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At least 1,063 records · Page 59Linked to original sources
PubMed1996

A simplified calibration method for three-dimensional eye movement recordings using search-coils.

An algorithm is presented which allows the calibration of three-dimensional eye movements in two magnetic fields with two search-coils in one eye, whose relative orientation does not have to be known. Prior to recordings a calibration cube is placed in front of the eye to measure real and apparent crosstalk, produced by imprecisely oriented horizontal or vertical magnetic fields, and to obtain a first approximation of offset voltages. For calibration it suffices if one point is fixated and, in addition, spontaneous eye movements for 30-60 sec are performed. Additional fixation points can be used to improve the calibration. Position quaternions are applied for computing eye movement recordings from man and monkey and to determine Listing's plane.

Algorithms↗
PubMed2001

Sensorimotor integration compensates for visual localization errors during smooth pursuit eye movements.

To localize a seen object, the CNS has to integrate the object's retinal location with the direction of gaze. Here we investigate this process by examining the localization of static objects during smooth pursuit eye movements. The normally experienced stability of the visual world during smooth pursuit suggests that the CNS essentially compensates for the eye movement when judging target locations. However, certain systematic localization errors are made, and we use these to study the process of sensorimotor integration. During an eye movement, a static object's image moves across the retina. Objects that produce retinal slip are known to be mislocalized: objects moving toward the fovea are seen too far on in their trajectory, whereas errors are much smaller for objects moving away from the fovea. These effects are usually studied by localizing the moving object relative to a briefly flashed one during fixation: moving objects are then mislocalized, but flashes are not. In our first experiment, we found that a similar differential mislocalization occurs for static objects relative to flashes during pursuit. This effect is not specific for horizontal pursuit but was also found in other directions. In a second experiment, we examined how this effect generalizes to positions outside the line of eye movement. We found that large localization errors were found in the entire hemifield ahead of the pursuit target and were predominantly aligned with the direction of eye movement. In a third experiment, we determined whether it is the flash or the static object that is mislocalized ahead of the pursuit target. In contrast to fixation conditions, we found that during pursuit it is the flash, not the static object, which is mislocalized. In a fourth experiment, we used egocentric localization to confirm this result. Our results suggest that the CNS compensates for the retinal localization errors to maintain position constancy for static objects during pursuit. This compensation is achieved in the process of sensorimotor integration of retinal and gaze signals: different retinal areas are integrated with different gaze signals to guarantee the stability of the visual world.

Brain↗
PubMed2006

Effects of bilateral eye movements on gist based false recognition in the DRM paradigm.

The effects of saccadic bilateral (horizontal) eye movements on gist based false recognition was investigated. Following exposure to lists of words related to a critical but non-studied word participants were asked to engage in 30s of bilateral vs. vertical vs. no eye movements. Subsequent testing of recognition memory revealed that those who undertook bilateral eye movement were more likely to correctly recognise previously presented words and less likely to falsely recognise critical non-studied associates. This result joins other research in demonstrating the conditions in which false memory effects can be attenuated.

Adult↗
PubMed1992

Eye movement tics.

An 8-year-old girl presented with opsoclonus-like eye movement and an 18 month history of intermittent facial tics. Investigations were all normal. Electro-oculography showed the eye movements to be of variable amplitude (10-40 degrees), with no intersaccadic interval, and with a frequency of 3-4 Hz. Saccades, smooth pursuit, optokinetic, and vestibular reflexes were all normal. These abnormal eye movements eventually disappeared. It is thought that they were a form of ocular tics.

Child↗
PubMed2001

Optimizing visual motion perception during eye movements.

We usually perceive a stationary, stable world and we are able to correctly estimate the direction of heading from optic flow despite coherent visual motion induced by eye movements. This astonishing example of perceptual invariance results from a comparison of visual information with internal reference signals predicting the visual consequences of an eye movement. Here we demonstrate that the reference signal predicting the consequences of smooth-pursuit eye movements is continuously calibrated on the basis of direction-selective interactions between the pursuit motor command and the rotational flow induced by the eye movement, thereby minimizing imperfections of the reference signal and guaranteeing an ecologically optimal interpretation of visual motion.

Chi-Square Distribution↗
PubMed2001

Overlap of saccadic and pursuit eye movement systems in the brain stem reticular formation.

Recent physiological studies have suggested that there are several sites of interaction between the neural pathways that control saccadic eye movements and those that control visual pursuit movements. To address the question of saccade/pursuit interaction from a neuroanatomical point of view, we have studied the connections from the smooth and saccadic eye movement subregions of the frontal eye field (FEFsem and FEFsac, respectively) to the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) in four Cebus apella monkeys. The riMLF has traditionally been considered to be a premotor center for vertical saccadic eye movements on the basis of single neuron recording experiments, microstimulation experiments, and surgical or chemical lesion experiments. We localized the functional subregions of the FEF with the use of low-threshold (< or =50 microA) intracortical microstimulation. Biotinylated dextran amine or lectin from triticum vulgaris (wheat germ), peroxidase labeled, was placed into these functionally defined subregions to label anterogradely the terminals of axons that originated in the FEF. Our results demonstrate that both the FEFsem and FEFsac send direct projections to the ipsilateral riMLF. The distribution and density of labeling from the FEFsem are comparable to those from the FEFsac. The direct FEFsem-to-riMLF projection suggests a possible role of the riMLF in smooth pursuit eye movements and supports the hypothesis that there is interaction between the saccadic and pursuit subsystems at the brain stem level.

Animals↗
PubMed1981

Variability and development of a normative data base for saccadic eye movements.

The duration, peak velocity, and acceleration of the saccadic eye movements of 13 normal subjects are plotted as functions of saccadic magnitude. The apparent peak velocity of a saccadic eye movement is sensitive to the algorithms used to calculate the velocity. The velocity channel filter should have zero phase shift and a cutoff frequency between 60 and 100 Hz in order to limit noise but pass all the signal information. Some subjects fatigue rapidly; their parameters fall outside the normal range of values.

Adult↗
PubMed1986

Investigation of the visual cytoscreening of conventional gynecologic smears. II. Analysis of eye movement.

The perception of visual information in cytoscreening was studied: eye movements were recorded while the cytotechnologist was screening cervical smears by means of a projection screen. Four phases of eye movement could be distinguished: small, aimless movements during the stage movement; a latency period with a duration of about 180 milliseconds; saccadic movement to the position of an object; and fixation on an object. These components explain the two-phase behavior of cytoscreening found in our previous investigations of the stage movement. Visual perception during the period of latency was found to be the most important since only those objects that are recognized by peripheral vision during this period can trigger the necessary saccadic movement before fixation takes place. The scanpath of search in the stationary field of view is determined by the conspicuousness of the objects; the main features of conspicuousness are size and contrast. Even with the comparatively small fields of view (24 degrees and 29 degrees in diameter) used in these experiments, it was found that the detection threshold of peripheral vision increases towards the margin of the field of view. This raises the question of whether the use of large-field binoculars (with 40-degree visual angles) may cause higher false-negative rates for samples with only a few atypical cells.

Cytodiagnosis↗
PubMed1990

Mapping of brainstem lesions by the combined use of tests of visually-induced eye movements.

To determine the diagnostic value of visually-induced eye movements for indicating the lateralization of the lesion, optokinetic nystagmus (OKN), fixation-suppression of caloric nystagmus and pursuit eye movements were investigated in 28 patients who showed discrete unilateral brainstem lesions. In all patients, pursuit gains decreased in parallel with the direction of the impairment of slow-phase OKN velocity with a significant left/right difference. Decreases of gains were predominantly towards the affected side in 22 patients, whereas they were predominantly towards the contralateral side in 2 patients with dorsal tegmental pontine lesions and in 4 out of 8 patients with Wallenberg's syndrome. The relationship of pursuit gains to percentage reduction of fixation-suppression of caloric nystagmus (%FS) showed no correlation. The following four groups were classified. In group A, which was the largest, pursuit gains and %FS decreased predominantly towards the lesioned side. This group consisted of 5 patients with lesions in the midbrain, 6 patients with lesions in the ventral pons and 4 out of 8 patients with Wallenberg's syndrome. The opposite of group A was group D, showing reverse electro-oculographic (EOG) patterns to those in group A in relation to the lesioned side. Group D consisted of 2 patients with lesions in the dorsal pontine tegmentum. This observation, taken together with the decreases of pursuit and OKN gains in relation to the lesioned side, might indicate that lesions of ascending fibres are responsible for pursuit and OKN abnormalities. Group B, consisting of 7 patients with lesions either in the superior or middle cerebellar peduncles, showed decreased pursuit gains predominantly towards the lesioned side and %FS reduced predominantly towards the side contralateral to the lesion. EOGs of these patients were consistent with the results of floccular ablation in the monkey. In group C, these two parameters showed patterns opposite to those in group B in relation to the lesioned side and this group consisted of the other 4 patients with Wallenberg's syndrome. In patients of this group, the inferior cerebellar peduncle might be involved. The combined use of these tests is thus useful for lateralizing the lesion in the brainstem.

Brain Diseases↗
PubMed1991

Smooth pursuit and saccadic eye movements and neurological soft signs in obsessive-compulsive disorder.

Patients with obsessive-compulsive disorder (OCD) demonstrate an increased number of neurological soft signs as well as neuroanatomic abnormalities detected with modern imaging techniques. Quantitative analysis of eye movements has proved fruitful in investigations of other neuropsychiatric disorders with similar findings. Therefore, we studied the smooth pursuit and saccadic eye movements of 8 OCD patients and 12 normal controls using infrared oculography and computerized pattern recognition software. We also measured neurologic soft signs using a standardized rating instrument. Despite having an increased number of neurological soft signs, OCD patients' performance on a variety of measures of eye movement was not significantly impaired. Neither the severity of obsessions or compulsions nor the number of neurologic soft signs correlated with any of the parameters of eye movement function. We conclude that OCD patients do not have prominent oculomotor dysfunction and that eye movement dysfunction and neurologic soft signs are not inextricably linked.

Adult↗
PubMed1984

Functional representation of eye movements in the flocculus of monkeys (Macaca fuscata).

The flocculus of the monkey was mapped with microstimulation methods in chronic preparations. Three types of low threshold, disconjugate eye movements were elicited: (1) a lateral deviation of the ipsilateral eye, (2) a downward deviation of the ipsilateral eye and (3) counterclockwise rotation of the ipsilateral eye. Horizontal eye movements were obtained from folia 2, 3, 4 and 6-10 of the flocculus, and the region eliciting horizontal eye movements was traced in the sagittal plane over a distance of 4 mm in one animal. However, sites flanking these horizontal movement sites produced either vertical movements, rotatory movements or failed to produce a movement of either eye. These findings suggest a zonal organization of flocculus functions in monkeys that is consistent with the differential projections of flocculo-vestibular connections revealed by retrograde tracing studies [2].

Animals↗
PubMed2003

[Exploratory eye movement in children with ADHD].

OBJECTIVE: To explore the character of the exploratory eye movement in ADHD children. METHODS: The eye mark recorder (model IV) was used to record the eye movements in 33 ADHD children and 33 normal controls matched by age and sex, using t-test to compare the differences of the numbers of eye fixations, total eye scanning lengths, mean eye scanning lengths, cognitive search scores, responsive search scores and D values between the two groups. RESULTS: ADHD children showed significantly fewer frequent numbers of eye fixations and longer mean eye scanning lengths than the normal controls. The responsive search score of ADHD children was significantly lower than that of the control group. ADHD children had a positive D value and the normal controls had a negative D value. CONCLUSION: ADHD children had fewer frequent numbers of eye fixation, longer mean eye scanning length and lower responsive search score than the normal controls, which may be the evidence of executive dysfunctions.

Adolescent↗
PubMed2000

The presumed influence of attention on accuracy in the developmental eye movement (DEM) test.

BACKGROUND: The developmental eye movement (DEM) test is a clinical test used widely to evaluate ocular motility function (accuracy and speed) in school-age children. PURPOSE: The purpose of this study was to investigate, retrospectively, the change in accuracy over time while performing the DEM horizontal reading task in children. METHODS: The charts from children who had performed the DEM test during a routine eye examination in a pediatric optometry service were reviewed. The study included 22 patients (6 to 11 years old, 12 boys, 10 girls) who had a routine eye examination that was precepted by one of the authors (R.C.) during the period of 1995 to 1999. Patients were divided into two categories: 1) those with abnormal DEM test results and 2) a control group consisting of those with normal DEM test results. Chart review was done consecutively within each category. Collected data included patient age, gender, refractive error, and DEM test results. For analysis, the horizontal task of the DEM was divided into two halves (I and II), Part I always preceded part II, and data was sorted as the number of errors per part. RESULTS: More errors in accuracy occurred in part II than in part I (Wilcoxon signed rank test, p < or = 0.01) of the horizontal DEM test in the group of subjects with an abnormal DEM test. No differences in the number of errors in parts I and II of the horizontal task of the DEM were found in the control group. CONCLUSIONS: Findings showed that when excessive errors in accuracy occurred, the number of errors increased over time. If the errors were caused by an oculomotor dysfunction found in the DEM, errors should be equally distributed throughout the text. If errors were caused by fatigue, a difference in parts I and II should have occurred in both the test and the control group. These findings suggest that attention may influence accuracy over time in those patients that do poorly on the DEM test.

Aging↗
PubMed1982

Saccadic eye movements are coordinated with head movements in walking chickens.

1. Saccadic eye movements during walking were studied in chickens using cinematography. 2. Saccades were made during about 80% of the thrust phases of head bobbing, and not made in the hold phases. 3. The coordination of saccades with head movements maintains clear vision for the largest possible proportion of the time. 4. The absence of saccades in hold phases and in some thrusts is probably not the result of insufficient time to organize a saccade.

Animals↗
PubMed1995

Possible mechanism of rapid eye movement sleep deprivation induced increase in Na-K ATPase activity.

Rapid eye movement sleep deprivation increases Na-K ATPase activity and decreases aminergic neuronal firing rate as well as norepinephrine degrading enzyme, monoamine oxidase, activity. On the other hand, norepinephrine is known to increase Na-K ATPase activity. Hence, this study was conducted to find if the deprivation induced increase in Na-K ATPase activity is mediated by norepinephrine. Rapid eye movement sleep deprived rats were injected with either alpha-1 or beta adrenoceptor antagonist or alpha-2 adrenoceptor agonist and after 8 h the Na-K ATPase activity of the brain was estimated. In an attempt to simulate in vivo conditions, norepinephrine was added to an in vitro brain homogenate preparation in the presence or absence of alpha or beta adrenoceptor blockers and the enzyme activity was estimated. The results showed that the enzyme activity was decreased by alpha-1 antagonist as well as by alpha-2 agonist treatment in in vivo preparations. Norepinephrine increased enzyme activity in the in vitro preparation and the increase was prevented by the alpha-1 antagonist. The results of this study suggest that rapid eye movement sleep deprivation induced increase in Na-K ATPase activity may be mediated by norepinephrine acting on either alpha-1 and/or alpha-2 receptors.

Adrenergic Agonists↗
PubMed1994

Senescence of human visual-vestibular interactions: smooth pursuit, optokinetic, and vestibular control of eye movements with aging.

Natural aging entails progressive deterioration in a variety of biological systems. This study focuses on visual and vestibular influences on human eye movements as a function of aging. Eye movements were recorded (search-coil technique) during visual, vestibular, and combined stimuli in subjects across a broad range of ages (18-89 years). Two types of visual following were assessed: smooth pursuit (SP) of a small discrete target, and optokinetic (OKR) following of a large-field striped image. The vestibulo-ocular reflex (VOR) was studied during head rotation in darkness. Visual-vestibular interactions were recorded during rotation in two ways: when the optokinetic scene was earth-fixed, resulting in visual enhancement of the VOR (VVOR), and when the visual image was head-fixed, allowing visual suppression of the VOR (VSVOR). Stimuli consisted of horizontal sinusoidal oscillations over the frequency range 0.025-4 Hz. Trials were analyzed to yield response gain (peak horizontal eye/stimulus velocities) and phase (asynchrony, in degrees, between eye and stimulus velocity signals). VOR gain in young subjects was greatest (near 0.9) at 2.5-4 Hz but declined steadily with decreasing frequency, while phase hovered near zero until 0.1 Hz and then developed a progressively increasing lead. Effects of advancing age were small, given the modest head velocities presented, and were most noticeable as an increase in phase lead and decline in gain at the lowest frequencies (< or = 0.1 Hz). The two forms of visual following and all conditions of visual-vestibular interactions displayed more prominent age-dependent changes. OKR and SP response characteristics (0.25-4 Hz) closely resembled each other. Gain was greatest at 0.25 Hz, while phase was near 0 degree. As frequency increased, gain declined while phase lag rose. However, both gain and phase lag tended to be slightly greater for OKR than for SP responses. Both SP and OKR response properties deteriorated progressively with increasing age, as witnessed by a progressive decline in gain and increase in phase lag, even at modest frequencies (e.g., 0.25-1.0 Hz). VVOR responses were generally closer to the ideal of 1.0 in gain and 0 degree in phase than either the VOR or visual following alone. A subtle but significant age-dependent decline in VVOR performance occurred at the lowest frequencies. VSVOR response characteristics were close to those of the VOR and VVOR at 4 Hz, where visual influences on eye movements are generally inconsequential.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1988

Light transducer for the biological clock: a function for rapid eye movements.

To test the hypothesis that the rapid eye movements (REMs) of paradoxical sleep (PS) transmit information about environmental light: dark cycles, spontaneous locomotor patterns were studied in rats following surgical disconnection of the extraocular muscles and thus deprived only of the eye movement component of REM sleep. Entrainment of the circadian spontaneous activity cycle to the light: dark cycle was abolished after sectioning the extra-ocular muscles of rats, but not in sham-operated controls. Endogenous (free running) circadian patterns of spontaneous activity were preserved in the operated animals. The results are consistent with our electrophysiologic studies showing that REMs induce light modulated electrical potentials in brain regions that influence circadian rhythms of activity.

Animals↗
PubMed1986

Visual motion processing for the initiation of smooth-pursuit eye movements in humans.

We have used the initiation of pursuit eye movements as a tool to reveal properties of motion processing in the neural pathways that provide inputs to the human pursuit system. Horizontal and vertical eye position were recorded with a magnetic search coil in six normal adults. Stimuli were provided by individual trials of ramp target motion. Analysis was restricted to the first 100 ms of eye movement, which precedes the onset of corrective feedback. By recording the transient response to target motion at speeds the pursuit motor system can achieve, we investigated the visual properties of images that initiate pursuit. We have found effects of varying the retinal location, the direction, the velocity, the intensity, and the size of the stimulus. Eye acceleration in the first 100 ms of pursuit depended on both the direction of target motion and the initial position of the moving target. For horizontal target motion, eye acceleration was highest if the stimulus was close to the center of the visual field and moved toward the vertical meridian. For vertical target motion, eye acceleration was highest when the stimulus moved upward or downward within the lower visual field. The shape of the relationship between eye acceleration and initial target position was similar for target velocities ranging from 1.0 to 45 degrees/s. The initiation of pursuit showed two components that had different visual properties and were expressed early and late in the first 100 ms of pursuit. In the first 20 ms, instantaneous eye acceleration was in the direction of target motion but did not depend on other visual properties of the stimulus. At later times (e.g., 80-100 ms after pursuit initiation), instantaneous eye acceleration was strongly dependent on each property we tested. Targets that started close to and moved toward the position of fixation evoked the highest eye accelerations. For high-intensity targets, eye acceleration increased steadily as target velocity increased. For low-intensity targets, eye acceleration was selective for target velocities of 30-45 degrees/s. The properties of pursuit initiation in humans, including the differences between the early and late components, are remarkably similar to those reported by Lisberger and Westbrook (12) in monkeys. Our data provide evidence that the cell populations responsible for motion processing are similar in humans and monkeys and imply that the functional organization of the visual cortex is similar in the two species.

Adult↗