The movement after-effect and eye movements.
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Eye Movements↗
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Development of responses by facial expressions and eye movements in neonates and young infants.
Eye movements and facial expressions were assessed in 177 normal neonates and infants under 150 days of age after the examiner gazed into their eyes for 20 seconds. Blinking to a threatening stimulus and turning of the eyes towards a red object near the examiner's face were tested. The eye movements abruptly changed from fine nystagmoid movements to distinct rolling movements suggesting observation of the examiner's face after 70-80 days of age. Rapid turning of the eyes towards the red object also appeared from the same age, while blinking developed gradually after 40 days of age. Most infants under 80-90 days of age knitted their brows and showed esophoria in response to the examiner's face or facial movements, but such responses gradually disappeared after 90 days of age when social smiles developed. Eye movements and facial expressions during early infancy are very informative in developmental evaluations.
Blinking↗
Alpha asymmetry as a function of cognitive mode: the role of lateral eye movements.
When monitored concurrently, the spontaneous lateral eye movements and alpha asymmetry associated with mental activity were themselves interrelated. Left eye movements were associated with a decrease in the ratio of right to left hemisphere alpha, while right eye movements resulted in an increase in this ratio, independent of cognitive task. The results were interpreted as evidence for a direct effect of oculomotor activity on alpha asymmetry.
Adult↗
Neural pathways common to vestibular and optokinetic eye movements.
To determine how vestibular and optokinetic eye movement signals share the central oculomotor neural organization, optokinetic afternystagmus was superposed on vestibular nystagmus in the monkey. To a first approximation there was algebraic additivity in the velocity domain. This result suggests that vestibular and optokinetic eye movements are integrated at a level of neural organization above the ocular motoneurons, at a level in which neural signals are coded in terms of eye movement velocity rather than eye position.
Animals↗
Differences in cerebral activation during smooth pursuit and saccadic eye movements using positron-emission tomography.
BACKGROUND: Abnormalities of smooth pursuit eye movements occur commonly in schizophrenia, but the pathophysiological significance of these abnormalities is unknown. To address this, the authors conducted a pilot study in which we examined differences in regional cerebral activation using positron-emission tomography (PET) in normal volunteers as they performed two types of eye movements. METHODS: Cerebral activation in 10 normal volunteers was studied using C15O2 PET while subjects tracked a visual target using smooth pursuit and saccadic eye movements. A left-hand movement comparison task provided a physiologic landmark for verification of the location of the frontal eye fields (FEFs). RESULTS: Subjects exhibited FEF activation during both smooth pursuit and saccadic eye movements, which was greater in the latter. During smooth pursuit, subjects also exhibited increased cerebral activation in the left temporal-occipital border and left superior frontal cortex and decreased activation in medial superior parietal and insular regions relative to saccades. Other cortical visual and eye-movement brain regions also demonstrated differences in activation between the two visual tasks. CONCLUSIONS: Significant fEF activation appears to underlie both smooth pursuit and saccadic eye movements but may be more critical in the former. Dysfunction of the frontal lobe, and possibly of other areas in the pursuit pathway such as the temporo-occipital motion area, may contribute to observed eye-movement abnormalities in patients with schizophrenia.
Adolescent↗
Quantitative differences in smooth pursuit and saccadic eye movements.
Recently it has been suggested that smooth pursuit (SP) and saccadic (SAC) eye movements share many common brain substrates in the planning and control of eye movements (Krauzlis in J Neurophysiol 91:591-603, 2004). Evidence is mounting that these two types of eye movements may also share similar mechanisms used to drive both reactive and predictive eye movement responses (Missal and Keller in J Neurophysiol 88:1880-1892, 2002, Keller and Missal in Ann NY Acad Sci 1004:29-39, 2003). The objective of this study was to quantify these similarities by establishing whether the behavioural response properties of human eye movements to predictive (PRD) and randomized (RND) conditions are quantitatively similar for both SP and SAC in directly comparable paradigms. Two previous studies have attempted to evaluate the coordination and motor preparation time of SP and saccadic eye movements (Erkelens in Vis Res 46:163-170, 2006; Joiner and Shelhamer in Exp Brain Res, Epub ahead of print, 2006). However, no previous study has quantitatively evaluated PRD and RND conditions to discretely presented SP and SAC tasks. We used simple SAC and SP paradigms in blocks of PRD and RND presentations, with eye movements monitored throughout using an IR-limbus eye-tracking system (Skalar). Twelve normal subjects (aged between 20 and 39 years) participated in the study which took place over two recording sessions, on two separate days. Data were analysed for two main comparable descriptive statistics: latency and eye velocity/displacement gain. The results presented here support the notion that SP and SAC share common brain substrates/mechanisms in the generation of responses to PRD and RND visual targets but differ in the movement preparation time.
Adult↗
Development of an eye-movement analyser possessing functions for wireless transmission and autocalibration.
An eye pointer was developed as a new line-of-sight displacement analyser. It analyses an observer's eye movements and superimposes their line of vision on a TV image which is the same as their view. A newly developed miniature colour field camera and very compact eye-movement sensors are attached to a translucent reinforced plastic goggle affording a wide view and excellent safety. A small case is provided for the eye-movement detecting circuit and the camera controller unit etc. Its weight is only 1.2 kg and one can easily participate in sports activities while wearing it. Eye-movement data are transmitted with the VHF video signal. The receiver, which analyses the eye movements and processes the TV image, is also compact and easy to carry. The calibration is automatic and completed within 1 min with a high degree of accuracy. By showing the tennis player's line of vision as an example, we were able to obtain good results with application in broadcasting programmes.
Eye Movements↗
Intentionally-evoked modulations of smooth pursuit eye movements.
When observers pursue a moving target with their eyes, they use predictions of future target positions in order to keep the target within the fovea. It was suggested that these predictions of smooth pursuit (SP) eye movements are computed only from the visual feedback of the target characteristics. As a consequence, if the target vanishes unexpectedly, the eye movements do not stop immediately, but they overshoot the vanishing point. We compared the spatial and temporal features of such predictive eye movements in a task with or without intentional control over the target vanishing point. If the observers stopped the target with a button press, the overshoot of the eyes was reduced compared to a condition where the offset was computer generated. Accordingly, the eyes started to decelerate well before the target offset and lagged further behind the target when it disappeared. The involvement of intentionally-generated expectancies in eye movement control was also obvious in the spatial trajectories of the eyes, which showed a clear flexion in anticipation of the circular motion path we used. These findings are discussed together with neurophysiological mechanisms underlying the SP eye movements.
Acceleration↗
Discharge patterns in nucleus prepositus hypoglossi and adjacent medial vestibular nucleus during horizontal eye movement in behaving macaques.
1. Monkeys were trained to perform a variety of horizontal eye tracking tasks designed to reveal possible eye movement and vestibular sensitivities of neurons in the medulla. To test eye movement sensitivity, we required stationary monkeys to track a small spot that moved horizontally. To test vestibular sensitivity, we rotated the monkeys about a vertical axis and required them to fixate a target rotating with them to suppress the vestibuloocular reflex (VOR). 2. All of the 100 units described in our study were recorded from regions of the medulla that were prominently labeled after injections of horseradish peroxidase into the abducens nucleus. These regions include the nucleus prepositus hypoglossi (NPH), the medial vestibular nucleus (MVN), and their common border (the "marginal zone"). We report here the activities of three different types of neurons recorded in these regions. 3. Two types responded only during eye movements per se. Their firing rates increased with eye position; 86% had ipsilateral "on" directions. Almost three quarters (73%) of these medullary neurons exhibited a burst-tonic discharge pattern that is qualitatively similar to that of abducens motoneurons. There were, however, quantitative differences in that these medullary burst-position neurons were less sensitive to eye position than were abducens motoneurons and often did not pause completely for saccades in the off direction. The burst of medullary burst position neurons preceded the saccade by an average of 7.6 +/- 1.7 (SD) ms and, on average, lasted the duration of the saccade. The number of spikes in the burst was well correlated with saccade size. The second type of eye movement neuron displayed either no discernible burst or an inconsistent one for on-direction saccades and will be referred to as medullary position neurons. Neither the burst-position nor the position neurons responded when the animals suppressed the VOR; hence, they displayed no vestibular sensitivity. 4. The third type of neuron was sensitive to both eye movement and vestibular stimulation. These neurons increased their firing rates during horizontal head rotation and smooth pursuit eye movements in the same direction; most (76%) preferred ipsilateral head and eye movements. Their firing rates were approximately in phase with eye velocity during sinusoidal smooth pursuit and with head velocity during VOR suppression; on average, their eye velocity sensitivity was 50% greater than their vestibular sensitivity. Sixty percent of these eye/head velocity cells were also sensitive to eye position. 5. The NPH/MVN region contains many neurons that could provide an eye position signal to abducens neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Neurobiology of smooth pursuit eye movement deficits in schizophrenia: an fMRI study.
OBJECTIVE: Smooth pursuit eye movements are abnormal in patients with schizophrenia. The investigators used functional magnetic resonance imaging (fMRI) to compare brain hemodynamic response during a smooth pursuit eye movement task in patients with schizophrenia and healthy comparison subjects. METHOD: Fourteen patients with schizophrenia and 14 healthy comparison subjects performed a smooth pursuit eye movement task while undergoing 1.5-T fMRI. Echo-planar images from the blocked design were evaluated with both a whole-brain random-effects analysis and a region-of-interest analysis. Smooth pursuit deficits were assessed outside the fMRI apparatus by using infrared oculography and were assessed during scanning by evaluating echo-planar time-series data from the eyes. RESULTS: Compared to the healthy subjects, the patients with schizophrenia exhibited greater activity in both posterior hippocampi and the right fusiform gyrus during smooth pursuit eye movements. The region-of-interest analysis revealed subtle activity deficits in frontal and occipital regions in the patients with schizophrenia. Smooth pursuit deficits in the subjects with schizophrenia included lower gain (eye velocity relative to target velocity) and a higher percentage of total eye movements due to anticipatory saccades, compared with the healthy subjects. CONCLUSIONS: The observed group differences are consistent with evidence for diminished inhibitory function in the hippocampus as well as for a disturbance in a frontotemporal network subserving smooth pursuit eye movements in schizophrenia.
Adult↗
The extraretinal signal from the pursuit-eye-movement system: its role in the perceptual and the egocentric localization systems.
The accuracy of perceptual judgment of the distance of a moving target tracked at various velocities by pursuit eye movements was examined in relation to the amount of two types of eye movement (smooth pursuit eye movement and compensatory saccade) involved in eye tracking. The perceptually judged distance became shorter as the amount of pursuit-eye-movement component in eye tracking increased. A detailed analysis of the eye-movement data and the size of perceptual underestimation indicated that the underestimation was mainly caused by inaccurate extraretinal information derived from the pursuit-eye-movement system, which underestimated the distance at a constant ratio, irrespective of the velocity of tracking. Egocentric localization was not affected by the mode of eye movements, indicating that the egocentric localization system functions without interference from the inaccurate information from the pursuit-eye-movement system.
Adult↗
Evidence for nonretinal feedback in combined version-vergence eye movements.
Recently, a quantitative model for the general of rapid eye movements in direction and depth was proposed. In this scheme, the saccadic and the vergence system share a common initiation system and are controlled by local feedback loops based on efference copy signals. We have used a remembered-target double-step paradigm to test the idea that both subsystems are guided by extraretinal signals. The subject was instructed to move the binocular point of fixation to the remembered positions indicated by a double-step movement of the target, in direction and depth. Since both binocular refixations were made in complete darkness, correct execution of this task requires information about both the stored visual coordinates of the final target and the coordinates of the first movement. Binocular eye movements from five subjects were compared with predictions from two feed-forward models and a feedback model. Analysis of the pooled direction data showed that the feedback model performed best and fitted well. Qualitatively the same result was obtained in the vergence component, but in this case the goodness of fit was considerably less. These results, confirmed in each individual subject, show that the saccadic and vergence subsystem can use nonretinal information about a prior movement in direction and depth. Further analysis showed that the gain of the direction response of the second movement was, on average, roughly correct. By contrast, the vergence component of these responses was only about 60% of the required amplitude. Since the fit procedure gave the same weighting factors to the second target and to the first movement, we propose that the low vergence gain reflects mechanisms operating after the calculation of the motor error signal, possibly at the execution stage. Finally, we discuss the possibility of a central control stage keeping track of the ongoing movement sequence, based on a comparison of desired and current eye position signals.
Adult↗
The objective assessment of abnormal eye movements in infants and young children.
Recordings of eye movements from infants and young children can be of clinical value in patients with certain neuro-ophthalmological problems. This requires that the characteristics of normal eye movements in this same age-group are known. Using an electro-oculographic technique in a specially developed laboratory we have been able to assess the saccades, binocular and monocular smooth pursuit, binocular and monocular optokinetic nystagmus (OKN), and sustained vestibular rotation in infants and young children; these recordings were performed in one session lasting approximately 35 minutes. The recordings from four children with abnormal eye movements (delayed visual maturation, hemicerebral cyst, congenital ocular motor apraxia, and gaze-paretic nystagmus) are briefly reported and compared to normal eye movements of age-related children. The limitations of this procedure are discussed.
Adolescent↗
Human smooth and saccadic eye movements during voluntary pursuit of different target motions on different backgrounds.
Horizontal and vertical eye movements of ten human subjects were recorded with a scleral induction-coil technique during voluntary pursuit of sinusoidal, triangular and pseudo-random target motions of different frequency, amplitude and dimensionality upon a dark, diffuse or structured background. Data processing included separation of the composite eye movement into a cumulative smooth and saccadic displacement, computation of gain and phase of the composite and smooth eye movements with respect to the target movement and analysis of retinal position error. Pursuit eye movements were never completely smooth. Smooth pursuit gain was always lower than 0.95 and saccades were used to supplement the smooth eye movements in pursuing the target with the proper amplitude. The gain of composite eye movements was about unity for sinusoidal target motions and ramps; it exceeded unity for the highest frequency components in a pseudo-random motion. The gain of the smooth eye movements decreased monotonously whenever target velocity increased. It was higher for single sine waves than for a pseudo-random motion, however, with pseudo-random motion it was relatively higher for the higher frequency components. Phase lags were in general smaller for single sine waves than for pseudo-random motion, but for the latter a phase lead of the smooth component was consistently found for the lower frequency components. During pursuit of a rhomboid trajectory, the eye movements showed directional errors which are interpreted as anticipatory behaviour. The distribution of the retinal error was symmetrical around zero. Its standard deviation varied between about 0.2 and 1.3 degrees; it was about proportional to target velocity and inversely proportional to smooth pursuit gain. It was limited by the insertion of saccades which were in general corrective. The influence of a diffusely illuminated background was minimal. A structured background inhibited smooth pursuit in the horizontal direction by about 10% and in the vertical direction by about 20%. This deficit of smooth pursuit was fully compensated by the insertion of more saccades and had no consequences for the standard deviation of the retinal error. The type of structure of the background was only of marginal importance. Horizontal pursuit was in general slightly smoother and more precise than vertical pursuit.
Adult↗
The properties of convergence eye movements evoked from the rostral and caudal lateral suprasylvian cortex in the cat.
Convergence eye movements were evoked in the lateral suprasylvian cortex (LS cortex) in the cat. Three effective regions were found: the rostral and caudal parts of the postero-medial LS cortex (the PMLS) and the rostral part of the postero-lateral LS cortex (the PLLS). These three areas represent the central and paracentral visual fields in the published retinotopic map (Palmer et al., 1978). Convergence eye movements evoked from the caudal PMLS were divided into two groups based on their latencies; the short-latency components (SLC) and long-latency components (LLC). The SLC and the LLC had differences in their symmetry of right and left eye movements during vergence eye movement. The SLC had symmetric right and left eye components and the LLC had dominant contralateral eye components. In the rostral PMLS, latencies of evoked convergence eye movement were comparable to those of the caudal PMLS, but they did not divided into two groups. Convergence eye movements evoked from the PLLS had longer latencies than those from the PMLS and asymmetric right and left eye components. It is suggested that different subregions in the LS cortex contribute to the control of convergence eye movement, playing different roles.
Animals↗
Voluntary selection of the target for smooth eye movement in the presence of superimposed, full-field stationary and moving stimuli.
Prior work has shown that smooth eye movements in the presence of both stationary and moving stimuli are determined, at least in part, by the voluntary selection of either the stationary or the moving stimulus as the target for smooth eye movements. The effectiveness of voluntary selection in eliminating the influence of the stimuli not selected (i.e. backgrounds) on smooth eye movement is not known because prior studies used targets and backgrounds with different physical characteristics. Thus, effects of voluntary selection were confounded with the relative strength of target and background as stimuli for smooth eye movements. We measured eye movements (resolution 1') of two highly-experienced eye movement subjects with a target and background with the same physical characteristics: two, identical, full-field, superimposed patterns of randomly-positioned dots (1 dot/deg2 or 8 dots/deg2). One field was stationary and the other moved at 70.2 minarc/sec. The effect of the moving background on smooth eye movements when the stationary field was the target, and the effect of the stationary background on smooth eye movements when the moving field was the target was negligible (0-4% for one subject; 0-2% for the other). The influence of the background on smooth eye movements was affected by a six-fold reduction in the intensity of either the target or background, but effects of such intensity changes were small and different for each subject. Taken together, these results show that the effectiveness of voluntary selection in eliminating the influence of background stimuli on smooth eye movements can be virtually complete. Any observed influence of the background--however small--can be attributed to voluntary factors (e.g. subjects' failure to apply sufficient effort or attention) rather than to the operation of an involuntary mechanism that automatically integrates velocity information from target and background. The attention and effort required to ensure that voluntary selection is perfect may impair the accuracy of psychophysical judgments made about the background.
Attention↗
Estimating heading during eye movements.
In eight experiments, we examined the ability to judge heading during tracking eye movements. To assess the use of retinal-image and extra-retinal information in this task, we compared heading judgments with executed as opposed to simulated eye movements. In general, judgments were much more accurate during executed eye movements. Observers in the simulated eye movement condition misperceived their self-motion as curvilinear translation rather than the linear translation plus eye rotation that was simulated. There were some experimental conditions in which observers could judge heading reasonably accurately during simulated eye movements; these included conditions in which eye movement velocities were 1 deg/sec or less and conditions which made available a horizon cue that exists for locomotion parallel to a ground plane with a visible horizon. Overall, our results imply that extra-retinal, eye-velocity signals are used in determining heading under many, perhaps most, viewing conditions.
Algorithms↗
Resolution of lexical ambiguity: evidence from an eye movement priming paradigm.
Subjects' eye movements were monitored while they read 2-sentence passages of text. A target-word region was defined in the 2nd sentence of each passage. During the initial 35 ms of a target region eye fixation, an ambiguous word was presented as a prime. A target word subsequently replaced the prime during the fixation. Priming was measured by comparing fixation times on targets preceded by semantically related versus unrelated ambiguous primes. The type of prior context (consistent vs. inconsistent), type of ambiguous prime (biased vs. balanced), and strength of instantiated meaning (dominant vs. subordinate) could all affect priming. Priming effects were only found when the prior context was consistent with the dominant sense of a biased ambiguous prime. The results are discussed in terms of models of ambiguity resolution: The data seem most consistent with a reordered access model.
Eye Movements↗