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PubMed1992

Dynamics and efficacy of saccade-facilitated vergence eye movements in monkeys.

1. Four macaque monkeys were trained to fixate visual targets. Eye movements were recorded binocularly using the search coil technique. Saccades, vergence movements, and combinations of the two were elicited by training the monkeys to alternate the gaze between real visual targets that differed in viewing distance and eccentricity with respect to the monkeys' heads. 2. When they shifted the gaze between targets that were at different viewing distances, the monkeys made vergence eye movements. For targets placed along the midsagittal plane, the monkeys often made binocularly symmetric vergence movements. The peak speed of symmetric divergence movements increased linearly with vergence amplitude by 5.7 deg/s per degree of vergence. The peak speed of symmetric convergence movements increased linearly with vergence amplitude by 7.9 deg/s per degree of vergence. 3. For gaze shifts between targets placed eccentrically with respect to the midsagittal plane and at different viewing distances, the monkeys made saccades in combination with vergence eye movements. When a saccade occurred during a vergence movement, peak vergence eye speed increased abruptly and reached a peak that was proportional to the speed of the saccade. For four monkeys, peak divergence speed ranged from 242 to 315 deg/s and peak convergence speed ranged from 257 to 340 deg/s for 16-deg vergence and 20-deg saccadic eye movements. 4. For gaze shifts between far targets at the same viewing distance but different eccentricities, saccadic eye movements were transiently disjunctive even though there was no vergence requirement. Initially, the eyes diverged and then converged to restore fixation to the correct depth plane. Divergence was followed by convergence regardless of the direction of the saccade. 5. The presence of transient saccade-related disjunctive eye movements suggested that the abrupt increase in peak vergence speed during combined saccadic and vergence eye movements was produced by the linear addition of a vergence eye movement and the saccade-related transients. Consistent with this hypothesis, the rate of change in peak vergence speed during various-sized saccades between far targets (no vergence required) was similar to the rate of change in peak vergence speed during combined saccadic and vergence movements. However, the peak vergence speeds during the combined movements were higher than predicted by the linear addition hypothesis, suggesting the presence of an additional mechanism. 6. The saccade-related increase in peak vergence speed during combined saccades and vergences led to a significant decrease in the amount of time required to complete vergence movements.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2005

An fMRI study of optokinetic nystagmus and smooth-pursuit eye movements in humans.

Both optokinetic nystagmus (OKN) and smooth-pursuit eye movements (SPEM) are subclasses of so-called slow eye movements. However, optokinetic responses are reflexive whereas smooth pursuit requires the voluntary tracking of a moving target. We used functional magnetic resonance imaging (fMRI) to determine the neural basis of OKN and SPEM, and to uncover whether the two underlying neural systems overlap or are independent at the cortical level. The results showed a largely overlapping neural circuitry. A direct comparison between activity during the execution of OKN and SPEM yielded no oculomotor-related area exclusively dedicated to one or the other eye movement type. Furthermore, the performance of SPEM evoked a bilateral deactivation of the human equivalent of the parietoinsular vestibular cortex. This finding might indicate that the reciprocally inhibitory visual-vestibular interaction involves not only OKN but also SPEM, which are both linked with the encoding of object-motion and self-motion. Moreover, we could show differential activation patterns elicited by look-nystagmus and stare-nystagmus. Look-nystagmus is characterized by large amplitudes and low-frequency resetting eye movements rather resembling SPEM. Look-nystagmus evoked activity in cortical oculomotor centers. By contrast, stare-nystagmus is usually characterized as being more reflexive in nature and as showing smaller amplitudes and higher frequency resetting eye movements. Stare-nystagmus failed to elicit significant signal changes in the same regions as look-nystagmus/SPEM. Thus, less reflexive eye movements correlated with more pronounced signal intensity. Finally, on the basis of a general investigation of slow eye movements, we were interested in a cortical differentiation between subtypes of SPEM. We compared activity associated with predictable and unpredictable SPEM as indicated by appropriate visual cues. In general, predictable and unpredictable SPEM share the same neural network, yet information about the direction of an upcoming target movement reduced the cerebral activity level.

Adult↗
PubMed2001

Cortical substrates of perceptual stability during eye movements.

We are usually unaware of retinal image motion resulting from our own movement. For instance, during slow-tracking eye movements, the world around us remains perceptually stable despite the retinal image slip induced by the eye movement. This example of perceptual invariance is achieved by subtracting an internal reference signal, reflecting the eye movement, from the retinal motion signal. If the two cancel each other, visual structures, which do not move, will also be perceived as nonmoving. If, however, the reference signal is too small or too large, a false eye-movement-induced motion of the external world will be perceived. We have exploited our ability to manipulate the size of the reference signal in an attempt to reveal the structures in visual cortex, encoding the perception of self-induced visual motion rather than the retinal motion signal. Using EEG and lately also MEG recordings in human subjects and single-unit recordings in monkeys, we have been able to show that our ability to perceive the world as stationary despite eye-movement-induced retinal image slip is based on "late" parts of the cortical hierarchy of motion processing, sparing the early stages up to cortical area MT and, among others, involving cortex at the junction between the parietal and temporal lobes close to the parieto-insular-vestibular cortex. Lesions of this network in humans render the visual system unable to compensate for the visual consequences of eye movements, giving rise to severe dizziness, whenever the eyes move smoothly.

Animals↗
PubMed1994

[Recording characteristics of the eye mark recorder in measurements of vertical eye movements].

Electronystagmography (ENG) has been widely used in physiological studies of eye movements. It is generally known that ENG is at a disadvantage in recording the vertical component of eye movements, and thus there has been a great deal of difficulty in physiological studies of vertical eye movements using ENG. The eye mark recorder is an instrument which has already been used in the study of visual point movement in various situations. We tried to apply the eye mark recorder to the recording of eye movements in normal volunteers, and then compared its recording characteristics with those of ENG. When recording vertical eye movements with the eye mark recorder there is little baseline drift and no confusing waves caused by blinking, which is sometimes misinterpreted as nystagmus. The result is easy calibration of the device and more accurate measurement of the slow-phase velocity of nystagmus than ENG. Recording with the eye mark recorder is atraumatic and allows binocular visual stimulation. There are certain other techniques, such as search coil or video oculography, which allow more accurate recording of vertical eye movements than ENG. The search coil techniques, however, requires the attachment of a measuring contact lens during the examination and video oculography is still in development process, so both of them are difficult to use widely. Thus, we found that the eye mark recorder has a great advantage in recording the slow-phase eye velocity of vertical nystagmus and the vertical component of smooth eye movements in humans. We think that eye mark recorder can serve as a powerful new tool to investigate vertical OKN and OKAN.

Adult↗
PubMed2004

Eye movements and psychiatric disease.

PURPOSE OF REVIEW: During the past year a number of studies have been published on eye movement dysfunction in patients with psychiatric disease. According to the mainstream of modern neuropsychiatric research, these studies cover either genetic aspects or the results of pharmacological manipulation. RECENT FINDINGS: A few studies addressed impaired smooth pursuit eye movements (eye tracking dysfunction) in unaffected relatives of psychiatric patients, and were important in excluding non-specific effects (e.g. medication) and isolating genetic predisposition to the disease. This predisposition could be demonstrated in families of schizophrenic patients irrespective of whether the index case was sporadic or familial. One large study demonstrated pathological distributions of various parameters of smooth pursuit eye movement performance in groups of schizophrenic patients and their relatives. However, another study challenged the specificity of eye tracking dysfunction as a trait marker for schizophrenia by showing that its prevalence was identical among relatives of patients with affective disorder and schizophrenia. Eye tracking dysfunction was associated with two gene polymorphisms that interfere with dopamine metabolism and are thus reasonable candidate genes for the predisposition to schizophrenia. The influence of nicotine and neuroleptic drugs on eye movement performance was studied in schizophrenic patients. Nicotine improved smooth pursuit performance in three studies, one of which attributed this finding to enhanced attention. Two groups of schizophrenic patients treated with two different atypical neuroleptic drugs, risperidone and olanzapine, did not differ in a battery of saccadic tasks. SUMMARY: Eye movements provide an important tool to measure pharmacological effects in patients and unravel genetic traits in psychiatric disease.

Dopamine↗
PubMed1977

Operant discriminative conditioning of vertical eye movements in the midpontine pretrigeminal cat.

In the acute midpontine pretrigeminal cat, either upward or downward eye movements above a certain preset amplitude were reinforced by electrical stimulation of the lateral hypothalamic (LHT) reward area, which did not induce a significant eye movement by itself. During the course of the reinforcement procedure, eye movements greatly increased. In a yoked control test where LHT stimulation was delivered to a cat, independently of its own eye movements, no significant enhancement of the eye movements was observed. However, when reinforcement was given contingently on each large eye movement, eye movement rate became much higher. When cats were trained for an operant discrimination between an S+ (light-off or light-on) and an S- (light-on or light-off), 5 cats acquired clearly differential responses to the S + and S-. They also learned a discrimination reversal. Furthermore, removal of the visual cue eliminated differential responses during the reinforcement and nonreinforcement periods. These data strongly suggest that, in its preparation, a real learning process in the form of a visual discrimination is maintained and an operant conditioning of eye movements with hypothalamic stimulation was achieved without feedback from the peripheral nerve or caudal central nervous system.

Animals↗
PubMed1994

Pain ameliorating effect of eye movement desensitization.

This study explores the efficacy of eye movement desensitization and reprocessing (EMD/R) in the management of acute pain induced by hand exposures to ice water. Thirty participants were randomly assigned to one of the following interventions: (a) eye movement desensitization and reprocessing, (b) eye movement desensitization with music (EMD/M), and (c) control. The EMD/R participants focused on negative experiences associated with exposure to ice water, generated positive self-talk, and diverted their attention away from pain by focusing on a rapidly moving light on a monitor. The EMD with music group received eye movement desensitization coupled with preferred music. Repeated measures univariate and multivariate analysis of covariance was used to analyze the data. Results indicated that both procedures alleviated participants' pain to a similar degree and significantly more than the control, P < 0.05.

Adolescent↗
PubMed1975

Eye movements under different rehearsal strategies.

Eye movements were recorded while subjects studied lists of simultaneously presented words. The 24 subjects in the storage group studied for immediate recall, and the 24 subjects in the coding group studied primarily for a later, final recall. Those subjects in the coding group had longer eye fixations and fewer regressions than did subjects in the storage group. In addition, the subjects in the coding group recalled fewer words in immediate recall and more words in final recall than did the subjects in the storage group. These results were interpreted as supporting the elaboration hypothesis of coding in rehearsal, which states that coding into long-term store consists of rehearsing both old and new information in short-term store. The results did not support the concentration hypothesis, which states that coding into long-term store consists of intensively rehearsing a smaller number of items than rehearsed under a storage strategy. The eye movement data also indicate that subjects read about twice as many words as they overtly rehearse.

Adolescent↗
PubMed1979

[A case of "ping-pong ball eye movement (author's transl)].

We experienced a rare and peculiar eye movement in a comatose patient with ruptured intracranial aneurysm. The patient's eyes moved quickly and irregulary from one extreme position to the other with whirling and bounding components. Such abnormal eye movement occasionally halted, but abruptly reappeared. We named this abnormal eye movement which had never been reported before, "ping-pong eye movement". Neuropathological study revealed a subarachnoid hemorrhage and the diffuse infarction in the right remporal lobe, and a smal clot in the fourth ventricle without specific findings in the brainstem and the cerebellum. Consideration was made that the hemorrhage in the fourth ventricle resulted in a hyper-irritable state in the fastigial nuclei, from which the abnormal discharges were driven to the reticular formation, the vestibular nuclei, the MLF, and the oculomotor complexes. We conclude that this "ping-pong" ball eye movement" might be the appearance of epilepsy in the eyes, due to the epileptogenic focus of the fastigial nuclei.

Eye Movements↗
PubMed1984

Activity of the striate cortex cells during saccadic eye movements of the alert cat.

Neuronal activity in the striate cortex was studied during eye movements of alert cats under reinforcement of eye movements with rewards of water. Striate cells were differentiated into two groups exhibiting contrasting activities during and at intermissions of saccadic eye movements made in the presence of a visual pattern: (1) saccade-excited (SE) cells (207/271) that were excited during saccadic eye movements and were much less active at intermissions; and (2) saccade-depressed (SD) cells (55/271) that were depressed during eye movements and were strongly active at intermissions. Under suppression of eye movements by retrobulbar paralysis or by withdrawal of the rewards, most SE-cells (89/104) exhibited photic responsiveness characteristic of "complex" cells in the anesthetized cat, and almost all SD-cells (23/26) that of "simple" cells. Therefore, it is likely that the two major neuronal populations in the striate cortex provide parallel channels of visual information which are gated in an alternative way during eye movements.

Animals↗
PubMed1985

Properties of visual inputs that initiate horizontal smooth pursuit eye movements in monkeys.

Smooth pursuit eye movements allow primates to fixate and track small, slowly moving objects. Pursuit usually requires visual targets; our aim was to determine the properties of the visual signals transmitted to the pursuit motor system. Rhesus monkeys were rewarded for tracking spots of light that underwent discreet changes in velocity under a variety of visual conditions. We measured the resulting smooth eye acceleration in a 100-msec interval that began with the initiation of pursuit and ended before there had been time for visual feedback. This approach allowed us to vary the parameters of visual stimulation and measure eye movement responses in a way that provides estimates of the properties of signals transmitted by visual pathways. The initiation of pursuit showed different properties early and late in the interval we studied. In the first 20 msec of pursuit, eye acceleration was in the correct direction, but was independent of the initial position of the moving images, the velocity of the stimulus, or the presence or absence of background illumination. Thereafter, the initiation of pursuit depended strongly on all of the above parameters. Eye acceleration was highest when the moving images fell close to the fovea and decreased sharply as eccentricity was increased up to 21 degrees. When the background was diffusely illuminated, eye acceleration showed velocity selectivity; it was highest for a middle range of velocities (30 to 60 degrees/sec) and decreased for higher velocities. When the background was dark, eye acceleration increased as a function of target velocity up to 150 degrees/sec. We conclude that the initiation of pursuit has at least 2 visual components. The two components have different latencies and show quite different relationships to the visual properties of the stimulus, suggesting two cell populations that could provide the visual inputs for pursuit.

Animals↗
PubMedDate not supplied

Eye movements can control localized image enhancement and analysis.

The eye movements of a reader during interpretation of digital chest radiographs can provide valuable information for lesion detection. Measures of eye movements (e.g., the locations and durations of gaze dwells) are associated with detection accuracy. During image interpretation, the reader's eye movements are tracked unobtrusively with a video camera mounted below the monitor displaying the images. The eye movement information is used to identify regions of prolonged dwell, which are associated with false-positive detection of pulmonary nodules. Based on the locations of the dwell regions, a small, circular region of interest is created within the image. Real-time digital processing can then be performed within this region of interest. Such processing can be performed as the reader is looking at the image or after the image has been interpreted. Readers' eye movements can be used to direct localized image enhancement and analysis during interpretation of digital chest radiographs.

Eye Movements↗
PubMed1979

Minute eye movement during sleep.

The minute eye movements of 4 sleeping subjects were studied with a piezo-electric strain-gauge transducer. The frequency and amplitude of ocular microtremor activity diminished during sleep. Activity increased after auditory stimulation and with the appearance of a K complex in the EEG. The ocular microtremor activity also increased with the onset of rapid eye movement (REM). Low amplitude 'micronystagmoid' movements were observed at intervals throughout sleep. In contrast to the changes observed during sleep, ocular microtremor activity did not diminish during hypnosis. The transducer was far more sensitive than the conventional EOG recording system.

Acoustic Stimulation↗
PubMed1983

Dyslexic and normal readers' eye movements.

Dyslexic and normal readers' eye movements were compared while tracking a moving fixation point and in reading. Contrary to previous reports, the dyslexic and normal readers did not differ in their number of saccades, percentage of regressions, or stability of fixations in the tracking task. Thus, defective oculomotor control was not associated with or a causal factor in dyslexia, and the dyslexics' abnormal eye movements in reading must be related to differences in higher cognitive processes. However, individual differences in oculmotor efficiency, independent of reading ability, were found within both the dyslexic and normal groups, and these differences were correlated in reading and tracking tasks.

Adolescent↗
PubMed1993

Horizontal and vertical reading: a comparative investigation of eye movements.

Electronystagmographic (ENG) recordings of eye movements were made during the horizontal and vertical reading of a standardized text. The text was rotated to one side through an angle of 90 degrees for vertical reading. A total of 35 normal subjects was investigated under identical conditions. The following differences were found: A "staircase" pattern of successive, remarkably regular eye jerks was observed during horizontal reading. The reading speed was significantly higher in the horizontal direction. Vertical eye movements during vertical reading were less regular and showed a greater number of small jerks of varying size. No significant difference in reading speed between the two vertical directions was found. The search coil method (Robinson), which was employed in one subject, yielded much more accurate recordings than did the ENG. As a control experiment for vertical reading, the letters were rotated through 90 degrees. Reading this transposed text took twice as long as reading a 90 degrees-rotated text.

Adult↗
PubMedDate not supplied

The dual nature of lateral eye movements.

This study investigated the validity of lateral eye movements (LEM) as a measure of the individual differences and task demands aspects of LEM by comparing eye movements to information questions that had no clear hemispheric locus with eye movements to rhyme questions that demanded specific left hemisphere involvement. Fifty subjects were asked to respond to the two types of questions and the initial direction of their eye movement was recorded. The results indicated that LEM are a reliable measure of individual differences because both test-retest and split half reliabilities were high (.78 to .85). LEM were also shown to be responsive to task demands. The number of leftward LEM did not differ from rhyme and information questions, but there were more rightward LEM and fewer stares to the rhyme question. These results suggest that LEM are a reliable individual difference measure and are sensitive to task differences. There is clear evidence that LEM have neuropsychological implications, but every task demands the integrated functioning of the whole brain and these implications should not be overgeneralized.

Adolescent↗
PubMedDate not supplied

Initial tracking conditions modulate the gain of visuo-motor transmission for smooth pursuit eye movements in monkeys.

Smooth pursuit eye movements allow primates to keep gaze pointed at small objects moving across stationary surroundings. In monkeys trained to track a small moving target, we have injected brief perturbations of target motion under different initial conditions as probes to read out the state of the visuo-motor pathways that guide pursuit. A large eye movement response was evoked if the perturbation was applied to a moving target the monkey was tracking. A small response was evoked if the same perturbation was applied to a stationary target the monkey was fixating. The gain of the response to the perturbation increased as a function of the initial speed of target motion and as a function of the interval from the onset of target motion to the time of the perturbation. The response to the perturbation also was direction selective. Gain was largest if the perturbation was along the axis of ongoing target motion and smallest if the perturbation was orthogonal to the axis of target motion. We suggest that two parallel sets of visual motion pathways through the extrastriate visual cortex may mediate, respectively, the visuo-motor processing for pursuit and the modulation of the gain of transmission through those pathways.

Animals↗
PubMed1975

Eye movements in Daphnia pulex (De Geer).

1. The various types of eye movement exhibited by the cyclopean eye of Daphnia pulex were studied using high speed motion photography. 2. This rudimentary eye, which consists of only 22 ommatidia, can move through approximately 150 degrees in the sagittal plane and 60 degrees in the horizontal plane. 3. Four classes of eye movement were found: (1) a high speed tremor at 16 Hz with an amplitude of 3-4 degrees, which resembles physiological nystagmus, (2) a slow rhythmic scanning movement at 4 Hz, and 5-6 degrees amplitude, (3) large fast eye movements similar to saccadic eye movements and (4) optokinetic nystagmus produced by moving striped patterns. 4. Where the fast tremor occurred concurrently with the slow rhythmic scan, a Fourier analysis revealed that the former was the fourth harmonic of the latter.

Animals↗