Role Of Eye Movements Research Articles

The role of eye movements in bistability from perceptual and binocular rivalry and the role of voluntary control

The role of eye movements in bistability from perceptual and binocular rivalry and the role of voluntary control

Palisade endings in extraocular eye muscles revealed by SNAP-25 immunoreactivity.

Palisade endings form a cuff of nerve terminals around the tip of muscle fibres. They are found only in extraocular muscles, but no definite evidence for their role in eye movements has been established. Palisade endings have been reported in all species so far investigated except the rat. In this study we demonstrate that antibodies against SNAP-25, the synaptosomal associated protein of 25 kDa, reliably visualize the complete motor, sensory and autonomic innervation of the extraocular muscles in human, monkey and rat. The SNAP-25 antibody can be combined with other immunofluorescence procedures, and is used here to study properties of palisade endings. With SNAP-25 immunolabelling putative palisade endings are identified in the rat for the first time. They are not well branched, but fulfil several criteria of palisade endings, being associated with non-twitch fibres as shown by double labelling with 'myosin heavy chain slow-twitch' antibodies. The putative palisade endings of the rat lack alpha-bungarotoxin binding, which implies that these synapses are sensory. If palisade endings are sensory then they could function as an eye muscle proprioceptor. They seem to be a general feature of all vertebrate eye muscles, unlike the other two extraocular proprioceptors, muscle spindles and Golgi tendon organs, the presence of which varies widely between species.

Cavernous sinus and its role in eye movements and eye health

The cavernous sinuses are relatively large in lower animals probably because their function is more pronounced. The eye movements in these animals are not only essential in the provision of binocular vision, but also essential in protection of their lives. For example, when the deer runs and the tiger is running behind in an attempt to catch it, the deer is able to see not only ahead, but can also see the chasing tiger at the same time. This is due to the wide range and rapidity of its eye movements. The cavernous sinuses in the fish are relatively much large in size. The eye movements in the fish not only assist in provision of a wide range of visual field, but are also essential in providing balance whilst swimming. Absence of vision in one eye is not compatible with life in most fishes. The range of eyeball movements and its possible functions in a human are limited and that may be the possible reason of the cavernous sinus being relatively small in size. The cavernous sinuses drain the entire venous blood of the orbit. Their relative capaciousness, ability to stretch and their interconnectedness are essential elements on which the hydrodynamics of the fluid filled anterior and posterior chambers of the eyeball thrive. The fluid turnover in both the chambers has to be rapid, fairly constant and at highly controlled pressure. A single cavernous sinus provides a large efferent area into which the orbit can quickly drain any excess blood. As a further backup, one cavernous sinus is connected to another to provide yet more area. The sinusoidal dilatation of the venous circuitry in the region of the cavernous sinus appears to be necessary for the performance of the function of a sponge or a shock absorber of the eyeball. The pathos of the eye when the cavernous sinuses are thrombosed speaks for the significant role that they play during physiological states. All eye movements are lost despite functioning and anatomically intact cranial nerves. In severe cavernous sinus thrombosis, the venous drainage from the eye ball can be hampered, and there can be severe rise in intraocular pressure and even blindness. The eye movements and function return to normal when the blood flow within the venous spaces of the cavernous sinus is restored. It appears that the veins participate in all the movements of the eyeball by constant drainage and blood pooling. The intercavernous sinuses probably assist in coordinating movements of both the eyes. When an external pressure is applied on the eyeball, the venous spaces behind the eyeball and the cavernous sinuses protect the eyeball by providing a buffer space, a situation simulating the buffer provided by cerebrospinal fluid in the brain. The rapid drainage that the cavernous sinuses provide protect the delicate retinal artery, which is devoid of muscularis layer, from raised pressure and consequent rupture due to the venous congestion.

Vision Restoration Therapy (VRT) for the treatment of visual field deficits after brain damage: the role of eye movements and fixation behavior

Vision Restoration Therapy (VRT) for the treatment of visual field deficits after brain damage: the role of eye movements and fixation behavior

The Duncker illusion: intersubject variability, brief exposure, and the role of eye movements in its generation.

The Duncker illusion, also known as induced motion, is the illusory component of an object's motion that results from background movement. The origins of this robust phenomenon are still subject to debate. The goal of this study was to examine the role eye movements play in its generation. The Duncker illusion was generated by rear-projecting an LED target and a random-dot background onto a semitranslucent screen. Each moved under independent control of mirror galvanometers. The background was either stationary or moved vertically, whereas the target moved horizontally with various degrees of a vertical component. Using a two-alternative, forced-choice cancellation paradigm involving multiple interleaved staircases, seven human subjects quantified the illusion under a variety of conditions. These conditions included varying the exposure time from 50 to 200 ms. The strength of the illusion did not decrease, even when exposures too brief to generate eye movement were used. Four of the subjects showed no difference between long and short exposures (P > 0.12). In two the illusion was stronger for short exposures (P < 0.05), and in one the illusion was not quantifiable. There was little intrasubject variability across trial types, yet there was a large intersubject variability in the strength of the illusion. The illusion is robust in that it is perceived under a wide variety of conditions by all observers. By varying the parameters, it was possible to demonstrate that eye movements do not play a role in generating the illusion and that this robust illusion is most likely caused by the visual system attributing relative motion between target and background to target motion and ignoring any true background movement. The mechanism by which this occurs varies in degree between individuals.

Perceived localizations and eye movements with action‐generated and computer‐generated vanishing points of moving stimuli

When observers localize the vanishing point of a moving target, localizations are reliably displaced beyond the final position, in the direction the stimulus was travelling just prior to its offset. We examined modulations of this phenomenon through eye movements and action control over the vanishing point. In Experiment 1 with pursuit eye movements, localization errors were in movement direction, but less pronounced when the vanishing point was self‐determined by a key press of the observer. In contrast, in Experiment 2 with fixation instruction, localization errors were opposite movement direction and independent from action control. This pattern of results points at the role of eye movements, which were gathered in Experiment 3. That experiment showed that the eyes lagged behind the target at the point in time, when it vanished from the screen, but that the eyes continued to drift on the targets' virtual trajectory. It is suggested that the perceived target position resulted from the spatial lag of the eyes and of the persisting retinal image during the drift.

Clinical Implications and Recommendations Arising from EMDR Research Findings

ABSTRACT Eye movement desensitization and reprocessing (EMDR) is a treatment approach found to be efficacious for trauma-related disorders. This article provides an overview of the EMDR treatment process and briefly describes treatment components. It reviews the current research investigating EMDR treatment of posttraumatic stress disorder and research investigating the role of eye movements. The practical clinical implications arising from the findings are discussed. These include factors related to treatment provision, such as treatment fidelity, length of treatment, homework, and the use of eye movements. Also highlighted are client-related factors such as population, type of trauma, multiple traumas, symptom severity, comorbid disorders, and complex PTSD. Where possible, recommendations are made for clinical practice and comparisons are made with other types of treatments.

The role of eye movements in perception

For Gibson, sensory stimulation is neither the cause nor a component of perception, but merely incidental. Perception is based on the pickup of information, which occurs when purposeful observers actively seek information. I present a case in which only with the active sampling of the ambient optical flow field can observers extract the requisite information for the control of locomotion.

Identification of visual stimuli is improved by accompanying auditory stimuli: the role of eye movements and sound location.

Can auditory signals influence the processing of visual information? The present study examined the effects of simple auditory signals (clicks and noise bursts) whose onset was simultaneous with that of the visual target, but which provided no information about the target. It was found that such a signal enhances performance in the visual task: the accessory sound reduced response times for target identification with no cost to accuracy. The spatial location of the sound (whether central to the display or at the target location) did not modify this facilitation. Furthermore, the same pattern of facilitation was evident whether the observer fixated centrally or moved their eyes to the target. The results were not altered by changes in the contrast (and therefore visibility) of the visual stimulus or by the perceived utility of the spatial location of the sound. We speculate that the auditory signal may promote attentional 'disengagement' and that, as a result, observers are able to process the visual target sooner when sound accompanies the display relative to when visual information is presented alone.

Locating regions-of-interest for the Mars Rover expedition

In this paper, we demonstrate that image processing algorithms (IPAs) can perform a new visual task, namely, selecting and locating regions-of-interest (ROIs). This task has been defined on the basis of a theory of human vision: the scanpath theory. Further, using the measures Sp and Ss, the similarity of location and ordering, respectively, developed over the years in studying human perception and the active looking role of eye movements, we could quantify the efficient and efficacious manner by which IPAs can imitate human vision in locating ROIs. The methodology in this paper is applied to the Mars Rover exploration.

The current status of eye movement desensitization and reprocessing (EMDR)

Eye movement desensitization and reprocessing therapy (EMDR) has increasingly been proposed as an effective therapeutic procedure for post-traumatic stress disorder and other mental health problems. However, views on EMDR in the research literature have been polarized. Reasons for this are explored as is the nature and theoretical basis of EMDR. Fifteen controlled studies thus far published on EMDR and PTSD are reviewed, and it is concluded that (i) EMDR is an effective psychotherapy, (ii) EMDR's relative efficacy in comparison to behavioural exposure therapies has yet to be established, (iii) the role of eye movements and laterality in attentional focus remains controversial and (iv) a direct link between the theoretical basis of the therapy and observable psychological and neurobiological changes has yet to be established. Copyright © 1999 John Wiley & Sons, Ltd.

Oculographic Assessment of Workload Influence on Flight Performance

Presented are specific parameters of visual information intake in pilots on the job. The role of eye movements in the process of visual stimulus reception is discussed. Our own study on a MIG-23 flight simulator is presented. The method of oculographic testing of pilots performing professional assignments differing in workload is presented, and the practical implications of oculographic research are discussed.

Efficacy of eye movement desensitization and reprocessing: Implications for behavior therapy

The commitment of behavior therapy to empiricism has led it to a prominent position in the development of validated methods of treatment. The recent development and rapid expansion of Eye Movement Desensitization and Reprocessing (EMDR), a treatment that bears a resemblance to behavioral techniques and that has been proposed as an alternative to such techniques for numerous psychological disorders, raises important questions for the field of behavior therapy. In this article, we examine 17 recent studies on the effectiveness of EMDR and the conceptual analysis of its mechanisms of action. The research we review shows that (a) the effects of EMDR are limited largely or entirely to verbal report indices, (b) eye movements appear to be unnecessary for improvement, and (c) reported effects are consistent with non-specific procedural artifacts. Moreover, the conceptual analysis of EMDR is inconsistent with scientific findings concerning the role of eye movements. Implications of the empirical and theoretical literature on EMDR for behavior therapy are discussed.

Calcitonin gene-related peptide immunoreactivity selectively labels accessory optic nuclei and pathways of the rat visual system.

The present study shows the distribution of calcitonin gene-related peptide (CGRP)-immunolabeled neuronal somata and fibers in the accessory optic system of adult rats. CGRP-immunoreactive cell bodies were small to medium-sized and mostly fusiform or oval-shaped. Both immunolabeled somata and fibers were found in the dorsal and lateral terminal nuclei as well as in the interstitial nucleus of the superior fasciculus (posterior fibers); whereas only immunoreactive fibers were found in the ventral division of the medial terminal nucleus, particularly its rostral portion. These results indicate that CGRP-containing neurons are present in all nuclear components of the accessory optic system and suggest that this neuropeptide may play a neuromodulative role in eye movements.

A correlation procedure for the single-sweep analysis of event-related potentials

There has been considerable focus placed on how individuals with autism spectrum disorder (ASD) visually perceive and attend to social information, such as facial expressions or social gaze. The role of eye movements is inextricable from visual perception, however this aspect is often overlooked. We performed a series of meta-analyses based on data from 28 studies of eye movements in ASD to determine whether there is evidence for ocular motor dysfunction in ASD. Tasks assessed included visually-guided saccade tasks, gap/overlap, anti-saccade, pursuit tasks and ocular fixation. These analyses revealed evidence for ocular motor dysfunction in ASD, specifically relating to saccade dysmetria, difficulty inhibiting saccades and impaired tracking of moving targets. However there was no evidence for deficits relating to initiating eye movements, or engaging and disengaging from simple visual targets. Characterizing ocular motor abnormalities in ASD may provide insight into the functional integrity of brain networks in ASD across development, and assist our understanding of visual and social attention in ASD.

Efferent pathways of the nucleus of the optic tract in monkey and their role in eye movements

To clarify the role of the pretectal nucleus of the optic tract (NOT) in ocular following, we traced NOT efferents with tritiated leucine in the monkey and identified the cell groups they targeted. Strong local projections from the NOT were demonstrated to the superior colliculus and the dorsal terminal nucleus bilaterally and to the contralateral NOT. The contralateral oculomotor complex, including motoneurons (C-group) and subdivisions of the Edinger-Westphal complex, including motoneurons (C-group) and subdivisions of the Edinger-Westphal complex, also received inputs. NOT efferents terminated in all accessory optic nuclei (AON) ipsilaterally; contralateral AON projections arose from the pretectal olivary nucleus embedded in the NOT. Descending pathways contacted precerebellar nuclei: the dorsolateral and dorsomedial pontine nuclei, the nucleus reticularis tegmenti pontis, and the inferior olive. Direct projections from NOT to the ipsilateral nucleus prepositus hypoglossi (ppH) appeared to be weak, but retrograde tracer injections into rostral ppH verified this projection; furthermore, the injections demonstrated that AON efferents also enter this area. Efferents from the NOT also targeted ascending reticular networks from the pedunculopontine tegmental nucleus and the locus coeruleus. Rostrally, NOT projections included the magnocellular layers of the lateral geniculate nucleus (lgn); the pregeniculate, peripeduncular, and thalamic reticular nuclei; and the pulvinar, the zona incerta, the mesencephalic reticular formation, the intralaminar thalamic nuclei, and the hypothalamus. The NOT could generate optokinetic nystagmus through projections to the AON, the ppH, and the precerebellar nuclei. However, NOT also projects to structures controlling saccades, ocular pursuit, the near response, lgn motion sensitivity, visual attention, vigilance, and gain modification of the vestibulo-ocular reflex. Any hypothesis on the function of NOT must take into account its connectivity to all of these visuomotor structures.

Efferent pathways of the nucleus of the optic tract in monkey and their role in eye movements

Efferent pathways of the nucleus of the optic tract in monkey and their role in eye movements

Pretectal projections to the oculomotor complex of the monkey and their role in eye movements.

The nucleus of the optic tract (NOT) is associated with the generation of optokinetic nystagmus (OKN), whereas the olivary pretectal nucleus (ol), which lies embedded in the primate NOT, is believed to be essential for the pupillary light reflex. In this anatomical study of the pretectum, projections from NOT and ol to structures around the oculomotor nucleus were traced in the monkey, to determine which cell groups they innervated. 1. 3[H]-leucine injections were placed into NOT and ol, and labelled terminals were observed just outside the classical oculomotor nucleus (nIII), in the "C-group' and midline cell clusters, both of which contain small motoneurons of the extraocular eye muscles. In addition, there were strong projections to the lateral visceral cell column of the Edinger-Westphal complex (lvc), but not to the Edinger-Westphal nucleus (EW) itself. All of these projections were mainly contralateral. 2. NOT efferents terminated over the ipsilateral medial accessory nucleus of Bechterew (nB), but not over the adjacent nucleus Darkschewitsch. 3. Injections of a retrograde tracer into the oculomotor complex showed that the pretectal afferents described above originated mainly from the dorsomedial part of NOT and from ol. 4. The use of a transsynaptic retrograde tracer, tetanus toxin fragment (BIIb), established the monosynaptic nature of the connection between dorsomedial NOT (contralaterally) and ol (bilaterally), to the small extraocular motoneurons outside classical nIII. The "C-group' motoneurons may play a role in vergence, and lvc in pupillary constriction and depth of focus. Our results imply that NOT and ol participate in the control of some aspects of the near-response, which may be important in the generation of some components of OKN in primates.

Pretectal projections to the oculomotor complex of the monkey and their role in eye movements

Pretectal projections to the oculomotor complex of the monkey and their role in eye movements

The eccentricity effect: target eccentricity affects performance on conjunction searches.

The serial pattern found for conjunction visual-search tasks has been attributed to covert attentional shifts, even though the possible contributions of target location have not been considered. To investigate the effect of target location on orientation x color conjunction searches, the target's duration and its position in the display were manipulated. The display was present either until observers responded (Experiment 1), for 104 msec (Experiment 2), or for 62 msec (Experiment 3). Target eccentricity critically affected performance: A pronounced eccentricity effect was very similar for all three experiments; as eccentricity increased, reaction times and errors increased gradually. Furthermore, the set-size effect became more pronounced as target eccentricity increased, and the extent of the eccentricity effect increased for larger set sizes. In addition, according to stepwise regressions, target eccentricity as well as its interaction with set size were good predictors of performance. We suggest that these findings could be explained by spatial-resolution and lateral-inhibition factors. The serial self-terminating hypothesis for orientation x color conjunction searches was evaluated and rejected. We compared the eccentricity effect as well as the extent of the orientation asymmetry in these three conjunction experiments with those found in feature experiments (Carrasco & Katz, 1992). The roles of eye movements, spatial resolution, and covert attention in the eccentricity effect, as well as their implications, are discussed.