Voluntary Control of Smooth Eye Movements and their Velocity
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Smooth pursuit
Stimulus (psychology)
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Pursuit tracking eye movements were analyzed from selected patients with neurological injuries and compared to the responses of 20 normal subjects. The patients/subjects tracked a small spot of light moving sinusoidally in the horizontal plane at a frequency of 0.4 Hz and a peak-to-peak amplitude of 40 degrees. Eye-movement responses were separated into a smooth-pursuit component and a saccadic component. The smooth-pursuit component was analyzed by calculating the gain, phase, and asymmetry. The saccadic component was quantified by calculating the percentage of the total tracking movement contributed by the saccadic system. The patients with smooth-pursuit impairment exhibited a higher percentage of saccadic tracking and a lower smooth pursuit gain compared to the normal subjects. One patient with a unilateral lesion exhibited significant asymmetry in the smooth-pursuit component. In this case, the direction of the asymmetry indicated the side of the lesion.
Smooth pursuit
Saccadic eye movement
Electrooculography
Tracking (education)
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AbstractSmooth pursuit has been determined by the examiner's visualization as ‘smooth pursuit’, ‘saccadic pursuit’, or ‘ataxic pursuit’ according to the shapes of the eye movements on the ENG (electronystagmography) recording paper. Even since the introduction of computers for the measurement of smooth pursuit, however, no trial to compare quantitatively between smooth pursuit, saccadic pursuit and ataxic pursuit had been made up to the present. In the present work we analysed 10 smooth (normal) pursuits, 23 saccadic pursuits and 7 ataxic pursuits quantitatively with a microcomputer and found that the phase relationship between target movements and eye movements was the most prominent factor for distinguishing smooth pursuit pattern differences.Key Words: smooth pursuitquantitative analysisqualitative analysisphase lagprediction
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This paper describes a detailed study of horizontal eye movements associated with visual tracking of a smoothly moving target. Essentially all children, even at target velocities as low as 5°/sec., show some saccadic eye movements superimposed on smooth tracking movements. Detailed analysis of pursuit eye-movements from a group of 26 poor readers and 34 normal controls (8 to 13 yr.) showed that about 25% of poor readers have an abnormally raised saccadic component in smooth pursuit. This suggests that studies of eye movements during tracking of smoothly moving targets at low velocity, combined with a quantitative approach to data analysis, may be useful for early detection of a significant proportion of poor-reading children.
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Tracking (education)
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Summary Although animal research and some rare human case reports suggest that lesions of the dorsal pons yield saccadic and smooth pursuit eye movement deficits, little is known about the functional topology of the human pontine nuclei (PN) and whether limb movements are similarly affected as eye movements. Saccadic as well as SP eye and pointing movements were measured in six patients with lesions in the PN region. Five patients of the six exhibited dysmetric saccades, whilst smooth pursuit gain was reduced in four. Pontine lesions also alter the relationship between amplitude, velocity, and velocity skewness of saccadic eye movements. Limb movement trajectories were more curved in four patients. The results suggest that the lesions impair a general calibration mechanism that uses the parallel fiber-Purkinjecell synapse in the cerebellar cortex to adjust the timing of muscle innervation in visually guided oculomotor as well as limb movement tasks.
Smooth pursuit
Pons
Superior colliculus
Pontine nuclei
Supplementary eye field
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Horizontal smooth pursuit eye movements were quantitatively evaluated in forty patients with various neurological diseases (chronic alcoholism, acusticusneurinom and multiple sclerosis) as well as in twenty-four healthy subjects. Different frequency sinusoidal targets with an amplitude of 20 degrees were used. The quantitative analysis was possible after calculating the pursuit value as the difference between the saccadic part and the maximal amplitude of the recorded eye movement. Maximal and minimal P-values of 0.5, 0.7 and 0.9 Hz were chosen in the discriminant analyses. It is suggested that these parameters are very helpful in distinguishing between the groups of patients and the group of subjects.
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Saccadic eye movement
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Motor skills improve with age from childhood into adulthood, and this improvement is reflected in the performance of smooth pursuit eye movements. In contrast, the saccadic system becomes mature earlier than the smooth pursuit system. Therefore, the present study investigates whether the early mature saccadic system compensates for the lower pursuit performance during childhood. To answer this question, horizontal eye movements were recorded in 58 children (ages 5–16 yr) and 16 adults (ages 23–36 yr) in a task that required the combination of smooth pursuit and saccadic eye movements. Smooth pursuit performance improved with age. However, children had larger average position error during target tracking compared with adults, but they did not execute more saccades to compensate for their low pursuit performance despite the early maturity of their saccadic system. This absence of error correction suggests that children have a lower sensitivity to visual errors compared with adults. This reduced sensitivity might stem from poor internal models and longer processing time in young children.
Smooth pursuit
Tracking (education)
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Smooth pursuit
Component (thermodynamics)
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1. Voluntary eye movements were measured in the chronic, unanaesthetized monkey. A training technique is described which conditions the animals to follow a large variety of target trajectories. 2. The eye movements of the monkey are not qualitatively different from those of man. In response to random target motions the monkey also employs a combination of saccadic and smooth pursuit movements. 3. Monkeys execute their saccades more rapidly than humans. 4. Monkeys are capable of attaining smooth pursuit velocities which are twice as fast as those of man. 5. Most of the critical experiments showing the separate nature of the saccadic and smooth pursuit modes in man have been performed on monkeys with similar results. 6. Therefore, if one remains aware of the quantitative differences between the two primates, results of neurophysiological studies of the occulomotor system of the monkey can be expected to have considerable relevance when extrapolated to man.
Smooth pursuit
Neurophysiology
Saccadic eye movement
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• Using precise infrared recording instrumentation, we measured the eye-movement patterns in six schizophrenic patients who were taking medication and found saccadic intrusions and saccadic smooth-pursuit tracking in three. This defined some of the eye-movement irregularities reported previously by many investigators. A variety of eye-movement functions in addition to smooth pursuit exhibited these abnormalities, including fixation, vergence, and head-eye pursuit. Saccadic intrusions or saccadic pursuit also occurs in a number of neuro-ophthalmologic disorders, and occasionally In healthy normal subjects. Thus, these eye-movement abnormalities do not occur exclusively in schizophrenia.
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Saccadic eye movement
Electrooculography
Vergence (optics)
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Latencies of smooth pursuit and saccadic eye movement responses to a horizontal ramp target show considerable random variation from trial to trial, which is uncorrelated between the two types of response. This implies that the functional pathways that are responsible for most of the delay in each case are essentially independent.
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Uncorrelated
Saccadic eye movement
Variation (astronomy)
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