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At least 235 records · Page 13Linked to original sources
PubMed2001

Relationship between exploratory eye movements and clinical course in schizophrenic patients.

Exploratory eye movements are psychophysiological indicators of schizophrenia as well as smooth pursuit eye movements. To investigate whether these eye movements change in accordance with the clinical course of the condition in schizophrenia, exploratory eye movements (number of eye fixations, mean eye scanning length, responsive search score, evaluation of reproduced Fig. 1 and 2) of 28 schizophrenic patients were evaluated in repeat test design, conducted an average of 8 months apart. Subjects were first-medicated schizophrenics, half were outpatients and the remaining half were inpatients at the Neuropsychiatry ward of Tokyo Medical and Dental University Hospital. Exploratory eye movement patterns did not improve despite an improvement in clinical symptoms of schizophrenia. This result and those of previous studies of the exploratory eye movements of schizophrenic patients' families suggest that exploratory eye movements reflect a schizophrenic vulnerability marker. Furthermore, decreased mean eye scanning length (MESL) values were observed in subjects who showed unimproved symptoms, particularly negative symptoms over an extended period of time. The result suggests that a decrease in the MESL value may be the most sensitive indicator in the development of chronicity in schizophrenia.

Adolescent↗
PubMed1982

Cerebellar control of fixation eye movements.

Human subjects normally have miniature eye movements during tasks that require steady visual fixation. These eye movements were compared in 12 control subjects and 4 patients with degenerative cerebellar disorders. Slow drifts, small fixation saccades, square waves, saccadic oscillations, flutter, and vertical nystagmus occurred in both control subjects and patients. In the patients, however, fixation eye movements were enlarged and square waves and saccadic oscillations were more frequent. It appears that some forms of pathologic fixation instability are due to defective cerebellar control of fixation eye movements, and that precise measurements of these eye movements may quantitate disorders of cerebellar function.

Adolescent↗
PubMedDate not supplied

A reexamination of "neck reflex" eye movements in the rabbit.

Horizontal eye movements of rabbits were recorded during sinusoidal oscillation (15-40 degrees, pk-pk; 0.1-8 Hz) and step displacement of the body in yaw about a fixed head. Modulated, slow-phase eye movements followed all frequencies of stimulus with relatively invariant amplitudes (2-4 degrees). Saccadic movements, up to 17 degrees, accompanied all frequencies of oscillation and particularly step displacements. Saccadic amplitude was unrelated to measurable characteristics of the stimuli but was a function of arousal. The latency of any eye movement was a minimum of 80 msec. It is concluded that none of the observed eye movements provide stabilization during head movements but are evidence of the contribution of neck information to general mechanisms of whole body orientation.

Animals↗
PubMed1978

Role of primate flocculus during rapid behavioral modification of vestibuloocular reflex. II. Mossy fiber firing patterns during horizontal head rotation and eye movement.

1. Extracellular recordings were obtained from 113 mossu fibers (MFs) in the flocculus of alert monkeys trained to perform a visual tracking task during sinusoidal, horizontal head rotation. The analysis of MF discharge patterns was designed to allow quantitative comparison of the discharge properties of flocculus MFs with brain stem cell populations from which the MFs might originate and with flocculus Purkinje cells (P-cells). Based on their firing patterns, MFs were divided into two classes. Vestibular MFs discharged in relation to head velocity and, in some cases, also in relation to eye movement. Eye movement MFs discharged only in relation to one or more components of eye movement. 2. Vestibular MFs were subdivided into three classes. Vestibular-only MFs (n = 15) displayed a modulation in firing rate during head rotation but exhibited no relationship to spontaneous eye movements. Vestibular-plus-saccade MFs (n = 14) displayed a modulation in firing rate during head rotation that quantitatively resembled the modulation in vestibular-only MFs. In addition, a pause in firing rate interrupted the vestibular modulation during saccades in one or more directions. Vestibular-plus-position MFs (n = 4) exhibited steady firing rates that were linearly related to horizontal eye position in the absence of vestibular stimulation. Sinusoidal head rotation evoked a modulation ofiring rate above and below the firing rate set by the eye position. 3. during sinusoidal head rotation, vestibular MF firing rate led head velocity by an average of 24 degrees. The amplitude of MF firing-rate modulation increased as a function of the frequency of head rotation and, hence, maximum head velocity. Since these characteristics are similar to those displayed by P-cells during suppression of the VOR, vestibular MFs probably transmit the head velocity component of P-cell firing rate to the flocculus. Based on evidence from other mammals and a quantitative comparison of population discharge characteristics, it is likely that vestibular MFs originate from the vestibular nerve and from cells in the medial vestibular nucleus. 4. Based on their discharge patterns, eye movement MFs were also subdivided into three classes. Burst MFs (n = 14) emitted a high-frequency burst of spikes prior to and during saccades in one or more direction, but were silent during steady fixation. Burst-tonic MFs (n = 53) emitted a burst of spikes prior to saccades in a preferred ("on") direction, ceased firing during saccades in the opposite ("off") direction, and exhibited steady firing rates that increased as steady gaze shifted in the on direction. Tonic MFs (n = 13) displayed steady firing rates that increased as the position of steady gaze shifted in the on direction, and either paused or exhibited step changes in firing rate during saccades. 5. During steady fixation, 64% of tonic and burst-tonic MFs were recruited into maintained firing within +/- 10 degrees of the primary direction of gaze...

Animals↗
PubMed2006

Using reinforcement learning to understand the emergence of "intelligent" eye-movement behavior during reading.

The eye movements of skilled readers are typically very regular (K. Rayner, 1998). This regularity may arise as a result of the perceptual, cognitive, and motor limitations of the reader (e.g., limited visual acuity) and the inherent constraints of the task (e.g., identifying the words in their correct order). To examine this hypothesis, reinforcement learning was used to allow an artificial "agent" to learn to move its eyes to read as efficiently as possible. The resulting patterns of simulated eye movements resembled those of skilled readers and suggest that important aspects of eye-movement behavior might emerge as a consequence of satisfying the constraints that are imposed on readers. These results also suggest novel interpretations of some contentious empirical results, such as the fixation duration costs associated with word skipping (R. Kliegl & R. Engbert, 2005), and theoretical assumptions, for example the familiarity check in the E-Z Reader model of eye-movement control (E. D. Reichle, A. Pollatsek, D. L. Fisher, & K. Rayner, 1998).

Algorithms↗
PubMed2003

Eye movements provide the extra-retinal signal required for the perception of depth from motion parallax.

It has been unclear whether the perception of depth from motion parallax is an entirely visual process or whether it requires extra-retinal information such as head movements, vestibular activation, or eye movements. Using a motion aftereffect and static test stimulus technique to eliminate visual cues to depth, this psychophysical study demonstrates that the visual system employs a slow eye movement signal, optokinetic response (OKR) in particular, for the unambiguous perception of depth from motion parallax. A vestibular signal, or vestibularly driven eye movement signal is insufficient for unambiguous depth from motion parallax. Removal of the OKR eye movement signal gives rise to ambiguous perceived depth in motion parallax conditions. Neurophysiological studies suggest a possible neural mechanism in medial temporal and medial superior temporal cortical neurons that are selective to depth, motion, and direction of eye movement.

Depth Perception↗
PubMed1983

Eyeglasses, height, and lateral eye movements.

Conformity to the lateral eye movement patterns of (1) a preferred direction in a face-to-face situation and (2) direction contralateral to the cerebral hemisphere tapped by a question in a nonface-to-face situation was studied in forty right-handed male college students in four groups: (1) Normal vision (N = 10), (2) Nearsighted wearing glasses full-time (N = 10), (3) Nearsighted wearing contact lenses (N = 10), and (4) Nearsighted wearing glasses part-time (N = 10). Subjects were of normal weight with no familial left-handedness or psychiatric hospitalization and no ocular or visual problems other than nearsightedness. Ratings of eye movement direction were made from videotapes. Subjects wearing glasses full-time or part-time were significantly more likely than other subjects to show the contralateral eye movement pattern in the nonface-to-face situation (p less than 0.05). Tall subjects showed more up eye movements (p less than 0.05). These findings were interpreted as an effect of long-standing visual expectancies. Myopic subjects were significantly more likely to be left-lookers than right-lookers (p less than 0.05).

Body Height↗
PubMed2002

[Binocular rivalry in half-occluded region is weakened by eye movement].

To investigate the effect of eye movement on suppression of binocular rivalry in the half-occluded region, which is the monocular region made by occlusion, the amount of binocular rivalry in the half-occluded region was measured in the eye movement condition and the fixating condition. In the eye movement condition, the observer moved their eyes between the occluder and the occluded object. In the fixating condition, the observers fixated the occluder (the fixating-the-occluder condition) or the occluded object (the fixating-the-occluded-object condition). Following facts were found: (a) the amount of binocular rivalry in the half-occluded region reduced more in the eye movement condition than in the two fixating conditions, (b) there was no significant difference in the amount of binocular rivalry in the half-occluded region between the two fixating conditions. These results suggested that eye movement is one of the factors to suppress binocular rivalry in the half-occluded region in natural viewing situations.

Eye Movements↗
PubMed2006

What clinical disorders tell us about the neural control of saccadic eye movements.

Saccades are rapid eye movements that redirect the fovea from one object to another. A great deal has been learned about the anatomy and physiology of saccades, making them an ideal system for studying the neural control of movement. Basic research on normal eye movements has greatly increased our understanding of saccadic performance, anatomy and physiology, and led to a large number of control system models. These models simulate normal saccades well, but are challenged by clinical disorders because they often do not incorporate the specific anatomical and physiological substrates needed to model clinically important abnormalities. Historically, studies of saccadic abnormalities in patients have played a critical role in understanding the neural control of saccades because they provide information that complements basic research and thus restricts hypotheses to those that are biologically plausible. This review presents four examples of clinical disorders (slow saccades, interrupted saccades, high-frequency saccadic oscillations and macrosaccadic oscillations) that have provided insights into the neurobiology of saccades, have driven the development of new models, and have suggested an explanation or treatment for these disorders. We raise general questions for both scientists and clinicians that will assist in their efforts to understand the neural control of movement, improve diagnostic criteria and develop new treatments.

Brain↗
PubMed2003

Effects of procyclidine on eye movements in schizophrenia.

Smooth pursuit eye movement (SPEM) and antisaccade deficits are observed in the schizophrenia spectrum and have been used to study the pathophysiology as well as the genetic basis of this condition. The neurotransmitter acetylcholine has been implicated in a number of cognitive processes thought to underlie SPEM and antisaccade performance. This study investigates effects on eye movements of procyclidine, an anticholinergic drug often administered to schizophrenic patients. A total of 13 patients completed a double-blind placebo-controlled crossover design, receiving 15 mg procyclidine and placebo. Seven participants received procyclidine first and placebo second, six participants were tested in the reverse order. SPEM and antisaccade (as well as fixation and prosaccade) eye movements were recorded using infrared oculography. Results showed that procyclidine overall, relative to placebo, mildly worsened SPEM performance, as indicated by nonsignificantly reduced gain (p=0.08) and increased frequency of intrusive anticipatory saccades during pursuit (p=0.06). A significant interaction of group and order of administration indicated that procyclidine increased the rate of antisaccade reflexive errors only when administered first; the opposite pattern was observed when placebo was administered first, likely due to the operation of practice effects at second assessment. These findings indicate that acute administration of a clinically relevant dose of procyclidine leads to mild impairments in eye movement performance in schizophrenic patients, suggesting the need to consider this compound in oculomotor studies in schizophrenia. The action of this anticholinergic drug on oculomotor performance is consistent with the hypothesized role of the cholinergic system in the cognitive mechanisms of attention and working memory, processes thought to underlie SPEM and antisaccade performance. Effects of order of administration and practice on the antisaccade task suggest that these factors need to be taken into consideration in future pharmacological studies.

Adult↗
PubMed1989

Limited eye movement patterns in chronic schizophrenic patients.

Eye movements of 29 chronic schizophrenic patients and 23 normal control subjects were measured by an eye mark recorder during viewing of stationary geometric figures. The results suggested that the eye movements of schizophrenic patients were more limited than those of normal control subjects and that the abnormal eye movement inspection patterns in schizophrenic patients may reflect a lack of visual investigation of novel stimuli in the environment. Our findings, together with Moriya's (1979) observation of similar eye movement pattern abnormalities in the relatives of schizophrenic patients, support the hypothesis that the limited eye movement patterns may be a biological marker for schizophrenia.

Adult↗
PubMed2005

Attention and selection for predictive smooth pursuit eye movements.

Humans cannot typically produce smooth eye movements in the absence of a moving stimulus. However, they can produce predictive smooth eye movements if they expect a target of a known velocity to reappear. Here, we observed that participants could extract velocity information from two simultaneously presented moving targets in order to produce a subsequent predictive smooth eye movement for one of the two targets. Subjects fixated a stationary cross during the presentation of two targets, moving rightward at different velocities. In the next presentation, a single target was presented, which participants tracked with their eyes. A static cue, presented 700 ms before the moving target, indicated which of the two targets would be presented. Predictive eye movements were of an appropriate velocity, even when participants did not know in advance which of the two targets would subsequently be cued. However, the scaling of predictive eye velocity was marginally less accurate in this divided attention condition than when participants knew the identity of the cued target in advance, or a single target was presented during fixation. In a second experiment, we found that the velocity cued on the previous trial had a greater effect than the uncued velocity on the current trial. The negligible effect of the uncued velocity indicates that participants were extremely effective at selectively reproducing one of two recently viewed velocities. However, other influences, such as past history, also affected predictive smooth eye movements.

Adult↗
PubMed1985

Accuracy of spatial localizations near the time of saccadic eye movements.

Two-dimensional eye movements were recorded while subjects used a hammer to strike targets that were flashed-on briefly before, during or up to 750 msec after a horizontal saccade. Mean position of hammer blows was 20 min arc (SD = 67 min arc) from the target when the only cue to target location was eye position. Position of responses varied slightly with time of target exposure relative to the saccade. These results show that observers can closely monitor small changes in eye position during and near the time of saccadic eye movements.

Eye Movements↗
PubMed1980

Studies of parkinsonian movement: 2. Initiation of fast voluntary eye movement during postural disturbance.

Delay in initiation of rapid voluntary eye movements (saccades) in bradykinetic parkinsonian patients and normal subjects was recorded with and without postural disturbances (rotation of the body and head). Parkinsonian patients as a group exhibited longer delays in the initiation of saccades. The delay increased during postural disturbance in both the patients and the normal subjects. The study failed to substantiate the hypothesis that postural reflexes interfere with the initiation of voluntary movement in Parkinsonism.

Adult↗
PubMed1981

Human fetal eye movements: detection in utero by ultrasonography.

Eye movements of the human fetus were detected in utero by means of real-time B-scan and M-mode ultrasonography. In 14 low-risk fetuses studied between 32 weeks menstrual age and term either rapid or slow eye movements or a mixture of both types were detected in 60 +/- 10% (mean +/- SD) of 558 2 min scoring epochs. A comparison of direct echoscopic detection of eye movements in a 3-day-old neonate confirmed that the movements observed in the orbital region with the real-time scanner corresponded well with eye movements seen directly. Thus eye movements can be added to the list of phenomena which can be observed noninvasively for the study of human fetal behaviour.

Age Factors↗
PubMed1985

Human eye movements associated with blinks and prolonged eyelid closure.

Eye movements associated with eyelid closure were recorded in human subjects with search coils, embedded in self-adhering scleral annuli, in a magnetic field. In contrast to classical notions, voluntary as well as reflex blinks were consistently accompanied by transient downward and nasalward movements of both eyes with amplitudes 1-5 degrees. These eye movements had a shorter duration than the upper lid movements, and the shapes of the spatial trajectories of eye and lid movements were not similar. The trajectory of the eye movements was only modestly affected by gaze eccentricities up to 15 degrees; there was a tendency for the downward component to be enhanced by looking upward, and vice versa. Restraining of the lids of one eye in the open or closed position did not significantly alter the eye movements during (attempted) blinks. Velocity-amplitude-duration relations of the down- and upward components were similar for the same eye before and after closure and for the closed eye and the contralateral unrestrained eye. The velocity-amplitude-duration characteristics of saccades were also unaffected by prolonged closure of the lids of one eye. Prolonged, voluntary closure of the lids was followed by a slow, tonic ocular deviation, which was consistently upward in half of the subjects and consistently downward in the other half. Additional horizontal components were highly variable even within subjects. In one subject the downward deviation was converted into upward deviation when lid closure was mechanically impeded. We conclude that elevation of the eye ball (Bell's phenomenon) does not occur during short blinks and only in about half of the subjects during voluntary unrestrained prolonged lid closure. Our evidence does not support the possibility that the transient eye movements during blinks are caused primarily by a mechanical interaction between the lids and the eye (or the scleral annulus). More likely, they are a secondary effect of an active cocontraction of extraocular muscles that primarily results in retraction of the eye.

Adult↗
PubMed1989

Effect of a scotoma on eye movements during visual search.

Eye movements have been recorded during a free visual search task both with and without an artificial foveal scotoma. Results of the eye movement measurements show that neither fixation durations nor mean saccade amplitudes are significantly modified by the loss of foveal vision.

Analog-Digital Conversion↗