 637-641 ◽  
Author(s):  
E. G. Keating ◽  
A. Pierre ◽  
S. Chopra
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Frontal Cortex ◽  
Frontal Lobe ◽  
Relative Motion ◽  
Smooth Pursuit ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements ◽  
Motion Detectors ◽  
Do So

1. Neural pathology which impairs foveal smooth pursuit eye movements typically also degrades optokinetic pursuit of large textures, suggesting that the two kinds of pursuit share a common circuit. This study reports an exception. After sequential bilateral ablation of the pursuit area in the frontal lobe three monkeys displayed degraded pursuit of a small foveal target but performed normally on identical measures of optokinetic pursuit. 2. A related experiment in one subject demonstrated a pursuit deficit when the foveal target moved relative to the background, but not when background and target moved together. The frontal pursuit area may specifically control pursuit of relative motion, and do so by receiving signals primarily from motion detectors in the macular part of the visual field.

Contextual Effects on Smooth-Pursuit Eye Movements

2007 ◽  
Vol 97 (2) ◽  
pp. 1353-1367 ◽  
Author(s):  
Miriam Spering ◽  
Karl R. Gegenfurtner
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Moving Object ◽  
Visual Context ◽  
Smooth Pursuit Eye Movements ◽  
Motion Direction ◽  
Pursuit Eye Movements ◽  
Motion Signal ◽  
Motion Contrast ◽  
Eye Velocity

Segregating a moving object from its visual context is particularly relevant for the control of smooth-pursuit eye movements. We examined the interaction between a moving object and a stationary or moving visual context to determine the role of the context motion signal in driving pursuit. Eye movements were recorded from human observers to a medium-contrast Gaussian dot that moved horizontally at constant velocity. A peripheral context consisted of two vertically oriented sinusoidal gratings, one above and one below the stimulus trajectory, that were either stationary or drifted into the same or opposite direction as that of the target at different velocities. We found that a stationary context impaired pursuit acceleration and velocity and prolonged pursuit latency. A drifting context enhanced pursuit performance, irrespective of its motion direction. This effect was modulated by context contrast and orientation. When a context was briefly perturbed to move faster or slower eye velocity changed accordingly, but only when the context was drifting along with the target. Perturbing a context into the direction orthogonal to target motion evoked a deviation of the eye opposite to the perturbation direction. We therefore provide evidence for the use of absolute and relative motion cues, or motion assimilation and motion contrast, for the control of smooth-pursuit eye movements.

scholarly journals Interference between smooth pursuit and color working memory

2017 ◽  
Vol 10 (3) ◽  
Author(s):  
Shulin Yue ◽  
Zhenlan Jin ◽  
Chenggui Fan ◽  
Qian Zhang ◽  
Ling Li
Keyword(s):  
Working Memory ◽  
Eye Movements ◽  
Visual Field ◽  
Spatial Attention ◽  
Smooth Pursuit ◽  
Spatial Working Memory ◽  
Smooth Pursuit Eye Movements ◽  
Match To Sample ◽  
Pursuit Eye Movements ◽  
The Relationship

Spatial working memory (WM) and spatial attention are closely related, but the relationship between non-spatial WM and spatial attention still remains unclear. The present study aimed to investigate the interaction between color WM and smooth pursuit eye movements. A modified delayed-match-to-sample paradigm (DMS) was applied with 2 or 4 items presented in each visual field. Subjects memorized the colors of items in the cued visual field and smoothly moved eyes towards or away from memorized items during retention interval despite that the colored items were no longer visible. The WM performance decreased with higher load in general. More importantly, the WM performance was better when subjects pursued towards rather than away from the cued visual field. Meanwhile, the pursuit gain decreased with higher load and demonstrated a higher result when pursuing away from the cued visual field. These results indicated that spatial attention, guiding attention to the memorized items, benefits color WM. Therefore, we propose that a competition for attention resources exists between color WM and smooth pursuit eye movements.

Chromatic Contrast Sensitivity During Optokinetic Nystagmus, Visually Enhanced Vestibulo-ocular Reflex, and Smooth Pursuit Eye Movements

2009 ◽  
Vol 101 (5) ◽  
pp. 2317-2327 ◽  
Author(s):  
Alexander C. Schütz ◽  
Doris I. Braun ◽  
Karl R. Gegenfurtner
Keyword(s):  
Eye Movements ◽  
Contrast Sensitivity ◽  
Smooth Pursuit ◽  
Optokinetic Nystagmus ◽  
Slow Phase ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Slow Eye Movements

Recently we showed that sensitivity for chromatic- and high-spatial frequency luminance stimuli is enhanced during smooth-pursuit eye movements (SPEMs). Here we investigated whether this enhancement is a general property of slow eye movements. Besides SPEM there are two other classes of eye movements that operate in a similar range of eye velocities: the optokinetic nystagmus (OKN) is a reflexive pattern of alternating fast and slow eye movements elicited by wide-field visual motion and the vestibulo-ocular reflex (VOR) stabilizes the gaze during head movements. In a natural environment all three classes of eye movements act synergistically to allow clear central vision during self- and object motion. To test whether the same improvement of chromatic sensitivity occurs during all of these eye movements, we measured human detection performance of chromatic and luminance line stimuli during OKN and contrast sensitivity during VOR and SPEM at comparable velocities. For comparison, performance in the same tasks was tested during fixation. During the slow phase of OKN we found a similar enhancement of chromatic detection rate like that during SPEM, whereas no enhancement was observable during VOR. This result indicates similarities between slow-phase OKN and SPEM, which are distinct from VOR.

Visual Tracking Neurons in Primate Area MST Are Activated by Smooth-Pursuit Eye Movements of an “Imaginary” Target

2003 ◽  
Vol 90 (3) ◽  
pp. 1489-1502 ◽  
Author(s):  
Uwe J. Ilg ◽  
Peter Thier
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Eye Movement ◽  
Visual Tracking ◽  
Smooth Pursuit ◽  
Rhesus Monkeys ◽  
Image Motion ◽  
Eye Position ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements

Because smooth-pursuit eye movements (SPEM) can be executed only in the presence of a moving target, it has been difficult to attribute the neuronal activity observed during the execution of these eye movements to either sensory processing or to motor preparation or execution. Previously, we showed that rhesus monkeys can be trained to perform SPEM directed toward an “imaginary” target defined by visual cues confined to the periphery of the visual field. The pursuit of an “imaginary” target provides the opportunity to elicit SPEM without stimulating visual receptive fields confined to the center of the visual field. Here, we report that a subset of neurons [85 “ imaginary” visual tracking (iVT)-neurons] in area MST of 3 rhesus monkeys were identically activated during pursuit of a conventional, foveal dot target and the “imaginary” target. Because iVT-neurons did not respond to the presentation of a moving “imaginary” target during fixation of a stationary dot, we are able to exclude that responses to pursuit of the “imaginary” target were artifacts of stimulation of the visual field periphery. Neurons recorded from the representation of the central parts of the visual field in neighboring area MT, usually vigorously discharging during pursuit of foveal targets, in no case responded to pursuit of the “imaginary” target. This dissociation between MT and MST neurons supports the view that pursuit responses of MT neurons are the result of target image motion, whereas those of iVT-neurons in area MST reflect an eye movement–related signal that is nonretinal in origin. iVT-neurons fell into two groups, depending on the properties of the eye movement–related signal. Whereas most of them (71%) encoded eye velocity, a minority showed responses determined by eye position, irrespective of whether eye position was changed by smooth pursuit or by saccades. Only the former group exhibited responses that led the eye movement, which is a prerequisite for a causal role in the generation of SPEM.

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