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PubMed1990

[Left-sided extremity myorhythmia and rightward slow eye movement caused by a hemorrhage in the right pontine tegmentum].

A sixty-year-old man was admitted to our hospital on January, 1989. He had suffered a hemorrhage in the right side of pontine tegmentum on April, 1988. He had been in deep coma for about a week, and then he had showed diplopia, mild right deafness, right facial palsy, left hemiparesis, dysarthria, dysphagia, and urinary disturbance. He showed slight improvement of these symptoms and signs, but had developed thereafter extremity myorhythmia on the left side. On admission, rightward slow eye movement (absence of saccadic eye movement and preservation of pursuit eye movement of both eyes) was present. MRI revealed a hypointensity lesion with a hyperintensity spot on T2-weighted images showing an old hemorrhage in the right pontine tegmentum and a hyperintensity lesion on T2-weighted images showing an olivary pseudohypertrophy on the right. We concluded that the extremity myorhythmia in this patient was caused by the damage of the right central tegmental tract followed by right olivary pseudohypertrophy. The rightward slow eye movement was considered to be due to the damage of the right paramedian pontine reticular formation and/or its afferent fibers in the pontine tegmentum.

Cerebral Hemorrhage↗
PubMed1998

Eye movement control of computer functions.

The control of computer functions by eye movements was demonstrated in 14 normal volunteers. Electrical potentials recorded by horizontal and vertical electrooculography (EOG) were transformed into a cursor that represented a moving fixation point on a computer display. Subjects were able to spell words and sentences by using eye movements to place the cursor on target letters in the display of an alphabet matrix. The successful demonstration of computer-controlled syntactic construction by eye movements offers a potentially useful technique for computer-assisted communication in special groups, such as developmentally-disabled individuals who have motor paralysis and who cannot speak.

Adult↗
PubMed2006

Eye-movement study and human performance using telepathology virtual slides: implications for medical education and differences with experience.

A core skill in diagnostic pathology is light microscopy. Remarkably little is known about human factors that affect the proficiency of pathologists as light microscopists. The cognitive skills of pathologists have received relatively little attention in comparison with the large literature on human performance studies in radiology. One reason for this lack of formal visual search studies in pathology has been the physical restrictions imposed by the close positioning of a microscope operator's head to the microscope's eyepieces. This blocks access to the operator's eyes and precludes assessment of the microscopist's eye movements. Virtual slide microscopy now removes this barrier and opens the door for studies on human factors and visual search strategies in light microscopy. The aim of this study was to assess eye movements of medical students, pathology residents, and practicing pathologists examining virtual slides on a digital display monitor. Whole histopathology glass slide digital images, so-called virtual slides, of 20 consecutive breast core biopsy cases were used in a retrospective study. These high-quality virtual slides were produced with an array-microscope equipped DMetrix DX-40 ultrarapid virtual slide processor (DMetrix, Tucson, Ariz). Using an eye-tracking device, we demonstrated for the first time that when a virtual slide reader initially looks at a virtual slide his or her eyes are very quickly attracted to regions of interest (ROIs) within the slide and that these ROIs are likely to contain diagnostic information. In a matter of seconds, critical decisions are made on the selection of ROIs for further examination at higher magnification. We recorded: (1) the time virtual slide readers spent fixating on self-selected locations on the video monitor; (2) the characteristics of the ways the eyes jumped between fixation locations; and (3) x and y coordinates for each virtual slide marking the sites the virtual slide readers manually selected for zooming to higher ROI magnifications. We correlated the locations of the visually selected fixation locations and the manually selected ROIs. Viewing profiles were identified for each group. Fully trained pathologists spent significantly less time (mean, 4.471 seconds) scanning virtual slides when compared to pathology residents (mean, 7.148 seconds) or medical students (mean, 11.861 seconds), but had relatively prolonged saccadic eye movements (P < .0001). Saccadic eye movements are defined as eye movements between fixation locations. On the other hand, the pathologists spent significantly more time than trainees dwelling on the 3 locations they subsequently chose for zooming. Unlike either the medical students or the residents, the pathologists frequently choose areas for viewing at higher magnification outside of areas of foveal (central) vision. Eye movement studies of scanning pathways (scan paths) may be useful for developing eye movement profiles for individuals and for understanding the difference in performances between novices and experts. They may also be useful for developing new visual search strategies for rendering diagnoses on telepathology virtual slides.

Biopsy↗
PubMed1977

Lateral eye movements and field-dependence--independence.

The relationship between field-dependence--independence and lateral eye movements was investigated for a sample of 41 male and 39 female right-handed undergraduates. Subjects were administered the Portable Rod-and-frame Test, the Embedded-figures Test, and the Block Design, Object Assembly, and Picture Completion scales of the WAIS. Eye movements in response to 60 questions requiring reflective thought were recorded. Contrary to predictions, right-movers did not perform better than left-movers on the tests of field-dependence--independence. Among males, however, both consistent right- and left-movers performed significantly better than inconsistent movers. The correlation, for males, between lateral eye-movement consistency and a composite measure of field-dependence--independence was .65 (p less than .001). It was argued that eye-movement consistency and cognitive ability level are a joint function of extent of brain lateralization.

Adolescent↗
PubMed2000

Eye movements and reading with plus-lens magnifiers.

PURPOSE: This study aimed to determine the eye movement parameter(s) that is primarily affected when fully sighted subjects use plus-lens magnifiers for reading. METHODS: Two forms of plus-lens magnifier were used: hand-held and spectacle-mounted. Eye movements were recorded using an infrared limbal reflection system as subjects read passages of text with and without the magnifiers. Data were compared for a young age group and an elderly (education-matched) age group. RESULTS: For both age groups, a sawtooth pattern of eye movements was observed and reading speed was significantly (p = 0.0001) reduced when using the magnifiers compared with reading without. Forward saccade length decreased significantly (p = 0.0001) and time for retrace increased significantly (p = 0.0001), but fixation durations were unaffected. The form of magnifier had no significant effect on reading speed or eye movement parameters. CONCLUSIONS: The reduction in reading speed that occurred when using the plus-lens magnifiers was primarily a result of decreased forward saccade length.

Adult↗
PubMed1985

Conjugate lateral eye movements and cognitive mode: blindness as a control for visually-induced oculomotor effects.

The relationship between lateral eye movement directionality and type of cognitive task was investigated in a single blind subject with septo-optic dysplasia. Results from an 80-item test showed that rightward eye movements were significantly associated with verbal tasks and leftward eye movements with spatial tasks. As visual influences on oculomotor behaviour were eliminated, the findings suggested that lateralized eye movements might have arisen as a consequence of asymmetrical activation of cognitive origin triggering the frontal eye field orienting mechanism.

Adolescent↗
PubMed1983

Lateral eye movement as a measure of cognitive ability and style.

Research on lateral eye movements has examined personality and cognitive correlates with the hope of establishing such eye movements as a measure of preference for the different modes of information-processing associated with each of the cerebral hemispheres. Unfortunately, a review of this research provides only conflicting, tenuous substantiation for such hypotheses. The present study attempts to resolve the conflict within previous research by investigating the validity of the measure across a variety of tests of cognitive ability and preference, utilizing several procedures for scoring and classifying subjects on the measure. However, evidence for this measure's ability to predict cognitive performance linked to hemispheric specialization--in any of our conditions--was extremely meager. The usefulness of lateral eye movements as a diagnostic tool must be considered highly suspect; despite this fact, the measure may yet prove to be of some theoretical significance.

Adolescent↗
PubMed1980

Mechanism of hemoglobin desaturation during rapid-eye-movement sleep in normal subjects and in patients with cystic fibrosis.

To assess the mechanism of the decrease in hemoglobin O2 saturation during rapid-eye-movement sleep, we studied 5 normal subjects 22 to 30 yr of age and 20 patients with cystic fibrosis 9 to 29 yr of age. The largest decrease in arterial O2 saturation, as monitored with an ear oximeter during sleep, occurred during rapid-eye-movement sleep, with a mean +/- SEM decrease of 2 +/- 0.31% in the normal subjects and 7.4 +/- 1.3% in the patients in both groups. Rapid-eye-movement sleep was associated with a significant loss of intercostal and diaphragmatic tonic muscle activity (p < 0.01), as monitored with surface electrodes, and a decrease in the baseline position of the rib cage and abdomen, as recorded by magnetometers (p < 0.01). This suggests a decrease in functional residual capacity, which was accompanied by a consistently lower arterial O2 saturation during rapid-eye-movement sleep. Short periods (< 20 s) of inhibition of phasic respiratory muscle activity during rapid-eye-movement sleep were followed by further decreases in arterial O2 saturation. We conclude that the desaturation during rapid-eye-movement sleep in all subjects was mainly due to a decrease in functional residual capacity, leading to airway closure in the dependent lung regions. The hemoglobin desaturation was further aggravated by transient periods of hypoventilation.

Adolescent↗
PubMed1993

Firing behavior of brain stem neurons during voluntary cancellation of the horizontal vestibuloocular reflex. II. Eye movement related neurons.

1. The single-unit activity of neurons in the vestibular nucleus, the prepositus nucleus, and the abducens nucleus, whose activity was primarily related to horizontal eye movements, was recorded in alert squirrel monkeys that were trained to track a small visual target by generating smooth pursuit eye movements and to cancel their horizontal vestibuloocular reflex (VOR) by fixating a head stationary target. 2. The spiking behavior of each cell was recorded during 1) spontaneous eye movements, 2) horizontal smooth pursuit of a target that was moved sinusoidally +/- 20 degrees/s at 0.5 Hz, 3) horizontal VOR evoked by 0.5-Hz sinusoidal turntable rotations +/- 40 degrees/s (VORs), and 4) voluntary cancellation of the VOR by fixation of a head-stationary target during 0.5-Hz sinusoidal turntable rotation at +/- 40 degrees/s (VORCs). The responses of most (28/42) of the units were recorded during unpredictable 100-ms steps in head acceleration (400 degrees/s2) that were generated while the monkey was fixating a target light. The acceleration steps were generated either when the monkey was stationary or when the turntable was already rotating (VORt trials), and the monkey was canceling its VOR (VORCt trials). 3. The firing behavior of all 12 of the abducens neurons recorded was closely related to horizontal eye position and eye velocity during all of the behavioral paradigms used, although there was a small but significant increase in the eye position sensitivity of many of these units when the eye was moving (smooth pursuit) versus when the eye was stationary (fixation). 4. Many neurons in the prepositus nucleus and the medial vestibular nucleus (n = 15) were similar to abducens neurons, in that their firing rate was related primarily to horizontal eye position and eye velocity, regardless of the behavioral paradigm used. These cells were, on average, more sensitive to eye position and smooth pursuit eye velocity than were abducens neurons. 5. The firing rate of 15 other neurons in the prepositus and medial vestibular nucleus was related primarily to horizontal smooth pursuit eye movements. The tonic firing rate of all of these smooth pursuit (SP) cells was related to horizontal eye position, and the majority generated bursts of spikes during saccades in all directions but their off direction. Six of the SP neurons fired in phase with ipsilateral eye movements, whereas the remaining nine were sensitive to eye movements in the opposite direction.(ABSTRACT TRUNCATED AT 400 WORDS)

Abducens Nerve↗
PubMed1995

Single neuron activity in the dorsomedial frontal cortex during smooth pursuit eye movements.

This report describes the behavior of neurons in the dorsomedial frontal cortex during smooth pursuit eye movements. Single neurons were recorded from monkeys while they tracked a small target that moved from the center of a screen outward. The firing rate of most cells was modulated during smooth pursuit eye movements, and often the activity peaked around pursuit initiation. Visual motion of the small target with the eyes fixed could activate pursuit neurons, but did not account for the total pursuit response. Neurons were also selective for the direction in which the animal was tracking, indicating that they were linked to the generation of the eye movements, and not to non-specific arousal effects. The results suggest that the dorsomedial frontal cortex participates in initiating smooth pursuit. It is proposed that the dorsomedial frontal cortex is part of a partial alternative path to the classic pursuit pathway that might be used to facilitate the initiation or control of eye movements beyond a simple reflexive response to retinal slip.

Animals↗
PubMed2005

Influence of gap and overlap paradigms on saccade latencies and vergence eye movements in seven-year-old children.

The latency of eye movements is influenced by the fixation task; when the fixation stimulus is switched off before the target presentation (gap paradigm) the latency becomes short and express movements occur. In contrast, when the fixation stimulus remains on when the target appears (overlap paradigm), eye movement latency is longer. Several previous studies have shown increased rates of express saccades in children; however the presence of an express type of latency for vergence and combined movements in children has never been explored. The present study examines the effects of the gap and the overlap paradigms on horizontal saccades at far (150 cm) and at close (20 cm) viewing distances, on vergence along the median plane, and on saccades combined with convergence or divergence in 15 normal seven-year-old children. The results show that the gap paradigm produced shorter latency for all eye movements than the overlap paradigm, but the difference was only significant for saccades at close viewing distances, for divergence (pure and combined), and for saccades combined with vergence. The gap paradigm produced significantly higher rates of express latencies for saccades at close viewing distances, for divergence, and for saccades combined with divergence; in contrast, the frequencies of express latencies for saccades at far viewing distances and for convergence (pure or combined) were similar in the gap and the overlap paradigms. Interestingly, the rate of anticipatory latencies (<80 ms) was particularly high for divergence in the gap paradigm. Our collective findings suggest that the initiation of saccades at close viewing distances and of divergence is more reflexive, particularly in the gap paradigm. The finding of frequent anticipatory divergence that occurs at similar rates for seven-year-old children (this study) and for adults (Coubard et al., 2004, Exp Brain Res 154:368-381) indicates that predictive initiation of divergence is dominant.

Aging↗
PubMed1994

Treatment of abnormal eye movements that impair vision: strategies based on current concepts of physiology and pharmacology.

Certain abnormal eye movements, especially pathological nystagmus, degrade vision and cause illusory motion of the seen environment. These symptoms are due to excessive movement of images of stationary objects on the retina. Recently, the pathophysiology underlying several types of nystagmus and saccadic oscillations was better defined by the development of animal models and by experimental pharmacological studies. Despite this, few reliable therapies are currently available for these abnormal eye movements. In clinical studies, a number of drugs reportedly helped individual patients, but few drugs have been subjected to double-blind trials. An alternative approach to pharmacological suppression of abnormal eye movements is optical stabilization of images on the retina, which is helpful in selected patients. Weakening of the extraocular muscles, using botulinum toxin or surgery, is prone to cause diplopia and may induce plastic-adaptive changes that render the effect temporary. In some patients, treatment of an underlying condition, such as the Arnold-Chiari malformation, reduces nystagmus and improves vision. There is a need for multicenter trials to evaluate systematically potential treatments of abnormal eye movements that impair vision.

Animals↗
PubMed1999

Effects of dual task demands on the accuracy of smooth pursuit eye movements.

The effect of attention allocation on smooth pursuit eye movements (SPEM) was investigated. Eye movements were electrooculographically recorded in 27 healthy subjects who tracked a visual target that moved horizontally with constant or unpredictably varying velocity. In some trials, subjects performed additional auditory discrimination tasks varying in difficulty. Pursuit error decreased when attention was divided between both tasks. The pattern of results is incompatible with the assumption made in previous research that attention enhancement improves SPEM accuracy. Rather, ocular smooth pursuit appears to be executed in the automatic mode, although intentional and selective processes must contribute. Moreover, controlled attention directed to the tracking task interfered with smooth pursuit. A reinterpretation of earlier studies in which visual monitoring tasks were used to improve eye tracking is needed.

Adult↗
PubMed1992

[The accuracy of saccadic eye movements is associated with their horizontal and vertical direction].

Electro-oculagraphic, photo-oculographic, and magnetoelectro-oculographic methods were used to study and to compare the accuracy of 10 degrees saccadic movements of the eyes in dependence on their direction to the right, to the left, upwards and downwards. Leftward saccades in right-handers and rightward saccades in left-handers proved to be more accurate compared to saccades in the opposite direction. This finding may be related to the functional asymmetry of the cerebral hemispheres. Downward saccades are inaccurate in comparison to upward saccades. Their inaccuracy is caused by overshooting the target. In the case of vertical saccades, the existence of different generators in the brain for triggering upward and downward saccades may play a role, along with a potential preprogramming of the change in the downward look into a sequence of two saccades. The obtained results emphasize the requirement of calibrating the electro-oculogram by saccades in that direction in which the analyzed eye movements are recorded.

Adult↗
PubMed1997

The relationship between curvature and velocity in two-dimensional smooth pursuit eye movements.

Curvature and tangential velocity of voluntary hand movements are constrained by an empirical relation known as the Two-Thirds Power Law. It has been argued that the law reflects the working of central control mechanisms, but it is not known whether these mechanisms are specific to the hand or shared also by other types of movement. Three experiments tested whether the power law applies to the smooth pursuit movements of the eye, which are controlled by distinct neural motor structures and a peculiar set of muscles. The first experiment showed that smooth pursuit of elliptic targets with various curvature-velocity relationships was most accurate when targets were compatible with the Two-Thirds Power Law. Tracking errors in all other cases reflected the fact that, irrespective of target kinematics, eye movements tended to comply with the law. Using only compatible targets, the second experiment demonstrated that kinematics per se cannot account for the pattern of pursuit errors. The third experiment showed that two-dimensional performance cannot be fully predicted on the basis of the performance observed when the horizontal and vertical components of the targets used in the first condition were tracked separately. We conclude that the Two-Thirds Power Law, in its various manifestations, reflects neural mechanisms common to otherwise distinct control modules.

Adult↗
PubMed1977

Gaze failure, drifting eye movements, and centripetal nystagmus in cerebellar disease.

Three abnormalities of eye movement in man are described which are indicative of cerebellar system disorder, namely, centripetally beating nystagmus, failure to maintain lateral gaze either in darkness or with eye closure, and slow drifting movements of the eyes in the absence of fixation. Similar eye movement signs follow cerebellectomy in the primate and the cat. These abnormalities of eye movement, together with other signs of cerebellar disease, such as rebound alternating, and gaze paretic nystagmus, are explained by the hypothesis that the cerebellum helps to maintain lateral gaze and that brain stem mechanisms which monitor gaze position generate compensatory biases in the absence of normal cerebellar function.

Adult↗
PubMed1994

Abnormal eye movements in blepharospasm and involuntary levator palpebrae inhibition. Clinical and pathophysiological considerations.

We report on four patients with involuntary eyelid closure and eye movement disorders. Three were healthy until the onset of their illness and one had a mild generalized choreoathetosis and dystonia due to kernicterus. Electromyographic recording revealed solely blepharospasm in two patients and blepharospasm in combination with involuntary levator palpebrae inhibition in the other two. The eye movement abnormalities were clinically characterized by inability to fix gaze and short or prolonged episodes of uncontrollable eye deviations accompanied, in two patients, by diplopia in horizontal or vertical directions. These episodes occurred independently of a disorder of eyelid movement. Eye movement recordings with a double magnetic induction technique showed saccadic intrusions in horizontal directions. They consisted of highly frequent square wave jerks in three and sporadic macro-square wave jerks in two patients. There were also episodes of extraocular muscle dystonia, commonly known as oculogyric crises, resulting in involuntary upward eye deviation in all patients and lateral deviation in three patients. In one patient, nasal-ward deviations were sometimes restricted to one eye. We conclude that these abnormal eye movements do not necessarily point to a symptomatic form of dystonia and that they may limit the beneficial effect of botulinum toxin or surgical intervention in the therapeutic management of involuntary eyelid closure. We suggest that either basal ganglia, especially substantia nigra pars reticularis and the brainstem structures, especially the paramedian pontine reticular formation, or both, may be involved in the pathogenesis of these abnormal movements.

Adult↗