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PubMed2006

[Eye movement in patients with schizophrenia].

To clarify the cognitive function of schizophrenia, the exploratory eye movement was investigated using S-shaped figures in patients with schizophrenia and their relatives. As a result, the exploratory eye movement has been found to be a biological marker that reflects a specific and trait factor of schizophrenia. Using the exploratory eye movement combined with brain functional imaging, the pathology of schizophrenia that the neural network centering on thalamus was damaged is being clarified. Moreover, the disease gene of schizophrenia may be discovered especially on the chromosome 22 using the exploratory eye movement as an endophenotype. In addition, the exploratory eye movement can be given as a powerful candidate of diagnostic tool for schizophrenia.

Adult↗

PubMed2004

Covert shifts of attention precede involuntary eye movements.

There is considerable evidence that covert visual attention precedes voluntary eye movements to an intended location. What happens to covert attention when an involuntary saccadic eye movement is made? In agreement with other researchers, we found that attention and voluntary eye movements are tightly coupled in such a way that attention always shifts to the intended location before the eyes begin to move. However, we found that when an involuntary eye movement is made, attention first precedes the eyes to the unintended location and then switches to the intended location, with the eyes following this pattern a short time later. These results support the notion that attention and saccade programming are tightly coupled.

Adult↗

PubMedDate not supplied

Use of infrared TV cameras built into head-mounted display to measure torsional eye movements.

PURPOSE: The head-mounted display (HMD) has produced conflict between visual and vestibular stimuli because the HMD image does not move with the head motion of the wearer. The HMD can show binocular parallax three-dimensional (3D) images, in which vergence and accommodation conflict. Thus, the HMD may affect the normal visual/vestibular functions. We attempted to develop a system that makes possible the measurement of torsional eye movements, vergence eye movements, and pupillary responses of the HMD wearer. METHODS: Our apparatus is composed of two infrared CCD cameras installed in the HMD. Iris images produced by these cameras are analyzed by a personal computer using free software. Further, a third camera fixed on the HMD projects an image of the view as the subject sees it, via video tape recorder or frame memory to the HMD. Images can be stored, replayed, or frozen. RESULTS: Our system can measure torsional eye movement with 0.20 degrees resolution every 1/30 (or 1/60) seconds even though the pupil size alternates during measurement. Binocular eye movement and pupillary response are also measured. CONCLUSION: A system was developed which can be used for assessment of the effect of 3D HMD on the visual system. A third camera coupled with HMD can control visual stimulus independently of head motion (vestibular stimulus).

Eye Movements↗

PubMed2003

3D eye movement analysis during sinusoidal off vertical axis rotation in human subjects.

OBJECTIVE: It has been reported that the eye movements induced by off vertical axis rotation (OVAR) are composed of two components: a bias component (BIC) and a modulation component (MOC). It was suggested that the MOC compensates for changes in head orientation with respect to gravity and that the BIC is related to the velocity storage mechanism. However, the characteristics of the otolith organs remain obscure. In order to investigate these characteristics, we performed a 3D analysis of eye movements induced by human sinusoidal s-OVAR, and compared the result with that of eye movements induced by constant c-OVAR. MATERIAL AND METHODS: Fifteen healthy human subjects participated in this study. OVAR stimulation was produced by rotation following tilt. After a 30 degrees tilt, the subject was rotated sinusoidally at 0.05 and 0.02 Hz at 50 degrees/s peak velocity. Eye movements were recorded using an infrared charge-coupled device camera, and the updated version of our standard computerized image recognition method was used to analyze them three-dimensionally. RESULTS: The eye movements induced by s-OVAR consisted of two kinds of sine waves: low- and high-frequency components. The low-frequency component was related to the change in angular acceleration, and the eye movements were found to derive from the semicircular canals. In contrast, the high-frequency component was related to the change in head position, and the eye movements were found to derive from the otolith organs. CONCLUSION: s-OVAR may prove to be a useful tool for simultaneously assessing the functions of both the otolith organs and the semicircular canals.

Adult↗

PubMed1991

The interstitial nucleus of Cajal in the midbrain reticular formation and vertical eye movement.

Bilateral lesions of the midbrain reticular formation within, and in the close vicinity of, the interstitial nucleus of Cajal (INC) result in the severe impairment of the ability to hold eccentric vertical eye position after saccades, phase advance and decreased gain of the vestibulo-ocular reflex (VOR) induced by sinusoidal vertical rotation. In addition, the INC region of alert animals contains many burst-tonic and tonic neurons whose activity is closely correlated with vertical eye movement, not only during spontaneous saccades, but also during the VOR, smooth pursuit and optokinetic eye movements. Although their activity is closely related to these conjugate vertical eye movements, it is different from the oculomotor motor neuron activity. These results indicate that the INC region is involved in, and indispensable for, some aspects of eye position generation during vertical eye movement. Further comparison of INC neuron discharge with eye movements during two special conditions indicates that the INC region alone cannot produce eye position signals. First INC neuron discharge shows no response or an 80 degrees phase advance (close to the expected value if there is no integration) in the dark compared to the light during sinusoidal vertical linear acceleration in alert cats. Second, during rapid-eye-movement (REM) sleep, the discharge of INC neurons is no longer correlated with eye position. These results imply that the INC is not the entire velocity-to-position integrator, but that it has to work with other region(s) to perform the integration. A close functional linkage has been described between vertical-eye-movement-related neurons in the INC region and vestibulo-ocular relay neurons related to the vertical semicircular canals in the vestibular nuclei. It has been suggested that both are the major constituents of the common neural integrator circuits for vertical eye movements.

Animals↗

PubMed1994

Visual fields and eye movements in herons (Ardeidae).

The visual fields and eye movements of three heron species (Ardeidae; Ciconiiformes): the cattle egret (Bubulcus ibis), the squacco heron (Ardeola ralloides), the western reef heron (Egretta gularis schistacea) were determined in alert, restrained birds using an ophthalmoscopic technique. All three species can gain panoramic visual coverage of the frontal field around the bill, and a bird standing with its bill horizontal can view its own feet binocularly. The region in which binocular overlap is possible is long (approximately 170 degrees) and narrow (maximum width approximately 20 degrees). Monocular field width in a horizontal plane is approximately 170 degrees. Retinal binocular overlap can be abolished by eye movements at all elevations in the frontal field. At the frontal margins of the monocular fields the retinal and optical field margins do not coincide; the retinal field margin lies between 9 degrees and 12.5 degrees inside the optical field margin. This results in a blind sector at the margin of each eye's optical field. Consequently the visually functional retinal binocular field widths are significantly narrower than the optical binocular fields. When retinal binocularity is abolished by eye movements, optical binocular fields are still retained. Thus, estimates of binocular overlap based only upon the appearance of the pupils will be erroneous. The comprehensive nature of vision beneath the bill is probably closely associated with the herons' visually guided, stealthy, foraging techniques, which result in the single-strike capture of mobile, highly evasive prey.

Animals↗

PubMed1990

Quantitative analysis of eye movements during REM-sleep in developing rats.

Development of eye movements in REM-sleep was studied in rats during the second and third week of postnatal life. An increased frequency of eye movements was found after eye opening, which was due only to changes in burst activity. Since pups reared in constant darkness showed an increase in eye movement activity similar to that of those exposed to diurnal light-dark alterations, the change seems to be part of an endogenous developmental timetable rather than due to an increase of visual stimulation by eye opening.

Animals↗

PubMed2005

Relationship between eye movement period and micturition in newborn infants differs from that of human fetuses at term.

AIM: To investigate the relationship between the onset of eye movement periods and micturition in human fetuses and in neonates with the intention of clarifying the transition in relationship during the perinatal period. METHODS: Data were acquired during 1-4 days and/or 1 month (29-33 days) from 6 normal neonates born at term. Eye movements, crying, and eye open periods were observed with a video recorder until micturition occurred. In 29 term fetuses, the time lag between the onset of an eye movement period and micturition was measured by real-time ultrasound instruments. RESULTS: The time lag between the onset of an eye movement period and micturition in neonates (2 minutes; range, 0-57 minutes) was significantly (P=0.027) different from the time lag for fetuses (14 minutes; range, 2-32 minutes) and the frequency of micturition occurring within 8 minutes (33) was significantly lower (P=0.017) than that seen for term fetuses (72%). CONCLUSION: The relationship between the onset of an eye movement period and micturition is different in term human fetuses and neonates of less than 1 month of age. This suggests that the neuronal relationship among brain centers for micturition, rapid-eye-movement sleep, and awakening is dramatically altered perinatally.

Arousal↗

PubMed1976

Lightning eye movements.

Physiologic studies were performed on a patient who demonstrated lightning eye movements, palatal myoclonus and myoclonic jerks of the left platysma and sternocleidomastoid muscles. The myoclonus and lightning eye movements were separate phenomena with no defined relationship to each other. Analysis of this ocular dyskinesia identified strictly horizontal saccadic oscillations, 2 to 5 Hz in frequency, with amplitudes varying greatly but often reaching 25 degrees. A brief stationary period between each saccadic oscillation was frequently observed. They were particularly induced by vertical or horizontal ocular pursuit as well as sustained upward or downward ocular deviation. Caloric nystagmus abolished the oscillations but they persisted, irregularly, during optokinetic nystagmus. Thus a faulty visual fixation mechanism is postulated to precipitate lightning eye movements. Constrast studies revealed a mass lesion arising from the right dorsolateral portion of the medulla. These results indicate that lightning eye movements occur with caudal as well as rostral brain-stem lesions. From the clinical findings cerebellar pathway involvement is likely.

Adult↗

PubMed2000

Infusion of adenylyl cyclase inhibitor SQ22,536 into the medial pontine reticular formation of rats enhances rapid eye movement sleep.

Microinjection of cholinergic and adenosinergic agonists into the medial pontine reticular formation of rats produces long lasting increases in the time spent in rapid eye movement sleep. Several G-protein-coupled muscarinic and adenosinergic receptors share a common action of inhibition of adenylyl cyclase and inhibition of cyclic adenosine monophosphate. Inhibition of cyclic adenosine monophosphate has been implicated in the mechanism of rapid eye movement sleep induction in the cat. We sought to determine whether a direct inhibitor of adenylyl cyclase microinjected into the rat reticular formation at sites where muscarinic and adenosinergic agonists are effective in producing long lasting elevations in rapid eye movement sleep also result in similar effects on the sleep/wake cycle. The caudal, oral pontine reticular formation was unilaterally infused with 60 nl volumes of carbachol (0.1-1.1mM) and N(6)-cyclohexyladenosine (0.1mM) each within 1h of lights on. Sites effective for significantly elevating rapid eye movement sleep for the 8h following microinjection of both receptor agonists were additionally injected with the adenylyl cyclase inhibitor, SQ22,536 (0.1M). Pontine injections of SQ22,536 resulted in significant mean increases in rapid eye movement sleep time and rapid eye movement sleep period frequency at all of these sites. As with the receptor agonists, SQ22,536 did not alter latency to rapid eye movement sleep onset. Rapid eye movement sleep amounts were observed to be significantly elevated by SQ22,536 at two days, but not at four days, following a single microinjection. These data implicate inhibition of cyclic adenosine monophosphate in the pons of the rat as a mechanism involved in the long-term modulation of rapid eye movement sleep. This mechanism may underlie the homeostatic regulation exhibited by this sleep-state.

Adenine↗

PubMed2006

Visual cortical contribution to open-loop and feed-back control of convergence eye movements in the cat.

Open-loop and closed loop controls in convergence eye movement have been reported by human psycho-physical studies. To investigate the visual cortical involvement in open-loop convergence eye movement, we trained a cat to elicit anticipatory convergence (convergence eye movement before the onset of target movement) by using an approaching visual target with a preceding alarm signal. After 1-2 weeks of training, anticipatory convergence was observed in more than half of the trials in seven cats. The frequency of occurrence of anticipatory convergence was significantly decreased after electrocoagulation in the convergence-related region of the lateral suprasylvian (LS) area, an extrastriate visual cortex of the cat. On the other hand, the localized injection of Muscimol, a GABA-A agonist, reduced visually evoked convergence, but caused no significant effects to anticipatory convergence. These differential results suggest that the LS plays a role in both open-loop and feed-back control of convergence eye movement, and a GABA-A sensitive subregion is involved in the feed-back control of convergence eye movement.

Animals↗

PubMed2003

Distribution of targets in 400 eye-movement desensitization cases.

In a series of 400 patients undergoing Eye-movement Desensitization (EMD), patients rarely reported more than nine flashbacks or other focal targets, which may indicate the working memory limit. Eye-movement desensitization may operate by freeing working memory capacity, enabling cognitive change and memory recovery to occur. Complete EMD treatment may require sufficient eye movements to free up working memory capacity. Patients given less than this requirement may not be adequately treated. This may account for variable results in evaluations of eye-movement desensitization. Such possible dose effects may be important in this therapy.

Adaptation, Psychological↗

PubMed1986

The effect of attentive fixation on eye movements evoked by electrical stimulation of the frontal eye fields.

Electrical stimulation of the frontal eye fields of the rhesus monkey evokes saccadic eye movements. Both the amplitude of electrically elicited saccades and the threshold current for eliciting them are primarily determined by the location of the stimulating electrode within the frontal eye fields; however, threshold and amplitude also are systematically affected by the monkey's behavioral state when the stimulation is applied. If the monkey is alert, but not performing a task, saccade amplitudes are largest and thresholds are lowest. Conversely, if the monkey actively fixates a visual target, elicited saccades are smaller and threshold currents are higher. Saccades evoked during fixation have slower velocities appropriate for their reduced amplitude. Phase plane plots of eye velocity versus eye position indicate that these saccades are originally programmed to be smaller and slower, and hence are not large saccades voluntarily braked in mid-flight. As opposed to their amplitude and threshold, the direction of electrically evoked saccades is unaffected by the state of fixation. The state of attentive fixation, but not the visual fixation target itself, is the responsible factor for these effects. These results suggest that there is a difference between the state of active fixation and the state of having the eye still in the orbit without active fixation. The oculomotor system in the latter case is relatively more susceptible to signals from the cerebral cortex.

Animals↗

PubMed1996

The primate frontal eye field and the generation of saccadic eye movements: comparison of lesion and acute inactivation/activation studies.

The frontal eye field (FEF) of monkeys has been repeatedly implicated in the generation of saccadic eye movements by various experimental approaches. Electrical stimulation of most of the FEF produces saccadic eye movements, many cells have activities related to saccades, and it has anatomical connections with many other oculomotor areas. Surprisingly, complete lesions of the FEF have remarkably little effect on oculomotor behavior. Only when more cognitive aspects are tested is a deficit clearly detected. In contrast, acute inactivation of the FEF of monkeys with the GABA agonist muscimol produced much more severe oculomotor impairment. This difference is probably due to the acute nature of the muscimol effect, which does not allow time for reorganization of the control of eye movements before testing begins. In addition, acute activation of the FEF with the GABA antagonist bicuculline caused the monkey to make irrepressible saccades of the same dimensions as those electrically elicited at the site. These experiments further confirm the strong involvement of the FEF in the control of saccadic eye movements and fixation.

Animals↗

PubMed2003

Visual tracking neurons in primate area MST are activated by smooth-pursuit eye movements of an "imaginary" target.

Because smooth-pursuit eye movements (SPEM) can be executed only in the presence of a moving target, it has been difficult to attribute the neuronal activity observed during the execution of these eye movements to either sensory processing or to motor preparation or execution. Previously, we showed that rhesus monkeys can be trained to perform SPEM directed toward an "imaginary" target defined by visual cues confined to the periphery of the visual field. The pursuit of an "imaginary" target provides the opportunity to elicit SPEM without stimulating visual receptive fields confined to the center of the visual field. Here, we report that a subset of neurons [85 "imaginary" visual tracking (iVT)-neurons] in area MST of 3 rhesus monkeys were identically activated during pursuit of a conventional, foveal dot target and the "imaginary" target. Because iVT-neurons did not respond to the presentation of a moving "imaginary" target during fixation of a stationary dot, we are able to exclude that responses to pursuit of the "imaginary" target were artifacts of stimulation of the visual field periphery. Neurons recorded from the representation of the central parts of the visual field in neighboring area MT, usually vigorously discharging during pursuit of foveal targets, in no case responded to pursuit of the "imaginary" target. This dissociation between MT and MST neurons supports the view that pursuit responses of MT neurons are the result of target image motion, whereas those of iVT-neurons in area MST reflect an eye movement-related signal that is nonretinal in origin. iVT-neurons fell into two groups, depending on the properties of the eye movement-related signal. Whereas most of them (71%) encoded eye velocity, a minority showed responses determined by eye position, irrespective of whether eye position was changed by smooth pursuit or by saccades. Only the former group exhibited responses that led the eye movement, which is a prerequisite for a causal role in the generation of SPEM.

Action Potentials↗

PubMed1991

Visual responses of pulvinar and collicular neurons during eye movements of awake, trained macaques.

1. We recorded from single neurons in awake, trained rhesus monkeys in a lighted environment and compared responses to stimulus movement during periods of fixation with those to motion caused by saccadic or pursuit eye movements. Neurons in the inferior pulvinar (PI), lateral pulvinar (PL), and superior colliculus were tested. 2. Cells in PI and PL respond to stimulus movement over a wide range of speeds. Some of these cells do not respond to comparable stimulus motion, or discharge only weakly, when it is generated by saccadic or pursuit eye movements. Other neurons respond equivalently to both types of motion. Cells in the superficial layers of the superior colliculus have similar properties to those in PI and PL. 3. When tested in the dark to reduce visual stimulation from the background, cells in PI and PL still do not respond to motion generated by eye movements. Some of these cells have a suppression of activity after saccadic eye movements made in total darkness. These data suggest that an extraretinal signal suppresses responses to visual stimuli during eye movements. 4. The suppression of responses to stimuli during eye movements is not an absolute effect. Images brighter than 2.0 log units above background illumination evoke responses from cells in PI and PL. The suppression appears stronger in the superior colliculus than in PI and PL. 5. These experiments demonstrate that many cells in PI and PL have a suppression of their responses to stimuli that cross their receptive fields during eye movements. These cells are probably suppressed by an extraretinal signal. Comparable effects are present in the superficial layers of the superior colliculus. These properties in PI and PL may reflect the function of the ascending tectopulvinar system.

Animals↗

PubMed2004

Eye movement control by the cerebral cortex.

PURPOSE OF REVIEW: This review focuses on eye movement control by the cerebral cortex, mainly in humans. Data have emerged based on the important contribution of recent techniques such as transcranial magnetic stimulation and functional magnetic resonance imaging, which provide complementary results to those of the classical lesion and electrical stimulation studies. RECENT FINDINGS: The location of the human frontal eye field and its role in pursuit eye movement control were recently detailed. Cumulative evidence for the role of the dorsolateral prefrontal cortex in unwanted reflexive saccade inhibition, short-term spatial memory and prediction suggests that this area controls decisional processes governing ocular motor behaviour. The organization of spatial memory in the dorsolateral prefrontal cortex (short-term), the parahippocampal cortex (medium-term) and the hippocampal formation (long-term) is also reviewed with the results of recent transcranial magnetic stimulation studies. The relatively complicated anatomy of the posterior parietal cortex in humans is briefly described followed by some additional results concerning the location of the parietal eye field - within the posterior half of the intraparietal sulcus - and its role in visuo-spatial integration and attention. The other areas involved in spatial attention are also examined in the light of several recent contributing reports. Lastly, there are also new functional magnetic resonance imaging findings concerning the posterior cingulate cortex, which appears to be mainly involved in the control of externally guided eye movements and attentional mechanisms. SUMMARY: Many new findings on the organization of saccades and pursuit eye movements at the cortical level have recently been reported. Furthermore, eye movements are increasingly used as a tool to elucidate relatively complex neuropsychological processes such as attention, spatial memory, motivation and decisional processes, and a considerable number of reports dealing with these questions have been observed.

Animals↗

PubMed1993

Monkey superior colliculus represents rapid eye movements in a two-dimensional motor map.

1. Although the eye has three rotational degrees of freedom, eye positions, during fixations, saccades, and smooth pursuit, with the head stationary and upright, are constrained to a plane by Listing's law. We investigated whether Listing's law for rapid eye movements is implemented at the level of the deeper layers of the superior colliculus (SC). 2. In three alert rhesus monkeys we tested whether the saccadic motor map of the SC is two dimensional, representing oculocentric target vectors (the vector or V-model), or three dimensional, representing the coordinates of the rotation of the eye from initial to final position (the quaternion or Q-model). 3. Monkeys made spontaneous saccadic eye movements both in the light and in the dark. They were also rotated about various axes to evoke quick phases of vestibular nystagmus, which have three degrees of freedom. Eye positions were measured in three dimensions with the magnetic search coil technique. 4. While the monkey made spontaneous eye movements, we electrically stimulated the deeper layers of the SC and elicited saccades from a wide range of initial positions. According to the Q-model, the torsional component of eye position after stimulation should be uniquely related to saccade onset position. However, stimulation at 110 sites induced no eye torsion, in line with the prediction of the V-model. 5. Activity of saccade-related burst neurons in the deeper layers of the SC was analyzed during rapid eye movements in three dimensions. No systematic eye-position dependence of the movement fields, as predicted by the Q-model, could be detected for these cells. Instead, the data fitted closely the predictions made by the V-model. 6. In two monkeys, both SC were reversibly inactivated by symmetrical bilateral injections of muscimol. The frequency of spontaneous saccades in the light decreased dramatically. Although the remaining spontaneous saccades were slow, Listing's law was still obeyed, both during fixations and saccadic gaze shifts. In the dark, vestibularly elicited fast phases of nystagmus could still be generated in three dimensions. Although the fastest quick phases of horizontal and vertical nystagmus were slower by about a factor of 1.5, those of torsional quick phases were unaffected. 7. On the basis of the electrical stimulation data and the properties revealed by the movement field analysis, we conclude that the collicular motor map is two dimensional. The reversible inactivation results suggest that the SC is not the site where three-dimensional fast phases of vestibular nystagmus are generated.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗