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PubMed2004

Non-Rapid Eye Movement Parasomnias.

Non-rapid eye movement parasomnias are unique physical or experiential phenomena that disrupt sleep. Non-rapid eye movement parasomnias are common in children, but they typically outgrow them. Sleep-stage shifts caused by sleep-disordered breathing and associated arousals may be precipitating events for episodes of parasomnia. Seizure disorders should always be considered in the differential diagnosis for the evaluation of parasomnias. Violent or injurious sleepwalking should be rapidly evaluated and treated.

Journal Article↗
PubMed1994

Eye movement desensitization across subjects: subjective and physiological measures of treatment efficacy.

Eye movement desensitization (EMD) was investigated in an experimental multiple baseline across subjects design. Six subjects who met the diagnostic criteria for Posttraumatic Stress Disorder (PTSD) were included in the study. While the EMD technique advanced by Shapiro has been reported to be clinically effective, major methodological issues have been raised which remain to be addressed. One issue raised is whether exposure to the traumatic image is sufficient to account for the reported clinical effects of EMD or whether the addition of saccadic eye movements is central to the treatment. This study attempted to address this concern by comparing two EMD-based procedures: a Non-saccade phase (without the saccadic eye movements) which functioned as a control and a second that included saccadic eye movements. Dependent variables included self-report information (SUDs, behavioral symptoms reports) and physiological data (heart rate and systolic blood pressure). The results showed no significant decreases in SUDs level with the EMD minus the saccadic eye movements procedure. However, five of the six subjects reported clinically significant decreases in their SUDs levels with the inclusion of the saccadic eye movements. This study appears to corroborate previous work employing single-case design as well as pre and postcomparisons.

Adult↗
PubMed1998

Visual representations during saccadic eye movements.

In normal vision, shifts of attention are usually followed by saccadic eye movements. Neurons in extrastriate area V4 are modulated by focal attention when eye movements are withheld, but they also respond in advance of visually guided saccadic eye movements. We have examined the visual selectivity of saccade-related responses of area V4 neurons in monkeys making delayed eye movements to receptive field stimuli of varying orientation. This task did not require the monkey to attend to orientation per se but merely to foveate the receptive field stimulus. We present evidence that the presaccadic enhancement exhibited by V4 neurons, quite separate from the response at stimulus onset, is a resurgent visual representation that seems as selective as the response is when the stimulus first appears. The presaccadic enhancement appears to provide a strengthening of a decaying featural representation immediately before an eye movement is directed to visual targets. We suggest that this reactivation provides a mechanism by which a clear perception of the saccade goal can be maintained during the execution of the saccade, perhaps for the purpose of establishing continuity across eye movements.

Animals↗
PubMed2006

Comparing eye movements recorded by search coil and infrared eye tracking.

OBJECTIVE: The performance of a new video-based infrared eye tracker (IR) was compared to the magnetic search coil technique (SC). Since the IR offers interesting possibilities as a diagnostic tool in neuro-ophthalmology, it was investigated whether the new device has overcome shortcomings that were reported from former IR systems. METHODS: Horizontal saccades were recorded using the IR and the SC. The IR allowed eye movement recordings at different sampling rates ranging from 250 Hz to 1000 Hz while the SC recorded at 1000 Hz. RESULTS/CONCLUSIONS: The results show that the IR and the SC were in good agreement and produced similar results. In contrast to other studies, the influence of the sampling rate of the IR was small. The saccade main-sequences did not show significant differences. The latency times observed for both systems were mainly in the short-latency range.

Adult↗
PubMed1981

Specific oculomotor deficit after diazepam. I. Saccadic eye movements.

Changes in saccadic eye movements before and after up to 10 mg oral diazepam were measured electrooculographically in diazepam-naive humans. Diazepam produced dose-dependent increases in saccade duration and decreases in maximum saccade velocity over a 2--36 degrees range of saccade amplitudes. The magnitude of drug-induced changes in saccade performance was proportional to the size of saccadic movement after 10 mg diazepam. Accuracy of saccade, latency to onset of saccade, latency to time of maximum velocity of saccade, and interval between the end of the initial saccade and the start of any corrective saccade were unaffected by the drug. Diazepam-induced changes in saccades were compared to saccades seen in patients with olivopontocerebellar atrophy reported in the literature, and were contrasted with saccade changes caused by opiates as reported previously. The possible participation of cerebellum in changes in saccadic function after diazepam was discussed.

Adult↗
PubMed2005

The effect of word predictability on the eye movements of Chinese readers.

Eye movements of Chinese readers were monitored as they read sentences containing target words whose predictability from the preceding context was high, medium, or low. Readers fixated for less time on high- and medium-predictable target words than on low-predictable target words. They were also more likely to fixate on low-predictable target words than on high- or medium-predictable target words. The results were highly similar to those of a study by Rayner and Well (1996) with English readers and demonstrate that Chinese readers, like readers of English, exploit target word predictability during reading.

Asian People↗
PubMed1983

Effects of an optokinetic background on pursuit eye movements.

The effects of an optokinetic background on pursuit eye movements was studied in four normal human subjects and seven patients with impaired pursuit and/or optokinetic nystagmus (OKN). Eye movements were recorded by DC electro-oculography and eye movement velocity was analyzed by a digital, microprocessor system. Tracking of a small laser target was performed against a featureless, white screen, a stationary OKN background that filled the entire visual field and an OKN background moving at constant velocity. The OKN background significantly affected pursuit in all subjects. The stationary background or background moving in the direction opposite to that of the laser target impaired pursuit; whereas, the background moving in the same direction as that of the target improved pursuit. The effects of the background on pursuit were greater in subjects with lower pursuit gains during tracking against the screen. An algebraic summation of independently induced pursuit and OKN eye movements could not account for all of the experimental observations.

Eye Movements↗
PubMed2006

The effect of word and character frequency on the eye movements of Chinese readers.

Eye movements of native Chinese readers were monitored as they read sentences containing target words that varied in terms of word frequency and character frequency. There was an effect of word frequency on fixation times on a target word and it was comparable in size to that typically found with readers of English. Furthermore, character frequency also influenced fixation time on the target word. The effect of the initial character in two character words was more pronounced than that of the second character. However, word frequency modulated the effect of character frequency. The effect of character frequency was attenuated with high frequency target words while it was quite apparent with low frequency target words.

Asian People↗
PubMedDate not supplied

Age-dependent changes in visually guided saccadic eye movements.

Voluntary horizontal saccadic eye movements (SEM) were recorded in 148 drug free healthy subjects (15-75 years of age). None had history and/or objective evidences of CNS abnormalities. SEM recordings took place always at the same time of the day, after a standard lunch. Peak saccadic velocity (PSV), saccade latency (SL) and saccade accuracy (SA) were extracted for each saccade session. A negative linear correlation was found between SEM parameters (PSV, SA, SL) and age. Aged subjects showed a significant (p less than 0.01) elongation of the to locate the target, a significant (p less than 0.01) decrease in PSV and a significant (p less than 0.01) decrement in SA.

Adolescent↗
PubMed1987

Effects of occipital lobectomy upon eye movements in primate.

1. Eye movements were recorded before and after bilateral occipital lobectomy in six rhesus monkeys trained to fixate and to follow small targets. Striate cortex was completely removed in two animals; small islands islands remained in the others. In all animals portions of extrastriate cortex were also removed but the medial superior temporal area in the superior temporal sulcus was largely spared. Optokinetic nystagmus (OKN) was markedly altered but not abolished in all animals. The immediate pursuit component of OKN was eliminated leading to a poor response to stimuli comprised of high frequencies. The velocity-storage component of OKN was present, but the maximum value of OKN that could be achieved was decreased to 6 and 16 degrees/s in the two most severely affected animals (preop, 65-116 degrees/s). The residual OKN was similar to that of afoveate animals with a diminished response to high velocities of retinal-image motion and a temporal to nasal predominance during monocular viewing. 2. In the initial postoperative period all animals appeared completely blind. Within 1-6 mo, however, they regained an ability to make visually guided saccades to, and smooth pursuit of, small targets. Saccades were nearly as accurate as preoperatively, but saccade amplitudes were more variable and saccade latencies increased. In the two animals with a complete removal of striate cortex, gains (eye velocity/target velocity) of smooth pursuit during sinusoidal tracking (60 degrees/s, 0.5 Hz) were 0.9 and 0.95. During tracking of step-ramp (Rashbass) stimuli with 60 degrees/s ramps, the average acceleration of the eyes during the first 120 ms of smooth pursuit was 189-278 degrees.s-1.s-1 (preop range, 154-418 degrees.s-1.s-1). In other respects, though, smooth pursuit was not normal. Latencies were increased two- to threefold, and tracking was more variable. 3. Paradoxically, as visually guided saccades and pursuit recovered, some other ocular motor functions deteriorated. Spontaneous and gaze-evoked nystagmus developed 3-6 mo after occipital lobectomy; the time constant of the neural eye-position integrator dropped to values as low as 2.6-4.8 s. The maximum slow-phase velocity of OKN also decreased. 4. The findings immediately after occipital lobectomy indicate that in normal primates occipital cortex is necessary for visually guided saccades and smooth pursuit as well as for the immediate component of OKN. Occipital cortex also makes the predominant contribution toward the generation of the velocity-storage component of OKN.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Enhancement of the vestibulo-ocular reflex by prior eye movements.

We investigated the effect of visually mediated eye movements made before velocity-step horizontal head rotations in eleven normal human subjects. When subjects viewed a stationary target before and during head rotation, gaze velocity was initially perturbed by approximately 20% of head velocity; gaze velocity subsequently declined to zero within approximately 300 ms of the stimulus onset. We used a curve-fitting procedure to estimate the dynamic course of the gain throughout the compensatory response to head rotation. This analysis indicated that the median initial gain of compensatory eye movements (mainly because of the vestibulo-ocular reflex, VOR) was 0. 8 and subsequently increased to 1.0 after a median interval of 320 ms. When subjects attempted to fixate the remembered location of the target in darkness, the initial perturbation of gaze was similar to during fixation of a visible target (median initial VOR gain 0.8); however, the period during which the gain increased toward 1.0 was >10 times longer than that during visual fixation. When subjects performed horizontal smooth-pursuit eye movements that ended (i.e., 0 gaze velocity) just before the head rotation, the gaze velocity perturbation at the onset of head rotation was absent or small. The initial gain of the VOR had been significantly increased by the prior pursuit movements for all subjects (P < 0.05; mean increase of 11%). In four subjects, we determined that horizontal saccades and smooth tracking of a head-fixed target (VOR cancellation with eye stationary in the orbit) also increased the initial VOR gain (by a mean of 13%) during subsequent head rotations. However, after vertical saccades or smooth pursuit, the initial gaze perturbation caused by a horizontal head rotation was similar to that which occurred after fixation of a stationary target. We conclude that the initial gain of the VOR during a sudden horizontal head rotation is increased by prior horizontal, but not vertical, visually mediated gaze shifts. We postulate that this "priming" effect of a prior gaze shift on the gain of the VOR occurs at the level of the velocity inputs to the neural integrator subserving horizontal eye movements, where gaze-shifting commands and vestibular signals converge.

Adult↗
PubMed1980

Specific oculomotor deficit after acute methadone. I. Saccadic eye movements.

Changes in saccadic eye movements before and after up to 10 mg oral methadone were measured electrooculographically in nontolerant nondependent humans. Undershoot of initial saccades increased with increasing size of horizontal target displacement (to 36 degrees) from a central viewing position. Dosage as low as 5 mg caused significant increase in saccade undershoot especially to target displacements greater than 10-15 degrees. Latency from target displacement to onset of initial saccade also increased after methadone. These results, in combination with the lack of significant drug effect on latency between initial saccade and corrective saccade, and on initial saccade duration, maximum velocity, and time to maximum velocity indicate methadone action on specific sensory, rather than motor, components of saccadic response. The similarity of alteration of saccadic response after methadone and after lesion of the upper layers of the superior colliculus in primates, as reported in the literature, suggests that opiate binding sites in the upper layers of the superior colliculus may be physiologically active.

Adult↗
PubMed1991

Exploring the third dimension with eye movements: better than stereopsis.

Eye movements are usually presumed to be irrelevant for (or detrimental to) stereoacuity. When targets of interest are not adjacent, however, better discrimination of distance can be achieved by looking back and forth between them. In order to exclude ordinary stereopsis and examine this viewing strategy in isolation, judgements of apparent equidistance have been obtained for pairs of small targets separated horizontally by the angular spacing that corresponds to the fovea-to-blind-spot distance. Precise, stereopsis-like evaluations of relative distance can be made by fixating each of those targets in turn, even if they are not simultaneously presented but are instead shown in alternation. Sequential comparisons of stimuli are thus involved in this form of distance discrimination, but direct utilization of oculomotor information (vergence) is rendered unlikely because very brief target presentation is sufficient. Hence, the evidence argues for "sequential stereopsis": comparisons of the disparities of targets, both seen foveally, before and after saccades. This interpretation makes stringent demands on oculomotor coordination during saccades, but measurements of vergence "noise" indicate that this requirement can probably be fulfilled.

Adolescent↗
PubMed2001

Time course of frequency effects in spoken-word recognition: evidence from eye movements.

In two experiments, eye movements were monitored as participants followed spoken instructions to click on and move pictures with a computer mouse. In Experiment 1, a referent picture (e.g., the picture of a bench) was presented along with three pictures, two of which had names that shared the same initial phonemes as the name of the referent (e.g., bed and bell). Participants were more likely to fixate the picture with the higher frequency name (bed) than the picture with the lower frequency name (bell). In Experiment 2, referent pictures were presented with three unrelated distractors. Fixation latencies to referents with high-frequency names were shorter than those to referents with low-frequency names. The proportion of fixations to the referents and distractors were analyzed in 33-ms time slices to provide fine-grained information about the time course of frequency effects. These analyses established that frequency affects the earliest moments of lexical access and rule out a late-acting, decision-bias locus for frequency. Simulations using models in which frequency operates on resting-activation levels, on connection strengths, and as a postactivation decision bias provided further constraints on the locus of frequency effects.

Eye Movements↗
PubMed1996

Object-based neglect: an investigation of the contributions of eye movements and perceptual completion.

Eye movements made by a patient with object-based neglect and no hemianopia, R.R., were recorded while he viewed whole, half, and chimaeric objects. When whole or chimaeric objects were presented centred on his initial fixation point, and when right half objects were presented, R.R. restricted his saccades to the right sides of the images. R.R.'s verbal identifications were consistent with these scan paths, since he correctly reported the identities of whole objects, right half objects, and the right sides of chimaeric objects, but failed to report objects on the left sides of chimaerics. When a left half object was presented to the left of initial fixation, however, R.R. made left saccades to scan the image and correctly named these objects; hence his failure to scan the left sides of chimaeric object cannot simply be attributed to an inability to make contralesional saccades. We examined the possibility of perceptual completion by testing R.R. with sets of whole and half shapes presented tachistoscopically and asking him to report what he had seen. When R.R. viewed whole shapes he correctly reported seeing a whole shape on every trial. However, R.R. often reported seeing right half objects as whole, whereas he was much less prone to report left half objects as perceptually whole. We discuss the nature of this perceptual completion, and conclude that both scan paths and completion are consequences of object-based neglect, not its causes.

Cerebrovascular Disorders↗
PubMed1989

Stereo and eye movement.

We describe a method to solve stereo correspondence using controlled eye (or camera) movements. Eye movements supply additional image frames and monocular depth estimate, which can be used to constrain stereo matching. Because the eye movements are small, traditional stereo techniques of stereo with multiple frame will not work. We develop an alternative approach using a systematic analysis to define a probability distribution for the errors. Our matching strategy then matches the most probable points first, thereby reducing the ambiguity for the remaining matches. We demonstrate this algorithms with several examples.

Computer Simulation↗
PubMed1982

Development and plasticity of visual and vestibular generated eye movements.

Slow phase horizontal eye movements, elicited by the vestibulo-ocular reflex (VOR) and/or visual pursuit (VP) systems, were examined in normal children (NC, 9-16 years) and normal adults (NA). At slow frequencies of sinusoidal stimulation of the body (with the head immobilized) and/or of a visual target, the NC (9-12 years) exhibited (a) immature VP and VOR Suppression and mature VOR Enhancement in the presence of a visual image; (b) immature VOR Suppression and mature VOR Enhancement in the presence of a non-visual image of the spatial location of a visual target, an extra-retinal signal; (c) inability to augment or depress the VOR gain with a non-visual image; (d) mature VOR Suppression ratios; and (e) adjustment of VOR gain to a high value. The maturational process was featured by (a) parallel development of VP and VOR Suppression; (b) modification of the VOR gain; and (c) an increasing ability to augment or depress the VOR with a non-visual image. The observations in NC (9-12) are ascribed to a maturational lag of an extra-retinal process interacting with mature retinal and vestibular processes and, hence, suggest that both the retinal and vestibular contributions to ocular stability predate the development of an extra-retinal signal. When mature, the central nervous system utilizes both extra-retinal and retinal signals to mediate adaptive regulation of VOR gain and to preserve stable visual pursuit motion and VOR Suppression. Our findings also suggest that during tasks requiring visual-vestibular interaction, VP and VOR mechanisms appear to be indirectly rather than directly coupled.

Adolescent↗
PubMed1989

Rapid eye movement generation in the primate. Physiology, pathophysiology, and clinical implications.

The trajectories of rapid eye movements are usually described in a Cartesian coordinate frame with a horizontal, vertical and torsional component. The sensory to motor coordinate transformations for horizontal components of rapid eye movements can be localized to neurons of the paramedian pontine reticular formation (PPRF), where long-lead and short-lead burst neurons are found. The equivalent area for recoding of vertical and torsional movement components is situated in the rostral interstitial nucleus of the MLF (rostral iMLF). Pause cells in caudal midline structures of the PPRF help to coordinate the various movement components. Experimental inactivation of these different neuron population lead to palsies of rapid eye movement generation. A unilateral PPRF lesion leads to a loss of all horizontal rapid eye movements towards the ipsilateral side. A bilateral PPRF lesion involving caudal midline structures leads to a bilateral horizontal gaze palsy in addition to a severe disruption of vertical and torsional eye movements. A bilateral rostral iMLF lesion leads to a loss of all rapid eye movements with a vertical or torsional movement component. A unilateral iMLF lesion leads to a loss of all rapid eye movements with an ipsilateral torsional component.

Animals↗