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While awake, unanesthetized monkeys held their eyes stationary, a motionless or slowly moving stimulus falling on the receptive field of striate cortex neurons produced an excitatory response. When a rapid eye movement was made across the same stimulus, many of these neurons continued to give an excitatory response. But the discharge of other neurons was unchanged or was suppressed during the eye movement.
We studied abnormalities of eye movement in five patients with Arnold-Chiari malformation before and after suboccipital decompression. Before operation all patients complained of oscillopsia at rest and visual blurring of fixated targets during and immediately after their heads were in motion. Three patients had downbeat nystagmus, one patient had horizontal nystagmus in the primary position and on eccentric gaze and one patient had rotatory nystagmus on lateral gaze only. Smooth pursuit, optokinetic nystagmus and fixation suppression of vestibular nystagmus were markedly impaired. Within two months after operation nystagmus in the primary position had resolved in three patients, and four had complete to near-complete resolution of nystagmus in all gaze positions over subsequent months. Oscillopsia decreased concurrently. affording significant functional visual improvement. One patient had only slight functional improvement and continued to have prominent nystagmus seven years after operation. Smooth pursuit, optokinetic nystagmus and fixation suppression of vestibular nystagmus improved in all patients, but none had complete recovery at the higher velocities of stimulation. They still complained of visual blurring associated with head motion, probably due to the poor fixation suppression of vestibular nystagmus. Our findings suggest that abnormalities of eye movement in Arnold-Chiari malformation are due to compression of the herniating cerebellum against the caudal brain-stem and not a congenital aberrancy of oculomotor pathways. Nystagmus resolved more readily than pursuit or fixation suppression abnormalities, but most patients showed gradual improvement in all abnormalities four months after operation.
We examined the influence of a peripheral visual stimulus on eye movement while monkeys performed a horizontal step-ramp pursuit task. When an irrelevant visual stimulus was presented before the onset of the target motion, slow eye movement away from the stimulus was observed. When the stimulus appeared during a temporal gap between the offset of the fixation point and the onset of target motion the velocity of the slow eye movement increased. The onset of the movement was time-locked to the onset of the extraneous visual stimulus and its latency was comparable to the latency of smooth pursuit in trials without a peripheral stimulus. The results demonstrate a new form of smooth eye movement, suggesting that the eye movement may be contained in the initial stages of smooth pursuit observed in step-ramp paradigms.
An automated method for detecting and counting eye movements using the electrooculogram (EOG) wave form during rapid-eye-movement (REM) sleep is presented. The method is formulated as a sequential decision process with decisions based on slope and amplitude threshold criteria. Signal processing techniques such as digital filtering and smoothing are used to improve the effectiveness of the method. Validation is done by using the method on EOG data from three infants and comparing the automated count of eye movements with the visual counts of human observers. The correlation coefficient between the automated and visual count is greater than 0.9, the first-order regression coefficient close to 1.0, and the zero-order regression coefficient close to 0. We believe that this method will be useful in differentiating between the substates of REM sleep in studies of cardiorespiratory physiology.
The time curve of the electrooculogram (EOG) as applied to clinical diagnosis is measured as the changes in the standing potentials around the eyes when a subject performs saccadic eye movements of constant amplitude. If the characteristics of these potential changes caused by the eye movements are known, the time curves of EOG can be derived from the potential changes generated by saccadic eye movements of random amplitude, by transforming the measured potentials into the exact values corresponding to the constant amplitudes of saccades. We have already reported that the characteristic curves of EOG are proportional to the angles of the eye movements within +/- 20. However, Fenn and Hursh reported that the characteristics of saccadic eye movements for larger amplitudes up to about 80 degrees were sinusoidal functions. Other workers have reported linear relations of the characteristics of EOG. In this report we attempted to clarify whether the characteristics of EOG were linear or sinusoidal. From our experiments it became clear that the characteristics of EOG could be approximated to straight lines up to about 80 degrees (visual angle).
Single cell responses were recorded from the superior colliculus of awake monkeys trained to move their eyes. A class of cells that discharged before eye movements was found in the intermediate and deep layers of the colliculus. The response of the cells was most vigorous before saccadic eye movements within a particular range of directions. These cells had no visual receptive fields, and visually guided eye movements were not necessary for their discharge, since they responded in total darkness before spontaneous eye movements and vestibular nystagmus.
The present study obtained saccadic eye movements from 25 right-handed normal subjects (aged 18-35 yr, mean 22.4 yr) to examine the effects of saccade direction on saccadic parameters (latency, duration and average velocity). Binocular saccadic eye movements were recorded with a direct-current electrooculographic system, and analysis was performed on a laboratory digital computer. The LED target positions were randomly selected 10, 15, 20, 25 and 30 degrees to the left or right of the fixation points. In general, the mean values of the saccadic parameters over large saccade angles were in agreement with those previously reported. There were no significant differences between saccades directed to the right and to the left.
Cognitive processes are accompanied by eye movements, which are interrupted by fixations of an almost infinite number of points in the visual field. To investigate these processes, a systematic analysis of those movements is required to structure the long sequences of fixations. This task is possible if there are interrelationships between the ongoing thought processes and the fixations. Such interrelationships may manifest themselves through certain patterns of eye movements. It often happens that subsets of visual points are being looked at repeatedly. This is because a cognitive connection among the subset's elements is being discovered or created by such repetition. The method presented here attempts to achieve automatic recognition of fixation point patterns. Its usefulness is demonstrated using data from an experiment where eye movements were recorded while subjects were solving Raven Test items. The method may be characterized as a variant of time series analysis for nominal data. It is suitable for non-numerical data in general.
The paper addresses distinctions between hypnotic interventions and Eye Movement Desensitizing and Reprocessing (EMDR) and discusses their effect on persons who have symptoms of Posttraumatic Stress Disorder (PTSD). Eye movements in hypnosis and EMDR are considered in terms of the different ways they may affect responses in treatment. A treatment intervention within hypnosis called ECEM (Eye Closure, Eye Movements) is described. ECEM can be used for patients with histories of trauma who did not benefit adequately from either interventions in hypnosis or the EMDR treatment protocol used separately. In ECEM the eye movement variable of EMDR is integrated within a hypnosis protocol to enhance benefits of hypnosis and reduce certain risks of EMDR.
Vergence eye movements were elicited in human subjects by applying disparities to square-wave gratings lacking the fundamental ("missing fundamental", mf). Using a dichoptic arrangement, subjects viewed gratings that were identical at the two eyes except for a phase difference of 1/4 wavelength so that, based on the nearest-neighbor matches, the features and the 4n+1 harmonics (5th, 9th, etc.) all had binocular disparities of one sign, whereas the 4n-1 harmonics (3rd, 7th, etc.) all had disparities of the opposite sign. Further, the amplitude of the ith harmonic was proportional to 1/i. Using the electromagnetic search coil technique to record the positions of both eyes indicated that the earliest vergence eye movements elicited by these disparity stimuli had ultra-short latencies (minimum, <65 ms) and were always in the direction of the most prominent harmonic, the 3rd, but their magnitudes fell short of those elicited when the same disparities were applied to pure sinusoids whose spatial frequency and contrast matched those of the 3rd harmonic. This shortfall was evident in both the horizontal vergence responses recorded with vertical grating stimuli and the vertical vergence responses recorded with horizontal grating stimuli. When the next most prominent harmonic, the 5th, was removed from the mf stimulus (creating the "mf-5" stimulus) the vertical vergence responses showed almost no shortfall-indicating that it had been almost entirely due to that 5th harmonic-but the horizontal vergence responses still showed a small shortfall, at least with higher contrast stimuli. This small shortfall might represent a very minor contribution from higher harmonics and/or distortion products and/or a feature-based mechanism. We conclude that the earliest disparity vergence responses-especially vertical-were strongly dependent on the major Fourier components of the binocular images, consistent with early spatial filtering of the monocular visual inputs prior to their binocular combination as in the disparity-energy model of complex cells in striate cortex [Ohzawa, I., DeAngelis, G. C., & Freeman, R. D. (1990). Stereoscopic depth discrimination in the visual cortex: neurons ideally suited as disparity detectors. Science, 249, 1037-1041].
The recording and analysis of eye movements are fundamental to a diverse set of research applications, including studies in which reading, visual search, and both overt and covert visuospatial attention are examined. Software tools supplied with commonly available eye-tracking equipment have generally been limited in functionality and nonextensible. Because of this dearth of available software, ELAB was created to provide an extensible framework for analyzing various aspects of eye movements. The program consists of a series of open-source MATLAB functions. The program's data structures keep raw data, analysis preferences, and analyzed data separate, thus maintaining data fidelity and promoting extensibility.
The present study was conducted to determine whether the usual temporal relationship between rapid eye movement and penile tumescence was present in a group of narcoleptic patients who had demonstrated the abnormal phenomenon of sleep onset rapid eye movement. We studied 5 men with a clinical history of sleep attacks and at least 1 auxiliary symptom of narcolepsy. Results indicated that penile tumescence occurred during temporally normal and abnormal rapid eye movement sleep. These findings provide further evidence of the strong temporal relationship between rapid eye movement sleep and penile tumescence.
The vestibulocerebellum is involved in the control of compensatory eye movements. To investigate its role in learning and timing of motor behavior, we investigated compensatory eye movements in mice with the use of search coils. Wild-type mice showed the ability to increase the gain of their vestibulo-ocular reflex by visuovestibular training. This adaptation did not occur in lurcher mice, a natural mouse mutant that completely lacks Purkinje cells. During the optokinetic reflex the phase of the eye movements of lurcher mice in reference to the stimulus lagged behind that of wild-type littermates, whereas during the vestibulo-ocular reflex it led that of the wild-type mice. During combined optokinetic and vestibular stimulation, the phase of the lurcher mice lagged behind that of the wild-type mice at the low stimulus frequencies, whereas it led the phase of the wild-type mice at the high frequencies. In addition, the optokinetic response of the lurcher mice showed a significantly longer latency during constant-velocity step stimulation than that of the wild-type mice. We conclude that Purkinje cells are necessary for both learning and timing of compensatory eye movements in mice. The present description of gain adaptation and phase dynamics provides the basis for studies in which the molecular mechanisms of cerebellar control of compensatory eye movements are investigated with the use of genetically manipulated mice.
The aminergic neurons in the locus coeruleus are known to cease firing during rapid eye movement sleep. Since electrical stimulation of locus coeruleus reduced, while carbachol stimulation increased rapid eye movement sleep and gamma-aminobutyric acid (GABA) neurons as well as terminals are present in the locus coeruleus, we hypothesized that GABA may be involved for cessation of locus coeruleus neuronal firing during rapid eye movement sleep. Under surgical anaesthesia male Wistar rats (250-300 g) with bilateral guide cannulae targeting locus coeruleus were prepared for chronic sleep-wakefulness recording. Electroencephalogram (EEG), electrooculogram (EOG), electromyogram (EMG) were recorded in normal, after 250 nl saline and after picrotoxin (250 ng in 250 nl) injection bilaterally into the locus coeruleus. The results showed that mean duration per episode of rapid eye movement sleep was significantly reduced, although its frequency of generation/h was not significantly affected. This study suggests that GABA in locus coeruleus is involved in tonic regulation of rapid eye movement sleep and the action is mediated through GABAA receptor.
Anatomical studies in goldfish show that the tectofugal axons provide a large number of boutons within the mesencephalic reticular formation. Electrical stimulation, reversible inactivation and cell recording in the primate central mesencephalic reticular formation have suggested that it participates in the control of rapid eye movements (saccades). Moreover, the role of this tecto-recipient area in the generation of saccadic eye movements in fish is unknown. In this study we show that the electrical microstimulation of the mesencephalic reticular formation of goldfish evoked short latency saccadic eye movements in any direction (contraversive or ipsiversive, upward or downward). Movements of the eyes were usually disjunctive. Based on the location of the sites from which eye movements were evoked and the preferred saccade direction, eye movements were divided into different groups: pure vertical saccades were mainly elicited from the rostral mesencephalic reticular formation, while oblique and pure horizontal were largely evoked from middle and caudal mesencephalic reticular formation zones. The direction and amplitude of pure vertical and horizontal saccades were unaffected by initial eye position. However the amplitude, but not the direction of most oblique saccades was systematically modified by initial eye position. At the same time, the amplitude of elicited saccades did not vary in any consistent manner along either the anteroposterior, dorsoventral or mediolateral axes (i.e. there was no topographic organization of the mesencephalic reticular formation with respect to amplitude). In addition to these groups of movements, we found convergent and goal-directed saccades evoked primarily from the anterior and posterior mesencephalic reticular formation, respectively. Finally, the metric and kinetic characteristics of saccades could be manipulated by changes in the stimulation parameters. We conclude that the mesencephalic reticular formation in goldfish shares physiological functions that correspond closely with those found in mammals.
The mechanics of the eyeball and its surrounding tissues, which together form the oculomotor plant, have been shown to be the same for smooth pursuit and saccadic eye movements. Hence it was postulated that similar signals would be carried by motoneurons during slow and rapid eye movements. In the present study, we directly addressed this proposal by determining which eye movement-based models best describe the discharge dynamics of primate abducens neurons during a variety of eye movement behaviors. We first characterized abducens neuron spike trains, as has been classically done, during fixation and sinusoidal smooth pursuit. We then systematically analyzed the discharge dynamics of abducens neurons during and following saccades, during step-ramp pursuit and during high velocity slow-phase vestibular nystagmus. We found that the commonly utilized first-order description of abducens neuron firing rates (FR = b + kE + r, where FR is firing rate, E and are eye position and velocity, respectively, and b, k, and r are constants) provided an adequate model of neuronal activity during saccades, smooth pursuit, and slow phase vestibular nystagmus. However, the use of a second-order model, which included an exponentially decaying term or "slide" (FR = b + kE + r + uE - c), notably improved our ability to describe neuronal activity when the eye was moving and also enabled us to model abducens neuron discharges during the postsaccadic interval. We also found that, for a given model, a single set of parameters could not be used to describe neuronal firing rates during both slow and rapid eye movements. Specifically, the eye velocity and position coefficients (r and k in the above models, respectively) consistently decreased as a function of the mean (and peak) eye velocity that was generated. In contrast, the bias (b, firing rate when looking straight ahead) invariably increased with eye velocity. Although these trends are likely to reflect, in part, nonlinearities that are intrinsic to the extraocular muscles, we propose that these results can also be explained by considering the time-varying resistance to movement that is generated by the antagonist muscle. We conclude that to create realistic and meaningful models of the neural control of horizontal eye movements, it is essential to consider the activation of the antagonist, as well as agonist motoneuron pools.
We studied the strategic (presumably cortical) control of ocular fixation in experiments that measured the fixation offset effect (FOE) while manipulating readiness to make reflexive or voluntary eye movements. The visual grasp reflex, which generates reflexive saccades to peripheral visual signals, reflects an opponent process in the superior colliculus (SC) between fixation cells at the rostral pole, whose activity helps maintain ocular position and increases when a stimulus is present at fixation, and movement cells, which generate saccades and are inhibited by rostral fixation neurons. Voluntary eye movements are controlled by movement and fixation cells in the frontal eye field (FEF). The FOE--a decrease in saccade latency when the fixation stimulus is extinguished--has been shown to reflect activity in the collicular eye movement circuitry and also to have an activity correlate in the FEF. Our manipulation of preparatory set to make reflexive or voluntary eye movements showed that when reflexive saccades were frequent and voluntary saccades were infrequent, the FOE was attenuated only for reflexive saccades. When voluntary saccades were frequent and reflexive saccades were infrequent, the FOE was attenuated only for voluntary saccades. We conclude that cortical processes related to task strategy are able to decrease fixation neuron activity even in the presence of a fixation stimulus, resulting in a smaller FOE. The dissociation in the effects of a fixation stimulus on reflexive and voluntary saccade latencies under the same strategic set suggests that the FOEs for these two types of eye movements may reflect a change in cellular activity in different neural structures, perhaps in the SC for reflexive saccades and in the FEF for voluntary saccades.
The relationship between rapid-eye-movement (REM) sleep tonic and phasic activity measures and the pre- and postprobenecid cerebrospinal fluid (CSF) concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) was examined in a sample of 14 unmedicated psychiatric patients. The average duration of an eye movement burst and the average number of eye movements within a burst were found to be inversely related to the probenecid corrected accumulation of 5-HIAA in the CSF. These results are interpreted as indicating an association between REM burst eye movement activity and serotonin turnover in psychiatric subjects.