Occlusion Of Vision Research Articles

Exploring the Benefits of Stroboscopic Technology and Guided Visualization in Teaching Suturing Techniques to Veterinary Medicine Students.

Suturing is widely regarded to be a core competency of veterinary education. With curricular requirements expanding, training interventions that improve students' suturing skills without added time would be valuable. This study evaluated the effects of stroboscopic visual resistance training, a technique using intermittent occlusion of vision, and guided visualization on suturing technique and speed. Students' anxiety levels were also assessed. Twenty-nine veterinary students with no prior surgical experience were divided into stroboscopic, visualization and control groups. Simple interrupted, simple continuous, and cruciate patterns were taught by an American College of Veterinary Surgeons (ACVS)-boarded veterinarian in week 1, and students also took an anxiety test at this time. One-hour-long tutored practice sessions were held for each group in weeks 2, 3, 4 and 6, and assessments were conducted in weeks 5 and 7. Assessments were conducted by a second ACVS-boarded veterinarian blinded to group assignments. Students in the stroboscopic training group had faster suturing times compared to students in the control group for the cruciate pattern at week 5 (p = 0.001) and week 7 (p = 0.006), and faster times compared to students in the visualization group at week 5 (p = 0.002). Students in the stroboscopic training group had faster suturing times than the control group (p = 0.005) for the simple continuous pattern at week 7. No significant differences were observed in anxiety. There was no significant difference in technique scores for any group with any pattern at any time point. Stroboscopic training may result in faster suturing times without deterioration of suturing technique.

Rapid plasticity of visually evoked responses in rat monocular visual cortex.

Sensory cortical circuits are shaped by experience during sensitive periods in development. In the primary visual cortex (V1) altered visual experience results in changes in visual responsiveness of cortical neurons. The experience-dependent refinement of the circuit in V1 is thought to rely on competitive interactions between feedforward circuits driven by the two eyes. However, recent data have provided evidence for an additional role of cortico-cortical circuits in this process. Indeed, experience-dependent changes in intracortical circuits can be induced rapidly and may result in rapid-onset functional changes. Unilateral occlusion of vision rapidly alters visual responsiveness, synaptic strength and connectivity of local circuits in the binocular region of V1 (V1b), where the inputs from the two eyes converge. In the monocular region of rodent V1 (V1m), where feedforward inputs from the ipsilateral eye are virtually absent, visual deprivation induces rapid plasticity in local circuits; however, functional changes seem to occur only after long periods of deprivation. In V1m there is currently no evidence for functional changes occurring within a time window compatible with that of local circuit plasticity. Here, we probed the visual responsiveness of neurons in rat V1m and assessed the effect of one day unilateral eye lid suture on single neuron visual responses. We report a novel form of plasticity within V1m that occurs on a timescale consistent with the earliest known changes in synaptic strength. Our data provide new insights into how sensory experience can rapidly modulate neuronal responses, even in the absence of direct competition between feedforward thalamocortical inputs.

Homeostatic plasticity mechanisms in mouse V1.

Mechanisms thought of as homeostatic must exist to maintain neuronal activity in the brain within the dynamic range in which neurons can signal. Several distinct mechanisms have been demonstrated experimentally. Three mechanisms that act to restore levels of activity in the primary visual cortex of mice after occlusion and restoration of vision in one eye, which give rise to the phenomenon of ocular dominance plasticity, are discussed. The existence of different mechanisms raises the issue of how these mechanisms operate together to converge on the same set points of activity.This article is part of the themed issue 'Integrating Hebbian and homeostatic plasticity'.

An occlusion paradigm to assess the importance of the timing of the quiet eye fixation

The aim of the study was to explore the significance of the ‘timing’ of the quiet eye (QE), and the relative importance of late (online control) or early (pre-programming) visual information for accuracy. Twenty-seven skilled golfers completed a putting task using an occlusion paradigm with three conditions: early (prior to backswing), late (during putter stroke), and no (control) occlusion of vision. Performance, QE, and kinematic variables relating to the swing were measured. Results revealed that providing only early visual information (occluding late visual information) had a significant detrimental effect on performance and kinematic measures, compared to the control condition (no occlusion), despite QE durations being maintained. Conversely, providing only late visual information (occluding early visual information) was not significantly detrimental to performance or kinematics, with results similar to those in the control condition. These findings imply that the visual information extracted during movement execution – the late proportion of the QE – is critical when golf putting. The results challenge the predominant view that the QE serves only a pre-programming function. We propose that the different proportions of the QE (before and during movement) may serve different functions in supporting accuracy in golf putting.

Endovascular treatment of ophthalmic artery aneurysms: assessing balloon test occlusion and preservation of vision in coil embolization.

ICA-ophthalmic artery aneurysms have unique configurations corresponding to relative risks of ophthalmologic morbidities. Presented herein are clinical and radiologic outcomes of coil embolization in ophthalmic artery aneurysms. From January 2003 to September 2013, endovascular coiling was performed in 43 consecutive patients with ophthalmic artery aneurysms, each classified by the degree to which the ophthalmic artery was incorporated by the aneurysm and the contiguity between the ophthalmic artery entry and parent ICA. Clinical and radiologic outcomes of this approach were investigated, including the technical aspects of treatment and the efficacy of balloon test occlusion. Among 14 patients (32.6%, all ophthalmic artery types) undergoing balloon test occlusion before endovascular coiling, patent collaterals between the external carotid artery and ophthalmic artery were demonstrated in 12 (85.7%) and complete compromise of the ophthalmic artery (without affecting vision) occurred in 4 patients during coiling. Steam-shaped S-configured (67.9%) or straight microcatheters (17.8%) facilitated aneurysm selection in most of the superiorly directed ophthalmic artery aneurysms (n = 28), and steam-shaped pigtail microcatheters (85.7%) were useful in medially directed aneurysms (n = 14). Balloon protection (n = 22) was generally used to facilitate coiling, or a stent (n = 9) was alternatively deployed. Satisfactory aneurysmal occlusion was achieved through coil embolization in 37 lesions (86.1%). During follow-up of 35 patients (mean interval, 12.9 ± 9.4 months), only 1 instance (2.9%) of major recanalization was observed. If one tailors technical strategies, ophthalmic artery aneurysms are amenable to safe and effective endovascular coil embolization, which tends to be stable in follow-up. Balloon test occlusion may be helpful in devising treatment strategies to preserve vision when coiling ophthalmic artery aneurysms (especially those incorporating an ophthalmic artery origin) is done.

Acute Adult Onset Comitant Esotropia Associated with Accommodative Spasm

Acute onset comitant esotropia associated with spasm of accommodation in children and adults is a rare clinical condition. When occurring with pupillary miosis and restricted ocular motility, it is referred to as "spasm of near reflex" (SNR) and may require neurological investigation. The natural history of SNR depends on its etiology. There is little information in the literature regarding the long-term follow-up of SNR and the stability of visual signs and symptoms following cessation of treatment. We report a case of SNR in an otherwise healthy young male, and discuss the presentation, clinical investigations, management, response to treatment, and 1-year follow-up. A 23-year-old male patient reported to the clinic with sudden onset of blurred vision, inward deviation of the eyes, and binocular diplopia. On examination, he was diagnosed to have acute onset esotropia resulting from SNR. He was treated with cycloplegic medications and vision therapy. The condition resolved following 1 year and there has been no recurrence. Acute adult onset esotropia occurring with accommodative spasm responds favorably to cycloplegic medications but may need a longer course of treatment for successful resolution and stability.

Active Vision: Adapting How to Look

A new study has found that artificial occlusion of central vision leads to rapid emergence, and long-term maintenance of a new preferred retinal locus of fixation. These findings have important implications for the understanding of visual and oculomotor plasticity as well as for the development of rehabilitation techniques.

Effects of spatial-memory decay and dual-task interference on perturbation-evoked reach-to-grasp reactions in the absence of online visual feedback

Recent findings suggest that rapid perturbation-evoked reach-to-grasp balance-recovery reactions can be (and often are) guided by visuospatial information stored in working memory. To further our understanding, the present study examined the influence of memory-decay and concurrent cognitive-task performance on the speed, accuracy and effectiveness of these reactions by using liquid-crystal goggles to initiate occlusion of vision at various “recall-delay” times prior to perturbation-onset, in ten healthy young-adults. A small handhold was moved unpredictably to one of four locations 2s prior to vision-occlusion; reactions to recover balance by grasping the handhold were evoked by unpredictable antero-posterior platform-translation perturbations. Recall-delay time (0s/2s/5s/10s) was randomized, and subjects performed a spatial- or non-spatial-memory task during the delay-time in a subset of trials. Consistent with studies of volitional reach-to-grasp, recall-delay led to some reduction in endpoint accuracy; however, unlike those studies, the present results showed no evidence that recall-delay led to slowing of the arm movement. Both spatial and non-spatial cognitive tasks had similar effects (slowing of movement initiation and execution), suggesting these effects were related to generic attentional demands rather than competition for specific resources related to spatial working memory. Further work is needed to determine effects of age-related impairments in visuospatial memory and attentional capacity.

Center of pressure trajectories, trunk kinematics and trunk muscle activation during unstable sitting in low back pain patients

Trunk motor behavior has been reported to be altered in low-back pain. This may be associated with impaired lumbar proprioception, which could be compensated by trunk stiffening. We assessed trunk control by measuring center-of-pressure, lumbar kinematics and trunk muscle electromyography in 20 low-back pain patients and 11 healthy individuals during a seated balancing task, in conditions with and without disturbance of lumbar proprioception and occlusion of vision. We hypothesized that low-back pain patients show larger postural sway, but smaller thoraco-lumbar movements than healthy individuals. Repeated measures analyses of variance indicated that the effects of proprioception disturbance and vision occlusion were similar between groups. Interestingly, low-back pain patients grabbed the safety rail more often, while differences between groups in sway measures were rather subtle. This suggests that low-back pain patients were more cautious. Furthermore, low-back pain patients had an about 20 degrees less flexed lumbar posture than healthy individuals, and, in contrast to our hypothesis, made larger thoraco-lumbar movements in the sagittal plane, as indicated by higher SDs of thoraco-lumbar flexion and lower (more negative) correlations between pelvis and thorax movements. Activation of the intersegmental longissimus relative to the iliocostalis muscle, which spans all lumbar segments, was lower in low-back pain patients compared to healthy individuals. This difference in muscle activation may be causal for larger thoraco-lumbar movements, and may be causative of reduced control over segmental lumbar movement, but may also reflect the need for larger corrective movements to compensate balance impairments.

Like Windows in the Wall: Four Documentaries by Israeli Women

Within the frame of feminist theory, this paper analyzes the efforts of two Israeli filmmakers to disclose women's perceptual struggle: against gendered imperatives that encourage women not to look; against the habit of looking at "others" as objects to be feared or controlled; against the forces of materialism, national insecurity and political/military power that make looking impossible. In The Women Next Door and Detained , Michal Aviad and Anat Even interview Arab and Jewish women, enacting the transgressive intention to occupy what Kaja Silverman has called "a viewing position other than that assigned" by their culture. In Ever Shot Anyone? Aviad interviews male reservists, making visible the gendered imperative not to look—even as she defies it. And in Closure Even constructs a metaphor for the gradual occlusion of vision that constricts awareness of others and changes the promising trajectory of Israeli culture.

Abstract 17956: Serpin Treatment Reduces Inflammation in Transplanted Temporal Artery Biopsy Specimens from Patients with Suspected Giant Cell Arteritis in Immunodeficient Mice

Background - Giant cell / temporal arteritis (GCTA) is a severe inflammatory vasculitic syndrome (IVS), which causes arterial occlusion and sudden loss of vision. Treatment for IVS remains limited. Intra-aortic full thickness implants of human TA biopsy and left internal mammary artery (LIMA) specimens were surgically engrafted into the abdominal aorta of immunodeficient SCID mice as a new model for analyzing development of vascular inflammation, as well as response to new treatments. Serp-1 is a myxomaviral-derived serine protease inhibitor (serpin) that blocks thrombotic and thrombolytic protease pathways, arterial inflammation, and plaque growth. Serp-1 was recently tested in acute coronary syndromes (ACS), where reduced markers of myocardial damage were detected after stent implant. Objective - We assessed the effects of Serp-1 or saline treatment on inflammatory cell invasion and plaque growth after TA and LIMA engraftment in NOD-SCID mice. Results - Normal arterial (LIMA) specimens were harvested during bypass surgery and implanted into 24 SCID mice. Half the mice had saline (N=12) and half had Serp-1 treatment (N=12). In each group 6 mice had 5x106 peripheral blood mononuclear cells (PBMCs) infusions from the same patient as the donor LIMA graft, given immediately postop by tail vein and 6 had no cell infusion. TA grafts from patients with suspected GCA were implanted into a separate group of 24 SCID mice - 12 mice had saline (100µl) and 12 Serp-1 (100ng/g/100µl) treatment (one i.v. injection followed by daily i.p. injection for 10 days). in each treatment group 4 mice had infusion of non-matched PBMCs. At 4 weeks LIMA (P < 0.034) or TA (P < 0.0001) grafts, had significantly reduced plaque growth with Serp-1 treatment when human PBMC were also infused (p<0.05). In the absence of PBMC, Serp-1 had minimal effect. Mononuclear cell invasion was reduced in Serp-1 treated mice with PBMCs. Flow cytometry did not detect significant changes in splenocytes. Conclusions - Aortic implant of human LIMA or TA xenografts in SCID mice provides a physiological model for investigating inflammatory vasculitis. With PBMC infusion, treatment with the myxomaviral Serp-1, reduced inflammatory cell invasion and plaque growth in arterial xenografts.

An event-related visual occlusion method for examining anticipatory skill in natural interceptive tasks

This article describes a new automated method for the controlled occlusion of vision during natural tasks. The method permits the time course of the presence or absence of visual information to be linked to identifiable events within the task of interest. An example application is presented in which the method is used to examine the ability of cricket batsmen to pick up useful information from the prerelease movement patterns of the opposing bowler. Two key events, separated by a consistent within-action time lag, were identified in the cricket bowling action sequence-namely, the penultimate foot strike prior to ball release (Event 1), and the subsequent moment of ball release (Event 2). Force-plate registration of Event 1 was then used as a trigger to facilitate automated occlusion of vision using liquid crystal occlusion goggles at time points relative to Event 2. Validation demonstrated that, compared with existing approaches that are based on manual triggering, this method of occlusion permitted considerable gains in temporal precision and a reduction in the number of unusable trials. A more efficient and accurate protocol to examine anticipation is produced, while preserving the important natural coupling between perception and action.

Visuomotor control of step descent: evidence of specialised role of the lower visual field

We often complete step downs in the absence of visual feedback of the lower-limbs, and/or of the area on the ground where we intend to land (e.g. when descending a step whilst carrying a laundry basket). Therefore, the present study examined whether information from lower visual field (lvf) provides any advantage to the control of step descent. Ten healthy subjects (age 24.4 +/- 9.4 years) completed repeated step downs over three-step heights with visual information available from either full or upper visual fields (lvf occluded), and for specific intervals relative to step initiation. Visuomotor control of step descent was assessed by determining pre-landing kinematic measures and landing mechanic variables for the initial landing period. Findings indicate that whilst there were only limited effects on pre-landing kinematic measures under lvf occlusion, individual's ability to plan/control landing mechanics was significantly different in such conditions compared to when they had access to full field vision. These changes were consistent with participants being uncertain regarding precise floor height when access to lvf was restricted, and consequently led them to adapt their landing behaviour but without fundamentally altering their stepping strategy. Compared to when vision was available throughout, the occlusion of vision (full or upper visual field) from toe-off or mid-swing onwards caused very few differences in landing behaviour. This suggests that the contribution of information from lvf to the control of landing behaviour occurs predominantly prior to or during movement initiation and that 'online' vision is used only in the latter portion of the descent phase to subtly 'fine tune' landings.

Mystery of Environmental Mystery

The purpose of this article is to estimate the strengths of the relationships between judgments of mystery and amount of light, depth of view, and occlusion, whether visual and locomotive occlusion or just visual occlusion. Three experiments were conducted with totals of 145 respondents and 33 scenes. Light had the largest effect on mystery, followed by occlusion of both vision and locomotion and occlusion only of locomotion. Mystery might be a function of vision, not of locomotion. Overall, depth of view had a very small effect on mystery, but effect of depth on mystery was higher at shorter ranges than at longer ranges, suggesting that distance from observer to occluding boundary might be an influential covariate in environmental mystery.

Visual-vestibular influences on locomotor adjustments for stepping over an obstacle

Combined visual and vestibular influences on locomotor control, particularly in changing environments, are little understood. We studied such influences on body orientation and foot trajectory control during level walking and obstacle avoidance. Six young adults walked on the level and over an obstacle while vision was present or occluded as well as while vestibular information was intact or perturbed using galvanic vestibular stimulation (GVS). The occlusion of vision caused a slowing of gait during obstacle avoidance as well as increased clearance of the leading limb over the obstruction. GVS caused lateral deviations in head and trunk roll angles as well as in foot and trunk displacements, but these lateral deviations were the same during both level walking and obstacle avoidance. In addition, GVS had no effect at all on sagittal plane factors such as speed, foot proximity to the obstacle and vertical clearance over the obstacle. Overall, there is a complex visual control of bilateral obstacle avoidance, but the lack of differences in GVS effects between level and obstructed walking shows that vestibular information is not upregulated for obstacle avoidance. In addition, the robust indifference of anterior foot placement and body displacement to significant lateral deviations from GVS suggests an orthogonally based sensori-locomotor control.

Initiation of rapid reach-and-grasp balance reactions: is a pre-formed visuospatial map used in controlling the initial arm trajectory?

In order to recover balance by grasping an object for support, the CNS must rapidly move the hand toward a specific target (handhold) in the environment. The early latency (80-140 ms) of these grasping reactions would seem to preclude a role for online visual feedback in the control of the initial limb movement; however, some studies have shown that vision can influence initiation of lower-limb postural reactions at similar latency. This study explored the role of vision in controlling the initial trajectory of grasping reactions triggered by sudden unpredictable medio-lateral platform translation. Healthy young adults were instructed to recover balance by grasping a marked section of a handrail, located to their right. To reinforce a dependence on arm reactions, movement of the feet was prevented by barriers. Liquid-crystal goggles were used to occlude vision during response initiation (200 ms interval starting at perturbation onset, PO). Results showed that the initial grasping trajectory (first 100 ms) and associated muscle activation were heavily modulated to take into account the direction and speed of the perturbation-induced body motion in relation to the handrail. This modulation was unaffected by occlusion of vision at PO, indicating that information about the rail location obtained prior to PO was incorporated into the control. These findings are consistent with the view that the CNS tunes the initial arm trajectory by combining an egocentric spatial map, formed prior to PO, with online feedback about the body motion from non-visual inputs (somatosensory and/or vestibular). This prevents potential delays associated with visual processing and ensures very rapid onset of arm movement that is directed appropriately even though the position of the body is perturbed unpredictably with respect to the target.

Neurobiology of Memory

Back to table of contents Previous article Next article Classic ArticlesFull AccessNeurobiology of MemoryThomas C. Neylan, M.D., Section EditorThomas C. NeylanSearch for more papers by this author, M.D., Section EditorPublished Online:1 May 2001AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail Eric Kandel's “Psychotherapy and the Single Synapse,” reprinted here, is an elegant and inspirational essay on the relationship of clinical psychiatry to cellular biology. It examines how psychology and psychiatry as clinical fields frame the broad conceptual questions that ideally direct the focus of molecular and cellular neurobiology. Dr. Kandel's article draws attention to two prominent paradigms demonstrating how advances in basic neuroscience were led by clinical observations—a line of investigation currently referred to as “translational research.”The first paradigm highlighted in the article pertains to the observed effects of adverse early developmental experiences on brain development. Dr. Kandel cites the seminal work of Hubel and Wiesel, who showed in a number of studies that monocular occlusion of vision in newborn animals led to permanent abnormalities in the visual cortex. Hence, these studies dramatically demonstrated that sensory input has a crucial role in the development and organization of the brain.The second paradigm pertains to two aspects of learning: habituation and sensitization. Dr. Kandel presents his own work on a simple animal model of learning, the gill reflex of the marine slug Aplysia californica. Dr. Kandel has made astonishing discoveries in how changes in synaptic structure and efficacy are associated with learning. He concludes that all experiential events, including psychotherapeutic interventions, ultimately affect the structure and function of neuronal synapses.What is particularly striking about the choice of the two paradigms made by Dr. Kandel in this 1979 article is that accomplishments in both of these areas were subsequently recognized by the Nobel Assembly with the highest award given in our field. Hubel and Wiesel were awarded the Nobel Prize in Medicine or Physiology in 1981, and Dr. Kandel shared the same prize with Arvid Carlsson and Paul Greengard in 2000. FiguresReferencesCited byDetailsCited byNone Volume 13Issue 2 May 2001Pages 289-289 Metrics PDF download History Published online 1 May 2001 Published in print 1 May 2001

Neurobiology of Memory

Back to table of contents Previous article Next article Classic ArticlesFull AccessNeurobiology of MemoryThomas C. Neylan, M.D., Section EditorThomas C. NeylanSearch for more papers by this author, M.D., Section EditorPublished Online:1 May 2001AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail Eric Kandel's “Psychotherapy and the Single Synapse,” reprinted here, is an elegant and inspirational essay on the relationship of clinical psychiatry to cellular biology. It examines how psychology and psychiatry as clinical fields frame the broad conceptual questions that ideally direct the focus of molecular and cellular neurobiology. Dr. Kandel's article draws attention to two prominent paradigms demonstrating how advances in basic neuroscience were led by clinical observations—a line of investigation currently referred to as “translational research.”The first paradigm highlighted in the article pertains to the observed effects of adverse early developmental experiences on brain development. Dr. Kandel cites the seminal work of Hubel and Wiesel, who showed in a number of studies that monocular occlusion of vision in newborn animals led to permanent abnormalities in the visual cortex. Hence, these studies dramatically demonstrated that sensory input has a crucial role in the development and organization of the brain.The second paradigm pertains to two aspects of learning: habituation and sensitization. Dr. Kandel presents his own work on a simple animal model of learning, the gill reflex of the marine slug Aplysia californica. Dr. Kandel has made astonishing discoveries in how changes in synaptic structure and efficacy are associated with learning. He concludes that all experiential events, including psychotherapeutic interventions, ultimately affect the structure and function of neuronal synapses.What is particularly striking about the choice of the two paradigms made by Dr. Kandel in this 1979 article is that accomplishments in both of these areas were subsequently recognized by the Nobel Assembly with the highest award given in our field. Hubel and Wiesel were awarded the Nobel Prize in Medicine or Physiology in 1981, and Dr. Kandel shared the same prize with Arvid Carlsson and Paul Greengard in 2000. FiguresReferencesCited byDetailsCited ByNone Volume 13Issue 2 May 2001Pages 289-289 Metrics PDF download History Published online 1 May 2001 Published in print 1 May 2001

Practical hints when fitting tinted contact lenses for vision occlusion

In some cases a tinted contact lens is clinically necessary for a patient to obtain occlusion of vision. Indications include intractable diplopia and confusing image distortions resulting from retinal trauma. This paper gives guidelines on contact lens fitting in such cases and describes the difficulties encountered in achieving a balance between adequate occlusion and cosmetic appearance. The importance of patient counselling is emphasised.

Deficient Plasticity in the Primary Visual Cortex of α-Calcium/Calmodulin-Dependent Protein Kinase II Mutant Mice

The recent characterization of plasticity in the mouse visual cortex permits the use of mutant mice to investigate the cellular mechanisms underlying activity-dependent development. As calcium-dependent signaling pathways have been implicated in neuronal plasticity, we examined visual cortical plasticity in mice lacking the α-isoform of calcium/calmodulin-dependent protein kinase II (αCaMKII). In wild-type mice, brief occlusion of vision in one eye during a critical period reduces responses in the visual cortex. In half of the αCaMKII-deficient mice, visual cortical responses developed normally, but visual cortical plasticity was greatly diminished. After intensive training, spatial learning in the Morris water maze was severely impaired in a similar fraction of mutant animals. These data indicate that loss of αCaMKII results in a severe but variable defect in neuronal plasticity.