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At least 811 records · Page 45Linked to original sources
PubMed1979

Hans Gertz revisited: the different effects of invisibility and darkness on pursuit eye movements.

Subjects were required to track their self-moved hands with smooth eye movements in total darkness. The effect of holding transparent and opaque screens between the eyes and the hand upon pursuit eye movements was examined. Opaque screens produced a significant decrement in pursuit when the eye was moving in a direction in which it was generally less efficient at making smooth eye movements.

Darkness↗
PubMed2001

Adaptive changes in smooth pursuit eye movements induced by cross-axis pursuit-vestibular interaction training in monkeys.

The smooth pursuit system interacts with the vestibular system to maintain the accuracy of eye movements in space. To understand neural mechanisms of short-term modifications of the vestibulo-ocular reflex (VOR) induced by pursuit-vestibular interactions, we used a cross-axis procedure in trained monkeys. We showed earlier that pursuit training in the plane orthogonal to the rotation plane induces adaptive cross-axis VOR in complete darkness. To further study the properties of adaptive responses, we examined here the initial eye movements during tracking of a target while being rotated with a trapezoidal waveform (peak velocity 30 or 40 degrees/s). Subjects were head-stabilized Japanese monkeys that were rewarded for accurate pursuit. Whole body rotation was applied either in the yaw or pitch plane while presenting a target moving in-phase with the chair with the same trajectory but in the orthogonal plane. Eye movements induced by equivalent chair rotation with or without the target were examined before and after training. Before training, chair rotation alone resulted only in the collinear VOR, and smooth eye movement-tracking of orthogonal target motion during rotation had a normal smooth pursuit latency (ca 100 ms). With training, the latency of orthogonal smooth tracking eye movements shortened, and the mean latency after 1 h of training was 42 ms with a mean gain, at 100 ms after stimulus onset, of 0.4. The cross-axis VOR induced by chair rotation in complete darkness had identical latencies with the orthogonal smooth tracking eye movements, but its gains were <0.2. After cross-axis pursuit training, target movement alone without chair rotation induced smooth pursuit eye movements with latencies ca 100 ms. Pursuit training alone for 1 h using the same trajectory but without chair rotation did not result in any clear change in pursuit latency (ca 100 ms) or initial eye velocity. When a new target velocity was presented during identical chair rotation after training, eye velocity was correspondingly modulated by just 80 ms after rotation onset, which was shorter than the expected latency of pursuit (ca 100 ms). These results indicate that adaptive changes were induced in the smooth pursuit system by pursuit-vestibular interaction training. We suggest that this training facilitates the response of pursuit-related neurons in the cortical smooth pursuit pathways to vestibular inputs in the orthogonal plane, thus enabling smooth eye movements to be executed with shorter latencies and larger eye velocities than in normal smooth pursuit driven only by visual feedback.

Adaptation, Physiological↗
PubMed1992

Exploratory eye movements in schizophrenic patients and patients with frontal lobe lesions.

Exploratory eye movements in 20 schizophrenics, 18 patients with frontal lobe lesions (9 right-sided and 9 left-sided) and 20 normal controls were examined with an eye mark recorder while they viewed stationary S-shaped figures. The eye movements made during the subject's first 15-s viewing of an original figure were analyzed. Patients with right frontal lobe lesions (RF) and schizophrenics (S) had lower scores than normal controls (NC) for the number of eye fixations, total eye scanning length and mean eye scanning length. Each subject was then shown two other figures slightly different from the original and was requested to compare them with the original. After comparing them, the subject was asked the question, "Are there any other differences?" The eye movements made over the ensuing 5 s in response to this question were scored using the responsive search score (RSS). The RSS was low only in the S group. The subject was also asked to reproduce the original figure before and after making comparisons between the figures. The RF and S groups were poorer at reproduction than the NC group. These findings suggest that there is disordered function of the right frontal lobe in schizophrenia, and that schizophrenia is due not only to localized damage to one part of the brain but to more widespread damage.

Adult↗
PubMed2004

Latency of adaptive vergence eye movements induced by vergence-vestibular interaction training in monkeys.

Clear vision of objects that move in depth toward or away from an observer requires vergence eye movements. The vergence system must interact with the vestibular system to maintain the object images on the foveae of both eyes during head movement. Previous studies have shown that training with sinusoidal vergence-vestibular interaction improves the frequency response of vergence eye movements during pitch rotation: vergence eye velocity gains increase and phase-lags decrease. To further understand the changes in eye movement responses in this adaptation, we examined latencies of vergence eye movements before and after vergence-vestibular training. Two head-stabilized Japanese monkeys were rewarded for tracking a target spot moving in depth that required vergence eye movements of 10 degrees/s. This target motion was synchronized with pitch rotation at 20 degrees/s. Both target and chair moved in a trapezoidal waveform interspersed with random inter-trial intervals. Before training, pitch rotation in complete darkness without a target did not induce vergence eye movements. Mean latencies of convergence and divergence eye movements induced by vergence target motion alone were 182 and 169 ms, respectively. After training, mean latencies of convergence and divergence eye movements to a target synchronized with pitch rotation shortened to 65 and 53 ms, and vergence eye velocity gains (relative to vergence target velocity) at the normal latencies were 0.68 and 1.53, respectively. Pitch rotation alone without a target induced vergence eye movements with similar latencies after training. These results indicate that vestibular information can be used effectively to initiate vergence eye movements following vergence-vestibular training.

Adaptation, Physiological↗
PubMed2002

Characteristics of eye movement and cognition during simulated landing of aircraft.

Objective. To examine how the subject scans different parts of display panels and how the attention is distributed through the analysis of the eye movement principle and the cognition of the brain. Method. An experiment was conducted to simulate the airplane's landing course and eye movement data were recorded with eye movement measure system (EMMS). Result. There were three regions of interest (ROI) on which the subject's attention was concentrated. The subject's visual activity was active in the three ROIS and attention's shifting and distribution was between ROIS. Conclusion. Eye movement were driven by the top-down processing and the distribution of the attention. The consequence of the eye movement makes the subject maintain a continuous situation awareness.

Aircraft↗
PubMed2002

Eye movements of large populations: I. Implementation and performance of an autonomous public eye tracker.

This paper details the design and construction of an autonomous public eye tracker exhibit, which was installed at the National Gallery, London, in 2000/2001. For over 3 months, it functioned both as an informative exhibit and as a controlled eye movement experiment, gathering data from over 5,000 participants. The issues associated with automatic unattended recording of the eye movements of members of the public are discussed. The performance of the exhibit is examined, and its successes and problem areas are highlighted with regard to potential applications and future exhibits. The success of the project proves the viability of autonomous public eye trackers as both data-gatherers and public exhibits.

Adolescent↗
PubMed1989

Presaccadic spike potentials with large horizontal eye movements.

Presaccadic spike potentials were recorded from electrodes at the inner canthus and below the eye in 10 normal subjects for a range of horizontal saccades (5 degrees, 10 degrees, 20 degrees and 40 degrees). An eye movement trace was recorded for 20 abducting and 20 adducting saccades to determine the beginning of the saccade, and the spike potential back-averaged from this point. The latencies of the spike potential onset and peak were found with respect to the start of the eye movement and the amplitude from the onset to the peak was measured for each saccade size. The latency values remained constant throughout the range of eye movement sizes, although adducting saccades showed an earlier onset and peak latency than abducting saccades. The amplitude data, however, showed a definite relationship between saccade size and spike potential amplitude, with a significant increase in the amplitude for saccades between 10 degrees and 40 degrees (inner electrode abduction, lower electrode abduction and adduction P less than 0.01; inner electrode adduction P less than 0.05). A possible explanation of this increase in amplitude is hypothesised from a computer model of the action potential activity that may occur in the extraocular muscles before an eye movement.

Action Potentials↗
PubMed1982

Graves' ophthalmopathy evaluated by infrared eye-movement recordings.

Thirteen patients with varying degrees of Graves' ophthalmopathy were examined using high-resolution infrared oculography to determine peak velocities for horizontal eye movements between 3 degrees and 30 degrees. As severity of the orbital disease increased, peak velocities became substantially lower. Vertical-muscle surgery failed to have any effect on peak velocity of horizontal eye movements. In contrast, orbital decompression caused notable improvement in peak velocity of eye movements. Eye-movement recordings, which provide a measure of extraocular muscle function rather than structure, may provide a safe, sensitive, and accurate method for classifying and following up patients with Graves' ophthalmopathy.

Adult↗
PubMed1992

Effects of diazepam and D-amphetamine on rhythmic pattern of eye movements in goldfish.

The effects of diazepam and D-amphetamine on spontaneous, vestibular- and visually-induced eye movements were studied in the restrained goldfish. These animals showed a stereotyped pattern of spontaneous eye movements that scanned the visual field in the horizontal plane. Fourier analysis of these eye movements revealed a rhythmic pattern of about 5 cycles per minute, whose frequency increased to double and decreased to half following treatment with diazepam and D-amphetamine, respectively. However, the fast and slow components of vestibulo-ocular and optokinetic reflexes, as well as peculiar blink-like movements, remained unchanged at the same drug doses. These results suggest the presence of a central pattern generator for spontaneous eye movements in the goldfish, whose oscillation frequency is pharmacologically modifiable.

Animals↗
PubMed2006

[A case of normal-tension glaucoma with impaired eye movements in a young patient].

BACKGROUND: We report a case of normal-tension glaucoma(NTG) with impaired eye movements in a young patient. CASE: A 22-year-old man with enlarged optic disc cuppings and visual field defects was suspected to have NTG, and was found, upon examination, to have impaired eye movements. Intraocular pressure recordings, including diurnal variation, were under 21 mmHg. Gonioscopic findings were normal. Magnetic resonance image(MRI) showed no particular findings. The patient was diagnosed with NTG. Using the 123I-iodoamphetamine single photon emission computed tomography (123I-IMP SPECT), decreased cerebral blood flow was detected in the patient's occipital lobe and an electro-oculogram showed impaired eye movements during smooth pursuit. The patient's visual field defects have increased over the last two years, but, no accompanying change in his eye movements has been observed. CONCLUSION: The patient in this case has NTG with impaired eye movements and decreased cerebral blood flow suggesting that some disorder of the central nervous system may be one of the causative mechanisms of NTG.

Adult↗
PubMed1996

Craniotopic defects of smooth pursuit and saccadic eye movement.

I recorded smooth pursuit and saccadic eye movements in six patients with unilateral cerebral infarction. By comparing responses within the hemiranges of eye position to the right and left of the orbital midline and in rightward and leftward directions, I quantified craniotopic and directional ocular motor deficits. Two patients had ipsiversive gaze deviation and severe craniotopic defects in which they could not generate smooth pursuit or saccadic eye movement into the contralateral orbital hemirange. Three patients without gaze deviation generated worse smooth pursuit in the contralateral hemirange than in the ipsilateral hemirange, but each had symmetric saccades according to eye position. All patients with craniotopic pursuit defects also had directional smooth tracking asymmetries in which eye velocities were lower for targets moving ipsilaterally than for targets moving contralaterally. Craniotopic and directional defects were associated with damage in the frontal eye field region. Orbital position is taken into account by cerebral circuits that govern smooth pursuit and saccades.

Adult↗
PubMed2005

FMRI of response to nicotine during a smooth pursuit eye movement task in schizophrenia.

OBJECTIVE: Nicotine temporarily normalizes smooth pursuit eye movement deficits in schizophrenia. This study used functional magnetic resonance imaging (fMRI) to examine changes in brain hemodynamic response associated with nicotine administration during a smooth pursuit eye movement task in subjects with schizophrenia. METHOD: Nine subjects with schizophrenia performed the eye movement task while undergoing fMRI. Subjects then were given nicotine or placebo and repeated the task while being scanned. Subjects repeated the procedure the following week, receiving the counterbalanced condition. RESULTS: Compared with placebo, nicotine was associated with greater activity in the anterior and posterior cingulate gyri, precuneus, and area MT/MST and less activity in the hippocampus and parietal eye fields. CONCLUSIONS: Changes in area MT/MST and the cingulate gyrus are consistent with an improvement in perception and attention to moving stimuli. The most important observed difference between nicotine and placebo--less activation of the hippocampus after nicotine than after placebo administration--is consistent with nicotinic receptor mediation of inhibitory neuronal dysfunction in schizophrenia.

Adult↗
PubMed2006

Distractor interference during smooth pursuit eye movements.

When 2 targets for pursuit eye movements move in different directions, the eye velocity follows the vector average (S. G. Lisberger & V. P. Ferrera, 1997). The present study investigates the mechanisms of target selection when observers are instructed to follow a predefined horizontal target and to ignore a moving distractor stimulus. Results show that at 140 ms after distractor onset, horizontal eye velocity is decreased by about 25%. Vertical eye velocity increases or decreases by 1 degrees /s in the direction opposite from the distractor. This deviation varies in size with distractor direction, velocity, and contrast. The effect was present during the initiation and steady-state tracking phase of pursuit but only when the observer had prior information about target motion. Neither vector averaging nor winner-take-all models could predict the response to a moving to-be-ignored distractor during steady-state tracking of a predefined target. The contributions of perceptual mislocalization and spatial attention to the vertical deviation in pursuit are discussed.

Adult↗
PubMed1996

Short-latency compensatory eye movements associated with a brief period of free fall.

The vertical eye movements induced by a brief period of free fall were recorded from three monkeys (Macaca mulatta) using the electromagnetic search coil technique. Free fall was initiated in total darkness immediately following binocular fixation of one of six target lights located at viewing distances ranging from 20 to 107 cm. Responses consisted of an initial transient downward eye movement (anticompensatory direction) with a latency of a few milliseconds at most followed by a sustained upward (compensatory) eye movement. The early transient was independent of viewing distance and attributed to an artifact, whereas the later component was a linear function of the inverse of the prior viewing distance and attributed to the translational vestibulo-ocular reflex (TVOR). Response latencies for the four nearer viewing distances were determined from the individual eye velocity traces using a computerized algorithm: after removing the initial transient by subtracting the mean response obtained with the most distant viewing, a regression line was fitted to the initial rising phase of the residual response and then extrapolated back to the baseline to determine the onset. When so determined, median latencies for the nearest viewing ranged from 16.4 to 18.5 ms, values appreciably shorter than any in the literature.

Acceleration↗
PubMed2005

Eye movements in chorea-acanthocytosis.

PURPOSE: To describe the eye movement abnormalities in patients with chorea-acanthocytosis (ChAc), a form of neuroacanthocytosis. This autosomal recessive, neurodegenerative disorder with aberrant erythrocyte morphology (acanthocytosis) is caused by mutations in the VPS13A gene. In contrast to Huntington's disease (for which ChAc has occasionally been mistaken), ocular involvement in ChAc has not been systematically studied. METHODS: Three patients aged 26, 30, and 44 years with ChAc and six normal volunteers aged 31 to 48 years were included. Patients had dystonia, chorea, parkinsonism, dysarthria, dysphagia, seizures, cognitive abnormalities, and acanthocytosis. All had heterozygous VPS13A mutations and degeneration of the basal ganglia on magnetic resonance imaging (MRI) typical of ChAc. Patients had an extensive clinical and laboratory work-up. Neuro-ophthalmic examinations and eye movement recordings made with the magnetic search coil technique assessed patients' fixation characteristics, horizontal and vertical saccades, pursuit, and antisaccades. These were compared to the data of control subjects. RESULTS: Patients exhibited more than 30 square-wave jerks (small saccadic intrusions) per minute, versus 0 to 8 in the control subjects, as well as fractionated (multistep) and hypometric horizontal and vertical saccades. Decreased saccadic peak-velocity and reduced saccadic range were more pronounced for vertical saccades. Pursuit testing performed in two patients showed low gain. Results of antisaccade testing done in one patient were abnormal. CONCLUSIONS: The findings suggest brain stem involvement as an additional site of neurodegeneration outside the basal ganglia in ChAc. Patients with this progressive, intractable disease have pronounced ocular motor abnormalities. Eye movement recordings could assist in diagnosing ChAc, monitoring its progression and possible treatment evaluation.

Adult↗
PubMed2006

The role of eye movements in visuo-manual adaptation.

The present study evaluated the role of eye movements for manual adaptation to reversed vision. Subjects tracked a visual target using a mouse-driven cursor. In Experiment A, they were instructed to look at the target, look at the cursor, fixate straight ahead, or received no instructions regarding eye movements (Groups T, C, F, and N, respectively). Experiment B involved Groups T and C only. In accordance with literature, baseline manual tracking was more accurate when subjects were instructed to move their eyes rather than to fixate straight ahead. In contrast, no such benefit was observed for the adaptive improvement of tracking. We therefore concluded that transfer of information from the oculomotor to the hand motor system enhances the ongoing control of hand movements but not their adaptive modification; probably because the large computational demand of adaptation does not allow an additional processing of supplementary oculomotor signals. We further found adaptation to be worse in T than in any other group. In particular, adaptation was worse in T than in C although eye movements were the same: subjects in both groups moved their eyes in close relationship with the target rather than the cursor, Group C thus disobeying our instructions. The deficient performance of Group T is therefore not related to eye movements per se, but rather to our instructions. We conclude that an independently moving target strongly attracts eye movements independent of instruction (i.e. Groups T and C), but instructions may redirect spatially selective attention (i.e. Group T vs C), and thus influence adaptation.

Adaptation, Physiological↗
PubMed1992

Blurring by fixational eye movements.

A complete description of the loss of contrast sensitivity at high spatial frequencies requires an estimate of the role of eye movements, which could blur fine detail. We describe a new technique to isolate their effect. Observers viewed either a 100 c/deg interference fringe, which the cone mosaic aliased to a low frequency zebra stripe, or an artificial zebra stripe. The real and artificial zebra stripes have similar spatial patterns, but differ in the temporal modulation produced by eye movements. Contrast threshold was measured as a function of duration for both stimuli flashed in the dark. The ratio of the contrast thresholds for the real and artificial zebra stripes with long durations, when eye movements could have a differential effect, is always within a factor of two or so of the ratio for 1 msec flashes, when eye movements are eliminated. These results support the view that eye movements are only a minor source of image degradation even at very high spatial frequencies, and provide no support for the view that they improve high resolution tasks.

Contrast Sensitivity↗
PubMed1996

Quantitative assessment of fixational eye movements by scanning laser ophthalmoscopy.

A new method for quantifying fixational eye movements by scanning laser ophthalmoscopy was developed and the method was evaluated in ten normal persons. Video sequences of the ocular fundus obtained during fixation were recorded, and linear movements of the fovea between successive video frames were transformed to angular movements of the eye by an algorithm that takes into account the individual optical properties of the eye. A computer program was developed to automatically calculate the amplitude, the direction, and the duration of the angular movements together with the precision of each of these estimates. Two types of eye movements could be recognized in normal persons; a fast type (saccades) which was initiated and terminated within one video frame (20 msec), and a slow type (drifts) which lasted more than 8 video frames (160 msec). The mean amplitude of the fast movements (0.41 degrees) was significantly higher than the mean amplitude of the slow movements (0.31 degrees). The methods was found to be suitable for quantifying fixational eye movements in clinical trials while simultaneously visualizing the ocular fundus. However, by refining the determination of the foveal position on the SLO images the precision of the method can be further improved.

Adult↗