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PubMed1991

[Correction of EOG with eye movement measured by the eye mark recorder system].

The electrooculogram (EOG) is usually necessary for the subject to fixate two targets alternately at a fixed visual angle. However, in the patients with poor vision, it can be difficult to fixate exactly. In such case, the results can be improved by using both the measurement of real eye position and the measurement of EOGs in combination. In this study, we measured subject's eye position simultaneously with the potential changes around his eyes as the subject pursued alternately two on-and-off visual targets which were horizontally placed on the cylindrical screen at a regular visual angle in front of his eyes. The EOG is obtained from those potential changes. If the difference between the target position and the fixating point can be calculated from the net eye movement measured with an eye camera, the error potential can be derived from this difference. Therefore, exact potential changes are obtained by correcting the measured potentials with the above error potentials. The authors were able to confirm that the potential changes were approximately proportional to the amplitude of saccadic eye movements within about 30 degrees in front of the eyes. Therefore, the simultaneous measurement of the potential changes and the eye position enable measurement of EOG without pursuing the targets by transforming the measured potentials into the exact values corresponding to the constant amplitudes of saccades.

Electrooculography↗
PubMed2005

Anticipating the three-dimensional consequences of eye movements.

Rapid eye movements called saccades give rise to sudden, enormous changes in optic information arriving at the eye; how the world nonetheless appears stable is known as the problem of spatial constancy. One consequence of saccades is that the directions of all visible points shift uniformly; directional or 2D constancy, the fact that we do not perceive this change, has received extensive study for over a century. The problems raised by 3D consequences of saccades, on the other hand, have been neglected. When the eye rotates in space, the 3D orientation of all stationary surfaces undergoes an equal-and-opposite rotation with respect to the eye. When presented with a an optic simulation of a saccade but with the eyes still, observers readily perceive this depth rotation of surfaces; when simultaneously performing the corresponding saccade, the 3D orientations of surfaces are perceived as stable, a phenomenon I propose calling 3D spatial constancy. In experiments presented here, observers viewed ambiguous 3D rotations immediately before, during, or after a saccade. The results show that before the eyes begin to move the brain anticipates the 3D consequences of saccades, preferring to perceive the rotation opposite to the impending eye movement. Further, the anticipation is absent when observers fixate while experiencing optically simulated saccades, and therefore must be evoked by extraretinal signals. Such anticipation could provide a mechanism for 3D spatial constancy and transsaccadic integration of depth information.

Depth Perception↗
PubMed1996

Properties of eye movements induced by activation of neck muscle proprioceptors.

BACKGROUND: We have previously reported that neck muscle vibration can induce visual illusory movements and eye movements under subdued ambient illumination in human subjects with the head and body fixed. The subjects viewed a fixation light with one eye and the other eye was covered. The eye movements were recorded with an infrared system mounted in goggles attached to the head of the subject. METHODS: In order to further examine the properties of these cervico-ocular reactions and reveal any artefacts in the eye movement recordings, we have studied (1) the effect of increasing the ambient light, which made visual illusory movements disappear, (2) the timing between the illusory movement and the eye movement in subdued light, (3) the effect of viewing the target through a pin-hole, which would reveal artefacts due to head movement, and (4) the effect of mounting the eye movement recording system on the head support, which would allow recording to the absolute eye position change. RESULTS: The results of these experiments showed no significant difference from those that were reported previously. Eye movements of about the same amplitude were induced in both eyes under all conditions, and there was no time difference in the occurrence of visual illusory movements and eye movements. CONCLUSION: The results of this study confirm that neck muscle vibration can induce eye position changes. This seems to confirm that the proprioceptive messages originating in the neck muscles are processed together with visual information of eye position in determining gaze direction.

Adult↗
PubMed2003

Spatiotopic temporal integration of visual motion across saccadic eye movements.

Saccadic eye movements pose many challenges for stable and continuous vision, such as how information from successive fixations is amalgamated into a single precept. Here we show in humans that motion signals are temporally integrated across separate fixations, but only when the motion stimulus falls either on the same retinal region (retinotopic integration) or on different retinal positions that correspond to the same external spatial coordinates (spatiotopic integration). We used individual motion signals that were below detection threshold, implicating spatiotopic trans-saccadic integration in relatively early stages of visual processing such as the middle temporal area (MT) or V5 of visual cortex. The trans-saccadic buildup of important congruent visual information while irrelevant non-congruent information fades could provide a simple and robust strategy to stabilize perception during eye movements.

Adult↗
PubMed1988

The role of the posterior vermis of monkey cerebellum in smooth-pursuit eye movement control. I. Eye and head movement-related activity.

1. The observation of smooth-pursuit eye and retinal image velocity signals in lobules VI and VII of the vermis has given rise to the hypothesis that a neural correlate of a target velocity signal exists in this region of the cerebellum (29). However, activity signaling head velocity is also required to regenerate a target velocity signal. Vermal Purkinje cell activity was, therefore, recorded during the performance of paradigms designed to dissociate head movement-related responses. 2. The activity of 107 Purkinje cells was found to be related to horizontal head velocity. Of these, 52% increased their discharge rate for ipsilaterally directed passive head movement (type I), and 48% were excited by contralateral head movements (type II). 3. In five Purkinje cells in which sufficient data were obtained, cell discharge rate increased monotonically with head velocity over the range of 5-40 deg/s. The sensitivity to head velocity at 0.4 Hz +/- 25 deg/s averaged approximately 0.5 spikes.s-1/deg.s-1 in a larger sample of cells (n = 39). The sensitivities to head velocity, at this same frequency and velocity, of type I and type II Purkinje cells were comparable at 0.44 and 0.51 spikes.s-1/deg.s-1, respectively. 4. The Purkinje cell responses led head velocity by an average of 12 degrees at 0.4 Hz +/- 25 deg/s of passive head rotation. The phase shifts associated with type I and II responses were similar with phase leads of 13 and 9 degrees with respect to head velocity, respectively. 5. A linear interaction of smooth-pursuit eye and head velocity signals was observed during the performance of a variety of antiphase and inphase eye and head movement paradigms. The results support the conclusion that some Purkinje cells in lobules VI and VII of the cerebellar vermis encode a gaze velocity signal. Contributions of the head velocity signal to the regeneration of target velocity are considered in a companion paper (32).

Animals↗
PubMed1992

On identification of saccades from sinusoidal eye movement signals.

Sinusoidal eye movements and potential saccadic eye movements are examined using the syntactic pattern recognition method presented previously. A few computer tests are presented for the verification of potential saccades from signals of sinusoidal eye movements. The technique was developed and tested with electro-oculographic signals. The verification of saccades consists of three tests: the estimation of average noise peaks in an eye movement signal; an angular velocity threshold; and the comparison between a sinusoidal eye movement signal and the corresponding stimulus signal. The technique is also efficient for noisy signals of eye movements, which were stimulated by both predictive and non-predictive sinusoidal stimulus movements.

Calibration↗
PubMed2000

Are better eye movements an advantage in ball games? A study of prosaccadic and antisaccadic eye movements.

The aim of this study was to compare prosaccadic and antisaccadic eye movements of experts in ball sports and controls. In the prosaccadic and antisaccadic task, subjects made saccades respectively towards and away from a suddenly appearing stimulus. By means of infrared-oculography, we compared horizontal eye movements of experts (n=18) and controls (n=20). Experts had shorter overall saccadic latencies, but significantly shorter latencies occurred only on the antisaccade task, not on the prosaccade task. Our findings seem to support the concept that prosaccades and antisaccades have different underlying mechanisms and that expertise in ball games mainly improves antisaccadic performance in terms of latency and variability.

Adult↗
PubMed1984

Historical note on sleep and eye movements.

Involuntary eye movements at the onset of sleep are mentioned in Virgil's Aeneid (19 BC). "Nystagmus" in relation to states of lowered consciousness was painstakingly catalogued by Sauvages (1768). Sporadic studies of eye behavior during sleep were recorded during the 19th century and were associated with disorders of brainstem physiology, culminating in von Economo's observations during the encephalitis lethargica epidemic of the 1920s.

England↗
PubMed2006

Eyes always attract attention but gaze orienting is task-dependent: evidence from eye movement monitoring.

Eyes and gaze are central to social cognition but whether they attract attention differently depending on the task is unknown. Here, the shift in attention towards the eye region and gaze direction of a perceived face was studied in two tasks by monitoring eye movements. The same face stimuli in front- or 3/4-view, with direct or averted gaze, were used in both tasks. In the Gaze task, subjects performed an explicit gaze direction judgment (gaze straight or averted) while in the Head task they performed a head orientation judgment (front- or 3/4-view). Gaze processing was evident in both tasks as shown by longer RTs and lower accuracy when head and gaze directions did not match. In both tasks the eye region was the most attended area but the amount of viewing was task-dependent. Most importantly, approximately 90% of the initial saccades landed in the eye region in the Gaze task but only approximately 50% of them did so in the Head task. These saccades were made in the direction signaled by gaze in the Gaze task but in the direction signaled by head orientation in the Head task. Altogether, these task-modulated behaviors argue against a purely exogenous and automatic orienting-to-gaze mechanism. Based on patient work and neuroimaging studies of gaze processing, we suggest that this task-dependent orienting behavior is rather endogenous and subtended by cortical areas amongst which frontal regions play a central role. We discuss the implications of this finding for clinical populations.

Adult↗
PubMed2005

Spatial object representation and its use in planning eye movements.

The eye movements we make to look at objects require that the spatial information contained in the object's image on the retina be used to generate a motor command. This process is known as sensorimotor transformation and has been generally addressed using simple point targets. Here, we investigate the sensorimotor transformation involved in planning double saccade sequences directed at one or two objects. Using both visually guided saccades toward stationary objects and objects subjected to intrasaccadic displacements, and memory-guided saccades, we found that the coordinate transformations required to program the second saccade were different for saccades aimed at a new target object and saccades that scanned the same object. While saccades aimed at a new object were updated on the basis of the actual eye position, those that scanned the same object were performed with a fixed amplitude, irrespective of the actual eye position. Our findings demonstrate that different abstract representations of space are used in sensory-to-motor transformations, depending on what action is planned on the objects.

Adult↗
PubMed1984

Oculomotor function in Wernicke-Korsakoff's syndrome: I. Saccadic eye movements.

Saccadic eye movements from three patients diagnosed as having Korsakoff's syndrome and one patient who had suffered the acute Wernicke stage of the disorder were examined for changes in saccadic characteristics. The three Korsakoff patients showed increased saccadic latencies; two of the three also had reduced saccadic peak velocities and increased saccadic durations. A higher than expected incidence of hypometric saccades was also found in all four patients; saccadic intrusions were recorded in two Korsakoff patients. These abnormal oculomotor responses were found 2-7 years after the onset of the Korsakoff's syndrome and are consistent with the cerebellar and frontal lobe dysfunction reported in this patient group.

Alcohol Amnestic Disorder↗
PubMed2006

Vowel processing during silent reading: evidence from eye movements.

Two eye movement experiments examined whether skilled readers include vowels in the early phonological representations used in word recognition during silent reading. Target words were presented in sentences preceded by parafoveal previews in which the vowel phoneme was concordant or discordant with the vowel phoneme in the target word. In Experiment 1, the orthographic vowel differed from the target in both the concordant and discordant preview conditions. In Experiment 2, the vowel letters in the preview were identical to those in the target word. The phonological vowel was ambiguous, however, and the final consonants of the previews biased the vowel phoneme either toward or away from the target's vowel phoneme. In both experiments, shorter reading times were observed for targets preceded by concordant previews than by discordant previews. Implications for models of word recognition are discussed.

Attention↗
PubMed2005

Semantic evaluation of syntactic structure: evidence from eye movements.

An eye movement study of temporarily ambiguous closure sentences confirmed that the early closure penalty in a sentence like While John hunted the frightened deer escaped is larger for a simple past verb (hunted) than for a past progressive verb (was hunting). The results can be explained by the observation that simple past tense verbs convey an external viewpoint on an event, which presumably fits best when the event described has an endpoint. A definite description object supplies an endpoint. Consequently, to give up the late closure analysis of the post-verbal object when the verb is in the simple past tense, the processor is abandoning an analysis with semantically-expected properties for one which is not as good semantically. By contrast, a progressive verb denotes an activity which does not require an endpoint and therefore is neutral with respect to whether or not it takes an object.

Eye Movements↗
PubMed1996

Corticocortical input to the smooth and saccadic eye movement subregions of the frontal eye field in Cebus monkeys.

1. The locations and connections of the smooth and saccadic eye movement subregions of the frontal eye field (FEFsem and FEFsac, respectively) were investigated in seven hemispheres of five Cebus monkeys. The supplementary eye field was also mapped in seven hemispheres and the hand/arm regions of the dorsal and ventral premotor areas were localized in five hemispheres. Monkeys were immobilized during experiments with Telazol, a dissociative anesthetic agent that has no significant effect on microstimulation-induced eye movement parameters (threshold, velocity, and duration). The functional subregions were defined with the use of low threshold intracortical microstimulation (current < or = 50 microA). Then different retrogradely transported fluorescent tracers were placed into these functionally defined regions. 2. The FEFsac in Cebus monkey is in the same location as the one in macaque monkeys, which is in Walker's areas 8a and 45. The FEFsem is located in the posterior shoulder of the superior arcuate sulcus near its medial tip and is therefore more accessible for tracer injections than the one in macaque monkeys. This subregion is within cytoarchitectural area 6a beta, which is distinct from the adjacent area 6a alpha (dorsal premotor area). This smooth eye movement subregion may be comparable with the one in macaque monkeys. 3. Cortical connection patterns of the FEFsac and FEFsem are similar and parallel to each other. The predominant neural input to these two subregions originates in other cortical eye fields, including the supplementary eye field, the parietal eye field, the middle superior temporal area, and the principal sulcus region. These cortical eye fields each contain two separate, almost non-overlapping, distributions of labeled neurons that project to the corresponding frontal eye field (FEF) subregions. These results suggest that there may be similar, but relatively independent, parallel corticocortical networks to control pursuit and saccadic eye movements. The weak connections between the middle temporal area (MT) and FEF suggest that the MT may not provide the major source of visuomotion inputs to the FEF, but that it rather plays a role in mediating visual information that is relayed from the striate and extrastriate cortices via MT to the parietal cortex and then to the FEF. In addition to the well-known neural connections between the lateral intraparietal area and the FEF, additional parietal projections have been demonstrated from the dorsomedial visual area area specifically to the FEFsac and from area 7m specifically to the FEFsem.

Animals↗
PubMed1980

Visual field accuracy and eye movement direction: a child's eye view.

Post-exposural eye movements were studied in 32 adults and 24 7-yr.-old children. Stimuli were binary figures exposed tachistoscopically in both visual fields simultaneously. The data showed significant correlations between direction of eye movement and locus of recognition for both children and adults. No significant differences were found in frequencies of eye movements of children and adults. The data are interpreted in terms of the facilitative effects of post-exposural eye movements upon perception for both groups.

Adult↗