Horizontal Saccadic Eye Movements Research Articles

Oculomotor function during space flight and susceptibility to space motion sickness

Horizontal vestibulo-ocular reflex (VOR) and saccadic eye movements (SEM) were studied in 18 subjects before and during five Space Shuttle missions to evaluate the effects of weightlessness and correlations between results and susceptibility to and actual presence of space motion sickness (SMS). Active sinusoidal head oscillation was the stimulus for VOR tests with vision (VVOR), with eyes shaded (VOR-ES), and VOR suppression (VOR-S). Eye movements were recorded by electrooculography and head position by a potentiometer. No pathological nystagmus or other abnormal eye movements were seen. No significant in-flight changes were seen in the gain, phase shift or waveform of VVOR, VOR-ES or VOR-S. Statistically significant increases in saccadic latency and decreases in saccadic velocity were seen, with no change in saccadic accuracy. Preflight differences between SMS susceptible and non-susceptible subjects were noted only in VOR-S, with less complete suppression in susceptible subjects, a finding also seen in flight. During flight, VVOR gain was significantly increased in three non-affected subjects. Saccades of SMS-affected subjects showed increased latency and velocity and decreased accuracy compared to saccades of unaffected subjects.

Das okulomotorische System — Simulation von physiologischen und pathologischen horizontalen sakkadischen Augenbewegungen - The Oculomotor System - Simulation of Physiological and Pathological Horizontal Saccadic Eye Movements

Horizontal saccadic eye movements were analyzed by way of the input- and output-functions of the oculomotor system. On the basis of the parameters of the model, it was possible to simulate both physiological and pathological saccades. In this paper we present the results of simulation experiments that were performed to study the influence of various ocular motor disorders. The parameters of the model proved a useful diagnostic aid.

Eye movement-related neurons in the red nucleus

Extracellular unit activity of the parvocellular red nucleus (RN) and spontaneous horizontal eye movements were recorded in adult, nitrous oxide-anesthetized and C 1 transected cats. It was found that 7.5% of the neurons of each RN were related to spontaneous horizontal saccadic eye movements. Three types of neurons were observed: (1) bidirectional neurons which increased their frequency of discharge in relation to any horizontal eye movement; (2) unidirectional neurons which altered their frequency of discharge in relation to a horizontal eye movement of a precise direction; and (3) neurons which increased their frequency of discharge in relation to the rapid phase of an horizontal nystagmus. These 3 types of neurons modified their frequency of discharge before the initiation of the eye movement. One pair of oculomotor neurons recorded simultaneously in both RN showed a significant correlation coefficient. These results suggest that the RN may contribute to the preparation or execution of horizontal eye movements.

The influence of saccade length on the saccadic suppression of displacement detection

The decrease in sensitivity to spatial displacement which accompanies a voluntary horizontal saccadic eye movement was measured as a function of the length of the saccade. Threshold for detecting the displacement increased linearly from about 0.3 degrees to 1.2 degrees as saccade length increased from 4 degrees to 12 degrees. The variability (standard deviation) of the discrimination increased linearly with saccade length as well, and hence also linearly with the displacement threshold. These results, along with our previous finding that the increase is not a consequence of the saccadically generated spatiotemporal smearing of the retinal image (Li & Matin, 1990), support the proposal that displacement detection is based on a constant internal signal/noise ratio whose denominator is a measure of the variability of the extraretinal signal regarding eye position, and that the reduction in sensitivity is a result of a transient increase of this variability in the temporal neighborhood of a saccade.

Premotor negativity associated with saccadic eye movement and finger movement: a comparative study

The topography and time course of the premotor negativity (PMN) associated with horizontal saccadic eye movement and with thumb movement has been compared in a group of normal subjects. It was found that the time of onset, slope and distribution of the PMN was essentially the same for both types of movement. This finding suggests that the PMN may reflect primarily a non-movement-specific increase in attention or arousal processes common to both types of movement rather than activity in specific cortical areas concerned with the programming and execution of the movements.

Anatomical evidence of the projection of pontine omnipause neurons to midbrain regions controlling vertical eye movements

Both anatomical and physiological studies have shown that pause neurons (PNs) in the medial pontine reticular formation project to two groups of burst neurons (BNs) involved in the genesis of horizontal saccadic eye movements: The excitatory burst neurons (EBNs), which lie rostral to the abducens nucleus, and the inhibitory burst neurons (IBNs), which lie caudal to the abducens. This study is concerned with the projection from PNs to a group of vertical BNs in the nucleus of the H field of Forel (H FF) in the caudomedial subthalamus. Three anatomical methods were used to demonstrate this connection. First, intra-axonal horseradish peroxidase (HRP) injection into physiologically identified PN axons demonstrated axonal branching and axonal terminations in and around the H FF. Second, micro-injection of the tracer Phaseolus vulgaris leucoagglutinin (PHA-L) into the pontine PN region labelled terminal axons and boutons in the nucleus of the H FF. Third, extracellular pressure injection of HRP into H FF yielded retrogradely labelled pontine PN neurons. These anatomical results confirmed the termination of PNs in areas controlling rapid vertical eye movements as physiologically demonstrated by Nakao et al.: Exp. Brain Res. 70:632-636, '88). This work points to the major role of pontine PNs in the synchronization of BN activity in rapid eye movements in all directions.

Role of saccadic analysis in the diagnosis of multiple sclerosis in the era of magnetic resonance imaging.

Magnetic resonance imaging (MRI) has recently been recognised as the most sensitive method with which to detect clinically silent lesions in patients affected by multiple sclerosis. Visually guided horizontal saccadic eye movements (SEM) were studied, together with MRI, in 57 multiple sclerosis patients. A very similar sensitivity was found for both MRI (78.2%) and SEM analysis (76.3%). Significant associations between peak saccadic velocity and brain stem signs and between saccadic latency and visual signs were observed.

Vertical and horizontal saccadic eye movements in Parkinson's disease

We report the case of a patient with arteriovenous malformation fed by a posterior ethmoidal artery. The pre-operative amaurotic attacks on the diseased eye subsided after removal of the malformation. Doppler sonographic examination of the peripheral ophthalmic artery showed an inversion of the blood flow direction postoperatively. We describe a concept of an ophthalmic steal syndrome treated in this patient by removal of an arteriovenous malformation.

Binocular co-ordination of human horizontal saccadic eye movements.

1. The binocular co-ordination of human horizontal saccades was analysed for the first time systematically over the full oculomotor range with a precise and accurate scleral sensor coil technique. Effects of amplitude (1.25-80 deg), direction (adduction vs. abduction and centrifugal vs. centripetal) and eccentricity (symmetrical about primary or between primary and secondary positions) were systematically investigated in three subjects). 2. To minimize extraneous effects of stimulus presentation on the programming of saccades, subjects were instructed to voluntarily change their gaze between two continuously visible targets. These were positioned on an iso-vergence locus, and thus contained no stimulus for disjunctive eye movements. 3. Under these conditions the amplitudes of the primary saccades of the two eyes were remarkably accurate; undershooting of the target by about 0.5 deg (independent of amplitude in the range 10-70 deg) was typical. This finding contrasts with the undershooting by about 10% described in the literature as characteristic for other stimulus conditions. 4. Saccadic peak velocities saturated at a mean asymptotic level of 502 +/- 32 (S.D.) deg/s for saccades of 40 deg and larger. The duration was linearly related to amplitude for saccades up to 50 deg; for saccades of larger sizes the duration increased progressively more steeply. Skewness values (acceleration time as a fraction of total saccadic duration) decreased from about 0.45 for saccades up to 10 deg to about 0.20 for saccades of 50 deg and larger. 5. Binocular saccades showed an abduction-adduction asymmetry and were not well yoked dynamically. The saccades of the abducting eye consistently had a larger size, a higher peak velocity, a shorter duration and were more skewed than the concomitant adducting saccades of the fellow eye. As a result, the eyes diverged transiently by as much as 3 deg during horizontal saccades. 6. Saccades also showed a marked centrifugal-centripetal asymmetry. Peak velocities of saccades towards the primary position were about 10% higher than peak velocities of corresponding centrifugal saccades. 7. These directional asymmetries were the main source of variability in the pool of saccades. In comparison, intra- and intersubject variability was minor in our sample. 8. Post-saccadic drift consisted of a vergence and a version component. The vergence component of this drift was a continuation of the vergence movement occurring during saccades. The version component, generally smaller than the vergence component, was directed towards the target position.(ABSTRACT TRUNCATED AT 400 WORDS)

Frequency response analysis of human saccadic eye movements: Estimation of stochastic muscle forces

A frequency response method is used to estimate parameters of a fourth-order model of the oculomotor system and the active state tensions during a saccadic eye movement. The lateral and medial rectus muscle of each eye is modeled as a parallel combination of an active state tension generator with a viscosity and elastic element, connected to a series elastic element. The eyeball is modeled as a sphere connected to a viscosity and elastic element. Each of these elements is assumed to be ideal and linear. The active state tension for each muscle is modeled by a low-pass filtered pulse-step waveform. Initial estimates of the oculomotor mechanical components are based on physiological evidence. Initial estimates of the active state tension are based on an extrapolation of the eye movement trajectory. Horizontal saccadic eye movements were recorded from infrared signals reflected from the anterior surface of the cornea and then digitized. Parameter estimates were calculated for the model by using a conjugate gradient search program which minimizes the integral of the absolute value of the squared error between the model and the data. The predictions of the model are shown to be in good agreement with the data. Final estimates of motoneuronal activity demonstrate that the agonist muscle is maximally stimulated during the early portion of a saccadic eye movement regardless of the amplitude of the saccade; only the duration of the maximal stimulation affects the size of the saccade. The antagonist muscle is completely inhibited during the period of maximum agonist muscle stimulation. Furthermore, it is demonstrated that saccade motoneuronal activity is a stochastic phenomenon.

Time-optimal control of saccadic eye movements.

A new theory describing the time-optimal control of saccadic eye movements is proposed based on Pontryagin's minimum principle and physiological considerations. The lateral and medial rectus muscle of each eye is assumed to be a parallel combination of an active state tension generator with a viscosity and elastic element, connected to a series elastic element. The eyeball is modeled as a sphere connected to a viscosity and elastic element. Each of these elements is assumed to be ideal and linear. The neuronal control strategy is shown to be a first-order time-optimal control signal. Under this condition, the active state tension for each muscle is a low-pass filtered pulse-step waveform. The magnitude of the agonist pulse is a maximum for saccades of all sizes and only the duration of the agonist pulse affects the size of the saccade. The antagonist muscle is completely inhibited during the period of maximum stimulation for the agonist muscle. Horizontal saccadic eye movements were recorded from infrared signals reflected from the anterior surface of the cornea and then digitized. Parameter estimates for the model were calculated by using a conjugate gradient search program which minimizes the integral of the absolute value of the squared error between the model and the data. The predictions of the model under a time-optimal controller are in good agreement with the data.

Onion bulb formations in oculomotor nerves

Four patients with predominantly right-sided infarcts at the midbrain-diencephalic junction had an ipsilateral oculomotor palsy and contralateral gaze palsy. The gaze palsy to the left was supranuclear in nature, because the restriction of abduction was overcome by the oculocephalic reflex. However, it was masked on the right eye by the third nerve palsy. In all cases upgaze was impaired bilaterally, and infraduction was absent on the right. The restriction of abducting saccades remained for months, considerably longer than with supranuclear cortical lesions, suggesting that the damage extended beyond involvement of the frontopontine pathways. These cases represent clinical instances of a recently described experimental syndrome of impaired horizontal saccadic eye movements with lesions at the paramedian midbrain-diencephalic junction.

Lidblink artifacts in recordings of horizontal saccadic eye movements with the infrared reflection method: Analysis and presentation of a new monitoring technique

In order to test the accuracy of lidblink artifact monitoring with EOG during recordings of horizontal saccadic eye movements by means of Infrared Reflection Oculography (IROG), the influences of EOG-recorded blinks of different size on amplitude, peak velocity, and duration of horizontal saccades were studied in ten healthy volunteers. During the study, a simpler blink monitoring technique was developed using IROG itself. in six subjects the conventional ‘retinoelectric’ (EOG) and the new ‘photoelectric’ (IROG) blink artifact monitoring methods were simultaneously employed. A comparison of the two methods showed that photoelectric blink monitoring not only is much simpler to install, but also yields less false positive, as well as less false negative results than retinoelectric monitoring. in addition, photoelectric monitoring gives a continuous control of the placement of the photo cells with respect to the horizontal plane, which is important to avoid asymmetric blink artifacts in the IROG recordings d...

Presaccadic spike potential. Relation to eye movement direction

The spike potential (SP) which precedes horizontal saccadic eye movement has been shown to arise in the agonist lateral and medial rectus muscles of the two eyes. To determine whether other extra-ocular muscles also generate an SP, recordings were carried out in normal subjects performing vertical and oblique as well as horizontal saccades. An SP was recorded before saccades in all directions. The potential was highest in amplitude with horizontal or oblique abducting saccades and was higher in amplitude with vertical upgoing than downgoing saccades.

Horizontal and vertical saccadic eye movement abnormalities in Huntington's chorea

With a newly developed infrared reflection technique, voluntary saccadic eye movements (VOLS), visually evoked saccades (VES) and unsuppressed visually evoked reflex saccades (USVERS) were measured in 11 patients with Huntington's chorea. Abnormalities, including latency increase, peak velocity decrease and undershoot dysmetria with multiple step saccades were found in all types of saccadic eye movements. Peak velocity decrease and undershoot dysmetria can be explained by dysfunction of the brainstem reticular formation in Huntington's chorea. USVERS and square wave jerks occurred abnormally frequently and showed direction-dependent differences. Both were more frequent in horizontal than in vertical direction. Frequency of USVERS and square-wave jerks tended to be correlated. These findings point to disinhibited superior colliculi as a possible common supranuclear origin of USVERS and square-wave jerks in Huntington's chorea.

Recording of Horizontal Saccadic Eye Movements: Methodological Comparison Between Electro-Oculography and Infrared Reflection Oculography

Simultaneous recordings with monocular direct current electro-oculography (EOG) and infrared reflection oculography (IROG) from the same eye were performed to investigate methodological differences. In six healthy volunteers 20 and 30 degree midline crossing horizontal saccades were recorded using different low bandpass filtering and two different temporal EOG electrode placements. Important dissimilarities with regard to peak velocity and saccade duration were found between the two recording techniques. The most striking difference was encountered in the abducting (temporal) saccades, where EOG measured significantly slower velocities and, in most instances, longer durations of the saccades. As a consequence, EOG usually measured faster adducting and IROG faster abducting saccades. This discrepancy was further demonstrated in two additional control groups of healthy individuals with the two methods used separately. The authors conclude that the IROG more faithfully reflects rapid eye movements within the...

Speed-accuracy characteristics of saccadic eye movements.

Speed-accuracy trade-off characteristic of horizontal saccadic eye movements were examined in this study. Unlike limb movements, saccadic eye movements are preprogrammed, unidimensional, and do not involve target impact. Hence, they provide an optimal test of the impulse variability account of the speed-accuracy trade-off in rapid movements. Subjects were required to alternately look at two target lights as fast and as accurately as possible for a period of 10 s. Target lights subtended angles of 5, 10, 15, and 20 degrees. By restricting target distances to less than 20 degrees of arc, the speed-accuracy relation was examined for single horizontal saccadic movements of the eye. movement of the dominant eye was tracked with an infra-red eye monitoring device. Fifty saccadic movements of the eye were recorded for each target distance and used to compute the average amplitude, duration, and velocity of eye movements, as well as, movement endpoint variability. An increase in both average velocity and movement endpoint variability with increasing movement amplitude was found. This, together with the unique features of the eye movement system, support the impulse variability account of the speed-accuracy trade-off in rapid movements.

Eye movements in patients with absent voluntary horizontal gaze

Despite the complete absence of horizontal saccades, two patients with pontine gliomas had horizontal reflex eye movements within a range of +/- 20 degrees. The gain (peak eye velocity/peak stimulus velocity) and phase of the vestibulo-ocular reflex were normal, but the optokinetic gain was decreased. The latency, accuracy, and peak velocity of vertical saccades were normal. Apparently the voluntary gaze centers in the pontine reticular formation are not crucial for generating horizontal vestibular or vertical saccadic eye movements.

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Six healthy young adults were selected to examine the influence of blindfolding one eye on the production of horizontal saccadic eye movements under a monocular lead. A saccade-evoking apparatus (Nagashima K-N 50) was used to induce random saccades. Standard electronystagmography with a time constant of 3.0 and a paper speed of 50 mm/sec was emplo. yed for the recording of eye movements. Two main characteristic findings were obtained with both eyes open: the volocity of the saccades increased in proportion as the amplitude of the saccade rose, and the velocity of adduction was significantly faster than that of abduction.Under unilateral blindfolding, the saccades towards the blindfolded eye showed no difference of velocity between adduction and abduction and no significantly increased velocity although the amplitude increased. However no significant change was noted in saccades towards the non-blindfolded eye. The neural pathways responsible for this finding are considered.

Saccadic eye movement analysis as a measure of drug effects on human psychomotor performance.

Analysis of human horizontal saccadic eye movements can provide measurements of central nervous system depression and stimulation. Effects on saccadic eye movements have been observed in normal volunteers with barbiturates, benzodiazepines, opiates and related compounds, carbamazepine, amphetamine and ethanol. A suite of programmes have been developed to allow the generation, collection and analysis of saccadic eye movements using a CBM 3032, 8032 or BBC B microcomputer. The system allows almost continuous sampling and rapid analysis of movements.