Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Eye Movements”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed1986

The importance of eye movements in the analysis of simple patterns.

How important are eye movements to visual pattern analysis? Previous findings indicate that at least one visual task (counting) is seriously impaired without them. We asked whether a comparable limitation applies to pattern recognition. Subjects were presented with pairs of randomly generated arrays composed of black and white pixels. The subjects indicated whether the arrays were identical or differed by one pixel. In one experiment, they were instructed to use normal eye movements, in another they were required to fixate on a point between the arrays. When eye movements were permitted, subjects' performance showed evidence for a search in which the discrepant pixel was eventually found, given adequate inspection time. When fixation was required, search was less efficient and the discrepant pixel was sometimes not found, despite prolonged inspection time. These results were independent of target size over a wide range. Our findings indicate that eye movements play a crucial role in pattern analysis that is not related to resolution.

Eye Movements↗
PubMedDate not supplied

Quantification of tracking eye movements in normal subjects.

Voluntary tracking eye movements were analysed in 20 normal subjects whose gaze was fixed on a visual target moving at six different constant velocities between 10 degrees s-1 and 60 degrees s-1. Tracking ability was quantified according to four parameters. The mean value and dispersion of each parameter at each velocity were determined. The maximum velocity gain of smooth pursuit was, on average, 0.98-0.75, gradually diminishing with increasing target velocities of 10-60 degrees s-1. Amplitude of smooth pursuit decreased gradually and was replaced by superimposed saccades at increasing target velocities. Saccades with amplitudes of 3-10 degrees were present at all target velocities, while those greater than 10 degrees occurred mostly at target velocities above 30 degrees s-1. Square waves were rare but equally frequent at all target velocities and seemed to occur randomly during tracking eye movements. An additional group of 9 subjects was investigated twice. Mean values of maximum velocity gain of amplitude of smooth pursuit and of frequency of superimposed saccades were higher on the second occasion, probably reflecting the effect of learning. Co-operation and interaction of the smooth pursuit and the saccadic subsystems to produce the voluntary tracking were discussed.

Adaptation, Ocular↗
PubMed2004

Eye movements evoked by selective saccular nerve stimulation in cats.

OBJECTIVE: Because of technical obstacles in controlling current spread to adjacent peripheral nerve, eye movements evoked by activation of the otolith organs have not been investigated in detail compared to eye movements evoked by activation of the canal organs. We attempted to solve this problem by applying more sensitive methods using fine needle and strictly controlling stimulus current intensity compare with filed potential for selective stimulation. METHODS: Eye movements evoked by selective, unilateral saccular (SAC) nerve stimulation were investigated using both electrooculography (EOG) and video recording in decerebrated cats in the presence or absence of anesthesia. Electrical stimulation was applied to the SAC nerve through implanted acupuncture needles. RESULTS: In the absence of anesthesia and with stimulus intensities less than (3.1 +/- 2.7) x N(1)T, we found supraduction in both eyes or in either the ipsilateral or contralateral eye of different cats. We observed downward eye movements using a stronger stimulus intensity ((6.2 +/- 2.9)) x N(1)T). The threshold for downward eye movements was significantly greater than that for upward eye movements (P < 0.05). In anesthetized cats, only downward eye movements were observed when stimulus intensities less than 10 x N(1)T ((7.8 +/- 2.3) x N(1)T) were used. CONCLUSION: These results confirm the known sacculo-ocular anatomical connections, which are involved predominantly in vertical eye movements. Because the sacculo-ocular connections are relatively weak, the normal supraduction evoked by SAC activation can be easily modified by factors such as level of anesthesia and the method of stimulation.

Animals↗
PubMed1987

The properties of goal-directed eye movements evoked by microstimulation of the cerebellar vermis in the cat.

The properties of eye movements evoked by microstimulation of the cerebellar vermis, lobules V VII, were investigated in encéphale isolé cats. The evoked eye movements tended to reach the same final goal in the orbit irrespective of initial eye position. The goal position depended on stimulus intensity. In contrast with the monkey, the goal of the eye movement lay within the oculomotor range. The goal position of the eye movements evoked by simultaneous stimuli delivered to two sites corresponded with the point which was obtained by the vectorial addition of the two eye movements evoked by the stimulation of each site. These findings suggest that the cat vermal lobules V VII play an important role in the control of horizontal and vertical eye position in the orbit.

Animals↗
PubMed1997

Changes in dorsal neck muscle activity related to imposed eye movement in the decerebrate pigeon.

Movements of the head and eyes are known to be intimately related. Eye position has also been shown to be closely related to the electromyographic activity of dorsal neck muscles; however, extraocular muscle proprioception has not generally been considered to play a part in the control of such movements. We have previously shown that, in the pigeon, imposed movements of one eye modify the vestibular responses of several dorsal neck muscles in ways that are dependent on stimulus parameters such as the amplitude and velocity of imposed eye movement. The present study examines more closely the interactions between imposed eye movements and different muscle pairs. The three neck muscle pairs studied each responded to afferent signals from the extraocular muscles in discrete and specific ways which appeared to be correlated with their different actions. Complementary effects of imposed eye movements in the horizontal plane were seen for both the complexus and splenius muscle pairs, with imposed eye movements in one direction producing the largest inhibition of the ipsilateral muscle's vestibular response and imposed eye movements in the opposite direction the largest inhibition of the contralateral muscle's vestibular response. During roll tilt oscillation (ear-up/ear-down) in the frontal plane, similar complementary effects of imposed eye movement were seen in the complexus muscle pair, but the splenius muscle pair showed little tuning, with similar inhibition for imposed eye movement directed either upwards or downwards. In contrast to these complementary effects, the biventer cervicis muscle pair showed no vestibular modulation during vestibular stimulation in the horizontal plane and their spontaneous activity was not altered by imposed eye movement. During roll-tilt oscillation (ear-up/ear-down) in the frontal plane imposed eye movement directed vertically upwards increased both muscles' vestibular responses and imposed eye movement directed vertically downwards inhibited both muscles' vestibular responses. Section of the ophthalmic branch of the trigeminal nerve (deafferenting the eye muscles) abolished the effects of imposed eye movement on the neck muscle pairs. In conjunction with further control experiments these results provide compelling evidence that proprioceptive signals from the extraocular muscles reach the neck muscles and provide them with a functionally significant signal. We have previously shown that signals from the extraocular muscles appear to be involved in the control of the vestibulo-ocular reflex. It follows from the experiments reported here that proprioceptive signals from the extraocular muscles are also likely to be involved in the control of gaze.

Animals↗
PubMed1977

The effects of pursuit eye movements on single unit activity in cat visual cortex.

The pursuit eye movements were assumed to be an indicator of the time periods when visual information is actively processed. The experiment was performed on cats with pretrigeminal transection of the brain stem. In such preparations only vertical eye movements were preserved. Under these conditions the following eye movements could be evoked by vertical movements of the stimulus at the periphery of the retina. The influence of these movements on the activity of units which had their receptive fields in area centralis was tested. Contralateral eye was immobilized and the position and preferred direction of the units' receptive fields was tested. Significant differences in neuron activity correlated with the pursuit eye movement were found in 22 percent of cells. It is suggested that the effect is due rather to the active state of visual system than to the peripheral stimulation of retina or the information incoming from extraocular muscles.

Animals↗
PubMed1968

Frequency characteristics of the saccadic eye movement.

Using a piecewise linear approach, individual saccadic eye movements have been Fourier decomposed in an attempt to determine the effect of saccadic amplitude on frequency characteristics. These characteristics were plotted in the traditional Bode plot form, showing gain and phase as a function of frequency for various eye movement amplitudes. Up to about one octave beyond the -3 db gain frequency, the limiting system dynamics represented by the saccadic trajectory of a given amplitude may be considered linear and second order. The -3 db gain frequency was used as a measure of bandwidth, and the -90 degrees phase crossover frequency was used as a measure of undamped natural frequency. These two quantities were used to calculate the damping factor. Both bandwidth and undamped natural frequency decrease with increasing saccadic eye movement amplitude. The damping factor shows no trend with amplitude and indicates approximate critical damping. When compared with the normal variation of characteristics for a given movement, the frequency characteristics of fixed-amplitude saccades showed no generalized trends with changes in direction or DC operating level of movement.

Analog-Digital Conversion↗
PubMed2003

Conjugacy of torsional eye movements in response to a head tilt paradigm.

PURPOSE: Vertically skewed eye movements are induced by head tilt toward the shoulder (roll). Because vertical and torsional eye movements are tightly coupled both mechanically and neuronally, the purpose of the present study was to investigate the conjugacy of torsional eye movements during the Bielschowsky head tilt test (BHTT). Furthermore, the purpose was to investigate the influence of different visual and viewing condition on torsional conjugacy. The issue has clinical relevance in interpreting the outcome of the BHTT. METHODS: Eye movement recordings were performed using the infrared three-dimensional video-oculography (3D-VOG) technique. Objective cycloposition of 20 healthy individuals was measured in presumed primary position and in head tilt positions of 15 degrees, 30 degrees, and 45 degrees to the right and left, respectively. The same paradigm was performed under three different viewing conditions: binocularly without spatial orientation and both binocularly and monocularly with spatial orientation. The stimulus used with spatial orientation was a photographic picture of a historic building, whereas the stimulus with no spatial cues consisted of concentric circles. RESULTS: Consistent excyclovergence occurred in all subjects in head tilt. The relative amount increased with head tilt, regardless of the visual stimulus. Maximum excyclovergence was 0.7 degrees in 45 degrees head tilt during monocular fixation. Binocular viewing enhanced the torsion conjugacy by means of vergence stability (SD), whereas spatial visual cues improved the torsional conjugacy only slightly. CONCLUSIONS: Consistent excyclovergence was induced in head tilt. A vestibular origin seems to provide a plausible explanation of the induced torsional disconjugacy, whereas visual feed-back seems plausible in explaining the better conjugacy in binocular viewing.

Adult↗
PubMed1999

Eye movements and spatial working memory in Parkinson's disease.

Mechanisms of spatial working memory and eye movement control were investigated in eight mild to moderate Parkinson's disease patients (PDs). Subjects were presented with a sequence of four targets which had to be memorized and then recalled by moving their eyes to fixate the four locations in the correct order. Two variations on this procedure were used in which either a different sequence of lights was presented on each trial, or an identical sequence of lights was repeated on each trial. In both conditions subjects made memory-guided eye movements in the dark, without any visual cues to eye movement accuracy or the locations of the previously illuminated lights. Analysis of the amplitude of the primary eye movement and final eye position for each step in the sequence showed that PDs made several discrete saccadic eye movements of reduced amplitude before reaching the final eye position (multi-stepping). When a novel target sequence had to be memorized on each trial, the final eye position reached by PDs for each location was also found to undershoot relative to controls. In contrast, when an identical sequence of targets was repeated on each trial, PDs' final eye position was found to be normal, although primary movement amplitudes were still reduced. PDs showed no multi-stepping and normal final eye position gain under conditions for which the target lights in the sequence were illuminated during movement execution. PDs also made an increased proportion of overt errors in target sequence recall. Parallel neuropsychological testing in PDs and controls revealed that error rates in the sequential memory-guided saccade task were significantly correlated with performance in a task thought to be sensitive to spatial working memory dysfunction. The findings suggest that short-term spatial memory representations are disrupted in the early stages of PD.

Aged↗
PubMed1993

Effect of eye position within the orbit on electrically elicited saccadic eye movements: a comparison of the macaque monkey's frontal and supplementary eye fields.

1. We quantitatively compared the effects of eye position within the orbit on saccadic eye movements electrically elicited from two oculomotor areas of the macaque monkey's frontal lobe cortex: the frontal eye field (FEF) and the supplementary eye field (SEF). 2. The effect of eye position on electrically elicited saccades was studied by delivering 70-ms trains of intracortical microstimulation while the monkeys fixated a spot of light. Tests of different fixation points located across a rectangular array were randomly intermixed. Complete experiments were carried out on 38 sites in three FEFs of two monkeys and 59 sites from three SEFs of the same two monkeys. Stimulation currents for the array experiments were usually 10-20 microA above the site threshold; the average current used was 36 microA for FEF and 49 microA for SEF. 3. The magnitude of effect of the initial eye position on the elicited saccade's dimensions was quantified at each site by computing the linear regression of saccadic eye movement displacement on the eye position within the orbit when stimulation was applied. This computation was done separately for the horizontal and vertical axes. We call the resulting pair of regression coefficients "orbital perturbation indexes." Indexes of 0.0 represent elicited saccades that do not change their trajectory with different initial eye positions (constant-vector saccades), whereas indexes of -1.0 represent elicited saccades that end at the same orbital position regardless of initial eye position (goal-directed saccades). 4. The effect of eye position varied across sites. In both FEF and SEF, the orbital perturbation indexes were distributed between approximately 0.0 and -0.5, with the horizontal and vertical indexes highly correlated across sites. 5. The average orbital perturbation indexes were small for both eye fields and were not significantly different. The mean horizontal indexes were -0.13 and -0.16 for SEF and FEF, respectively. The mean vertical indexes were -0.16 and -0.13. Neither SEF versus FEF difference was statistically significant. 6. In both SEF and FEF, sites yielding larger-amplitude saccades generally had larger orbital effects than sites yielding smaller saccades. This relationship accounted for the majority of the variability of the orbital perturbation indexes across sites in both SEF and FEF. 7. These results indicate that SEF and FEF are not distinguished from each other by the orbital dependence of their electrically elicited saccades. Thus they do not confirm the previously hypothesized dichotomy that FEF codes constant-vector saccades and SEF codes goal-directed saccades.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Pathophysiology of rapid eye movements in the horizontal, vertical and torsional directions.

Saccades and fast phases of optokinetic or vestibular nystagmus are rapid eye movements which are generated in the reticular formation of the brain stem. Palsies of rapid eye movement generation therefore always point towards an infratentorial lesion. Two cell assemblies are responsible for the generation of rapid eye movements: the PPRF, which triggers all rapid eye movements and in this sense plays an important coordinating role in addition to generating movements with a horizontal movement component, and the riMLF in the mesencephalon for movements which have a vertical or torsional direction component. As neurone populations are anatomically segregated according to their respective on-directions, focal lesions lead to the loss of rapid eye movements in particular directions (Table 2). Such palsies of rapid eye movement generation which are direction specific can be distinguished from dysmetria, which points towards a cerebellar lesion, or the difficulty to trigger a saccade to a particular target, which can involve cortical systems.

Animals↗
PubMed2006

Preparatory gain modulation of visuomotor transmission for smooth pursuit eye movements in monkeys.

It has been reported that the visuomotor processing underlying the initiation of smooth pursuit eye movement is modulated in relation to the recent experience of eye movements: the initial pursuit eye velocity is larger after experiencing repeated pursuits than saccades. To assess which parameters of the previously executed pursuits play an essential role in modulating the gain of visuomotor transmission, we recorded the ocular responses of monkeys to a brief perturbing motion of the tracking target injected before the start of the eye movements. First, we compared the perturbation responses among the blocks in which the duration of executing pursuit was varied. We found that the response amplitude increased with the increase of the pursuit duration and it reached a plateau level at 100-200 ms of the duration. Second, a comparison of the perturbation responses in the blocks in which target velocity was different showed a gradual increase of the response as a function of the required pursuit velocity. Third, when the animals repeatedly performed pursuits, the response amplitude gradually increased with increasing interval between the appearance of the target and the onset of perturbation. On the other hand, such an increase was not observed when the animals repeatedly performed saccades. These results suggest that before initiating eye movements, the pursuit system modulates the gain of visuomotor transmission so as to be closely related to the properties of the repeatedly experienced eye movements and this gain modulation is triggered by the target's appearance.

Animals↗
PubMed2005

Smooth-pursuit eye movement and directional motion-contrast sensitivity in schizophrenia.

Although the occurrence of visual processing and eye-movement disorders in schizophrenia have been widely recognized, their relationship with the symptoms of schizophrenia is less well understood. In two experiments the relationship between directional-motion processing and smooth-pursuit eye movement was investigated in normal observers and in groups with positive and negative symptoms in schizophrenia. The first experiment measured linear smooth-pursuit eye movement at six target velocities from 5.0 to 30.0 degrees s(-1) and the second experiment measured directional motion-contrast sensitivity at three spatial (1.0, 4.0 and 8.0 c/deg) and five temporal (0.75, 3.0, 6.0, 12.0 and 18.0 Hz) frequencies in the same groups of observers. No significant differences were found between the control and positive-symptom group in directional motion-contrast sensitivity and smooth-pursuit eye movements. In comparison, a relationship was found between a significant reduction in directional motion-contrast sensitivity and significantly reduced smooth-pursuit eye movement in the negative-symptom group and serves to further cleave the distinction between positive and negative symptoms in schizophrenia. The relationship between visual motion processing and pursuit eye movement in the negative-symptom group was explained by a disorder in directional motion processing that fails to fully engage the pursuit eye movement system and reduces smooth pursuit eye-velocity gain.

Adult↗
PubMed1989

[Study in recognition on the face. Affects of eye movement on alternation of the facial appearance].

The following experiment was designed to investigate the affects of eye movements in visual performance on alternation of the facial appearance using Vision analyzer. Major concern in this study was whether a casual relationship between eye movements and alternation of the facial appearance could be established such that eye movements necessarily preceded an alternation of the stimulus perception. Nine students who did not have any dental education and three dentists were selected as subjects. Three stimuli were presented to subjects which were made of the full face photographic slide of adult male with two different vertical dimension of occlusion in complete upper and lower dentures and normal facial height. Subjects were first shown in the normal stimuli, then they were presented with different version of the stimuli and asked to record their percept. Tow condition of instructions were used which elicited different scanning patterns. The results were as follow 1. Evidence that individual differences in eye movement patterns were existed. 2. Before instruction, their eye movements in visual performance tend to be dispersed all over the face. 3. After instruction, they were able to clearly identify altered facial appearances with good understanding of anatomical facial form. 4. Dentists were able to evaluate the altered facial appearances focusing their anatomical knowledge. The present investigation has demonstrated that the study of eye movements scanning strategies involved in two-dimensional face comparison and recognition is fruitful area of research.

Eye Movements↗
PubMed1997

Patterns of eye movements during parallel and serial visual search tasks.

Eye movements were monitored while subjects performed parallel and serial search tasks. In Experiment 1a, subjects searched for an "O" among "X"s (parallel condition) and for a "T" among "L"s (serial condition). In the parallel condition in Experiment 1b, "[symbol: see text]" was the target, and "O"s were distractors; in the serial condition these stimuli switched roles. Displays contained 1, 12, or 24 stimuli, with both target-present and target-absent trials. RT and eye-movement measures (number of fixations, saccadic error, and latency to move) indicated that search efficiency was greatest in the parallel conditions, followed by the serial condition of experiment 1a and, finally, by the serial condition of Experiment 1b. This suggests that eye movements are correlated with the attentional processes underlying visual search.

Attention↗
PubMed2004

Convergence eye movements evoked by microstimulation of the rostral superior colliculus in the cat.

Results of our previous studies suggest that the circumscribed area in the rostral superior colliculus (SC) of the cat is involved in the control of accommodation. Accommodation is closely linked with vergence eye movements. In this study, we investigated whether or not vergence eye movements are evoked by microstimulation of the rostral SC in the cat. In addition, we studied the effect of chemical inhibition of the rostral SC on visually guided vergence eye movements. This study was conducted on three cats, weighing 2.5-3.5 kg. The animals were trained to carry out visually guided saccade and convergence tasks. Eye movements were measured using search coils placed on both eyes. We recorded eye movements evoked by microstimulation of the rostral SC in the alert cats. Muscimol was injected into the rostral SC, and the effect of SC inactivation on visually guided vergence eye movements was investigated. Convergence eye movements were evoked by low-current stimulation (< 30 microA) of a circumscribed area in the intermediate layers of the rostral SC on one side. Spontaneous saccades were interrupted by the stimulation of the low-threshold area for evoking convergence. Visually guided convergence eye movements were severely diminished by the injection of muscimol into the low-threshold area for evoking convergence of the SC. The rostral SC is related to the control of vergence eye movements as well as accommodation. The rostral SC may be involved in the functional linkage between accommodation, convergence and visual fixation.

Action Potentials↗
PubMed1987

Sensitivity of smooth eye movement to small differences in target velocity.

The precision of smooth pursuit eye movements was described by means of a new dependent measure, the "oculomotor difference threshold" (analogous to the perceptual difference threshold) which represents the smallest difference in target velocity that produces statistically distinguishable differences in eye velocity. Oculomotor difference thresholds for constant velocity motions were largest (greater than 50% of target velocity) during the initial 200 msec of target motion, despite fairly high average gains (0.7-1.4) during the same period. Oculomotor difference thresholds declined over time. By about 600-700 msec after the onset of target motion they reached values as low as the perceptual difference thresholds measured psychophysically with the same target velocities. The similarity of the difference thresholds suggests that equally precise sensory representations of target velocity influenced perception and smooth eye movements. Nonsensory influences on smooth eye movement were also found. Smooth pursuit velocity: (1) depended on the velocity of targets in preceding trials; (2) was decreased during the initial 200 msec of target motion when the duration of motion was reduced from 1 sec to 200 msec, a result which shows that high initial pursuit velocity depends on the expectation that pursuit will continue. These effects of context and expected duration allowed the eye to achieve quickly a velocity close to that of the target it was most likely to encounter. Study of the precision of pursuit may be valuable for characterizing its sensory input, but study of the effects of the context in which a stimulus appears and the effects of expectations about future target motion may be more valuable for understanding how smooth eye movements guarantee retinal image velocities optimal for vision.

Eye Movements↗
PubMed1977

Selective attention and eye movements while viewing reversible figures.

This study suggests that different eye-movement patterns are associated with reversals of ambiguous figures. The high scanners seem to be more dependent on eye movements for reversals and their recognition of each pattern depends on the sequence and location of fixations; thus shifts of attention appear to be externalized in the form of large, saccadic eye movements. In contrast low scanners are better able to shift attention internally, e.g., by mental restructuring, without large eye movements. We further suggest that scanning behavior associated with reversals may be modulated by stimulus complexity, figures' reversibility, and extrinsic/intrinsic motivational styles.

Adult↗