The authors are supported by an International Brain Research Foundation Postdoctoral Fellowship (DC); doctoral training grant T90 DA 022763 (MA); and NIH grant R01-EY017699 and NSF grant BCS-0633281 (SK). The authors are grateful to Randolph Blake for useful comments.

<ol><li>Blake, R., Logothetis, N. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Visual+competition%5BTitle%5D)+AND+%22Nat.+Rev.+Neurosci%22%5BJournal%5D)">Visual competition.</a> Nat. Rev. Neurosci. 3, 13-21 (2002).</li>
<li>Rees, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neuroimaging+of+visual+awareness+in+patients+and+normal+subjects%5BTitle%5D)+AND+%22Curr.+Op.+Neurobiol%22%5BJournal%5D)">Neuroimaging of visual awareness in patients and normal subjects.</a> Curr. Op. Neurobiol. 11, 150-156 (2001).</li>
<li>Bahrami, B., Carmel, D., Walsh, V., Rees, G., Lavie, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Unconscious+orientation+processing+depends+on+perceptual+load%5BTitle%5D)+AND+%22Journal+of+Vision%22%5BJournal%5D)">Unconscious orientation processing depends on perceptual load.</a> Journal of Vision. 8, 1-10 (2008).</li>
<li>Bahrami, B., Carmel, D., Walsh, V., Rees, G., Lavie, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Spatial+attention+can+modulate+unconscious+orientation+processing%5BTitle%5D)+AND+%22Perception%22%5BJournal%5D)">Spatial attention can modulate unconscious orientation processing.</a> Perception. 37, 1520-1528 (2008).</li>
<li>Carmel, D., Walsh, V., Lavie, N., Rees, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Right+parietal+TMS+shortens+dominance+durations+in+binocular+rivalry%5BTitle%5D)+AND+%22Current+Biology%22%5BJournal%5D)">Right parietal TMS shortens dominance durations in binocular rivalry.</a> Current Biology. , Forthcoming Forthcoming.</li>
<li>Schurger, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+very+inexpensive+MRI-compatible+method+for+dichoptic+visual+stimulation%5BTitle%5D)+AND+%22J.+Neurosci.+Methods%22%5BJournal%5D)">A very inexpensive MRI-compatible method for dichoptic visual stimulation.</a> J. Neurosci. Methods. 177, 199-202 (2009).</li>
<li>Tong, F., Nakayama, K., Vaughn, J. T., Kanwisher, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Binocular+rivalry+and+visual+awareness+in+human+extrastriate+cortex%5BTitle%5D)+AND+%22Neuron%22%5BJournal%5D)">Binocular rivalry and visual awareness in human extrastriate cortex.</a> Neuron. 21, 753-759 (1998).</li>
<li>Kovacs, I., Papathomas, T. V., Ming, Y., Feher, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((When+the+brain+changes+its+mind%3A+interocular+grouping+during+binocular+rivalry%5BTitle%5D)+AND+%22Proc.+Natl.+Acad.+Sci.+USA%22%5BJournal%5D)">When the brain changes its mind: interocular grouping during binocular rivalry.</a> Proc. Natl. Acad. Sci. USA. 93, 15508-15511 (1996).</li>
<li>Blake, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+primer+on+binocular+rivalry%2C+including+current+controversies%5BTitle%5D)+AND+%22Brain+and+Mind%22%5BJournal%5D)">A primer on binocular rivalry, including current controversies.</a> Brain and Mind. 2, 5-38 (2001).</li>
<li>Cowey, A., Stoerig, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+neurobiology+of+blindsight%5BTitle%5D)+AND+%22Trends+Neurosci%22%5BJournal%5D)">The neurobiology of blindsight.</a> Trends Neurosci. 14, 140-145 (1991).</li>
<li>Nasrallah, M., Carmel, D., Lavie, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Murder+she+wrote%3A+enhanced+sensitivity+to+negative+word+valence%5BTitle%5D)+AND+%22Emotion%22%5BJournal%5D)">Murder she wrote: enhanced sensitivity to negative word valence.</a> Emotion. 9, 609-618 (2009).</li>
<li>Persaud, N., McLeod, P., Cowey, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Post-decision+wagering+objectively+measures+awareness%5BTitle%5D)+AND+%22Nat+Neurosci%22%5BJournal%5D)">Post-decision wagering objectively measures awareness.</a> Nat Neurosci. 10, 257-261 (2007).</li>
<li>Tsuchiya, N., Koch, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Continuous+flash+suppression+reduces+negative+afterimages%5BTitle%5D)+AND+%22Nat.+Neurosci%22%5BJournal%5D)">Continuous flash suppression reduces negative afterimages.</a> Nat. Neurosci. 8, 1096-1101 (2005).</li>
<li>Bahrami, B., Lavie, N., Rees, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Attentional+Load+Modulates+Responses+of+Human+Primary+Visual+Cortex+to+Invisible+Stimuli%5BTitle%5D)+AND+%22Curr.+Biol%22%5BJournal%5D)">Attentional Load Modulates Responses of Human Primary Visual Cortex to Invisible Stimuli.</a> Curr. Biol. 17, 509-513 (2007).</li>
<li>Wilson, H. R., Blake, R., Lee, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Dynamics+of+travelling+waves+in+visual+perception%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Dynamics of travelling waves in visual perception.</a> Nature. 412, 907-910 (2001).</li>
<li>Meng, M., Tong, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Can+attention+selectively+bias+bistable+perception%3F+Differences+between+binocular+rivalry+and+ambiguous+figures%5BTitle%5D)+AND+%22Journal+of+Vision%22%5BJournal%5D)">Can attention selectively bias bistable perception? Differences between binocular rivalry and ambiguous figures.</a> Journal of Vision. 4, 539-551 (2004).</li>
</ol>

No conflicts of interest declared.

We have described the nature of binocular rivalry, several methods for creating it, and what considerations must be taken into account when it is used. As detailed in the Introduction, appropriate use of binocular rivalry makes it possible to experimentally address questions regarding the locus (or loci) of awareness, perceptual selection and unconscious processing. To carry out such investigations properly, however, one must be aware of issues such as the importance of maintaining stable vergence, and, if investigating unconscious processing, the necessity of using displays that are likely to yield complete suppression.
When choosing which method to use in order to create rivalry, it is important to take into account the advantages and disadvantages of each method. There is no point, for example, in using red-blue goggles if one is interested in using multi-colored stimuli; but on the other hand, this method is probably the easiest to use in an MRI scanner. Similarly, a mirror stereoscope is a very reliable way of ensuring that separate images fall on corresponding retinal locations; but the individual adjustments required for each observer and the technical difficulties involved in putting a stereoscope in an MRI scanner might make this method less attractive for some studies.
Finally, it is important to be aware of the characteristics of the experience of binocular rivalry in order to employ the appropriate dependent measures. When the research question concerns unconscious processing, independent verification that participants were indeed unaware of the suppressed image is essential. When one is interested in how an experimental manipulation affects dominance and suppression durations, it may be more illuminating to examine the (gamma-shaped) distribution of durations rather than just a central tendency measure such as the mean or median; and it may be important to ascertain whether the observers experienced sharp or gradual (piecemeal or wave-like) transitions of dominance.
We hope researchers interested in employing this fascinating phenomenon will find this introduction helpful.

<table><tbody><tr><td>Mirror stereoscope</td><td></td><td></td><td></td></tr><tr><td>Prism goggles</td><td></td><td></td><td></td></tr><tr><td>Red-blue or red-green cellophane goggles</td><td></td><td></td><td></td></tr><tr><td>Computer monitor (optional)</td><td></td><td></td><td></td></tr></tbody></table>

how to create and use binocular rivalry

Each of our eyes normally sees a slightly different image of the world around us. The brain can combine these two images into a single coherent representation. However, when the eyes are presented with images that are sufficiently different from each other, an interesting thing happens: Rather than fusing the two images into a combined conscious percept, what transpires is a pattern of perceptual alternations where one image dominates awareness while the other is suppressed; dominance alternates between the two images, typically every few seconds. This perceptual phenomenon is known as binocular rivalry. Binocular rivalry is considered useful for studying perceptual selection and awareness in both human and animal models, because unchanging visual input to each eye leads to alternations in visual awareness and perception. To create a binocular rivalry stimulus, all that is necessary is to present each eye with a different image at the same perceived location. There are several ways of doing this, but newcomers to the field are often unsure which method would best suit their specific needs. The purpose of this article is to describe a number of inexpensive and straightforward ways to create and use binocular rivalry. We detail methods that do not require expensive specialized equipment and describe each method's advantages and disadvantages. The methods described include the use of red-blue goggles, mirror stereoscopes and prism goggles.

Watch this Scientific Journal Video about How to Create and Use Binocular Rivalry at JoVE.com

How to Create and Use Binocular Rivalry

Binocular rivalry occurs when the eyes are presented with different images at the same location: one image dominates while the other is suppressed, and dominance alternates periodically. Rivalry is useful for investigating perceptual selection and visual awareness. Here we describe several easy methods for creating and using binocular rivalry stimuli.

Each of our eyes normally sees a slightly different image of the world around us. The brain can combine these two images into a single coherent ...

Nanyang Technological University

Research

JoVE Journal

Neuroscience

75.3K Views.  New York University. Binoculaire rivaliteit ontstaat wanneer de ogen worden gepresenteerd met verschillende afbeeldingen op dezelfde plaats: het ene beeld domineert, terwijl de andere wordt onderdrukt, en dominantie wisselt regelmatig. Rivaliteit is handig voor het onderzoeken van perceptuele selectie en visueel bewustzijn. Hier beschrijven we een aantal eenvoudige methoden voor het creëren en gebruiken van binoculaire rivaliteit stimuli.

Video: How to Create and Use Binocular Rivalry

VisualEyes: A Modular Software System for Oculomotor Experimentation

Eye movement studies have provided a strong foundation forming an understanding of how the brain acquires visual information in both the normal and dysfunctional brain.1 However, development of a platform to stimulate and store eye movements can require substantial programming, time and costs. Many systems do not offer the flexibility to program numerous stimuli for a variety of experimental needs. However, the VisualEyes System has a flexible architecture, allowing the operator to choose any background and foreground stimulus, program one or two screens for tandem or opposing eye movements and stimulate the left and right eye independently. This system can significantly reduce the programming development time needed to conduct an oculomotor study. The VisualEyes System will be discussed in three parts: 1) the oculomotor recording device to acquire eye movement responses, 2) the VisualEyes software written in LabView, to generate an array of stimuli and store responses as text files and 3) offline data analysis. Eye movements can be recorded by several types of instrumentation such as: a limbus tracking system, a sclera search coil, or a video image system. Typical eye movement stimuli such as saccadic steps, vergent ramps and vergent steps with the corresponding responses will be shown. In this video report, we demonstrate the flexibility of a system to create numerous visual stimuli and record eye movements that can be utilized by basic scientists and clinicians to study healthy as well as clinical populations.

Neural control and cognitive processes can be studied through eye movements. The VisualEyes software allows an operator to program stimuli on two computer screens independently using a simple, custom scripting language. The system can stimulate tandem eye movements (saccades and smooth pursuit) or opposing eye movements (vergence) or any combination.

Eye movement studies have provided a strong foundation forming an understanding of how the brain acquires visual information in both the normal and ...

The Measurement and Treatment of Suppression in Amblyopia

Amblyopia, a developmental disorder of the visual cortex, is one of the leading causes of visual dysfunction in the working age population. Current estimates put the prevalence of amblyopia at approximately 1-3%1-3, the majority of cases being monocular2. Amblyopia is most frequently caused by ocular misalignment (strabismus), blur induced by unequal refractive error (anisometropia), and in some cases by form deprivation.
Although amblyopia is initially caused by abnormal visual input in infancy, once established, the visual deficit often remains when normal visual input has been restored using surgery and/or refractive correction. This is because amblyopia is the result of abnormal visual cortex development rather than a problem with the amblyopic eye itself4,5 . Amblyopia is characterized by both monocular and binocular deficits6,7 which include impaired visual acuity and poor or absent stereopsis respectively. The visual dysfunction in amblyopia is often associated with a strong suppression of the inputs from the amblyopic eye under binocular viewing conditions8. Recent work has indicated that suppression may play a central role in both the monocular and binocular deficits associated with amblyopia9,10 .
Current clinical tests for suppression tend to verify the presence or absence of suppression rather than giving a quantitative measurement of the degree of suppression. Here we describe a technique for measuring amblyopic suppression with a compact, portable device11,12 . The device consists of a laptop computer connected to a pair of virtual reality goggles. The novelty of the technique lies in the way we present visual stimuli to measure suppression. Stimuli are shown to the amblyopic eye at high contrast while the contrast of the stimuli shown to the non-amblyopic eye are varied. Patients perform a simple signal/noise task that allows for a precise measurement of the strength of excitatory binocular interactions. The contrast offset at which neither eye has a performance advantage is a measure of the "balance point" and is a direct measure of suppression. This technique has been validated psychophysically both in control13,14 and patient6,9,11 populations.
In addition to measuring suppression this technique also forms the basis of a novel form of treatment to decrease suppression over time and improve binocular and often monocular function in adult patients with amblyopia12,15,16 . This new treatment approach can be deployed either on the goggle system described above or on a specially modified iPod touch device15.

Amblyopia is a developmental disorder of the visual cortex that is often accompanied by strong suppression of one eye. We present a new technique for measuring and treating interocular suppression in patients with amblyopia that can be deployed using virtual reality goggles or a portable iPod Touch device.

Amblyopia, a developmental disorder of the visual cortex, is one of the leading causes of visual dysfunction in the working age population. Current ...

Medicine

How to Build a Dichoptic Presentation System That Includes an Eye Tracker

The presentation of different stimuli to the two eyes, dichoptic presentation, is essential for studies involving 3D vision and interocular suppression. There is a growing literature on the unique experimental value of pupillary and oculomotor measures, especially for research on interocular suppression. Although obtaining eye-tracking measures would thus benefit studies that use dichoptic presentation, the hardware essential for dichoptic presentation (e.g. mirrors) often interferes with high-quality eye tracking, especially when using a video-based eye tracker. We recently described an experimental setup that combines a standard dichoptic presentation system with an infrared eye tracker by using infrared-transparent mirrors1. The setup is compatible with standard monitors and eye trackers, easy to implement, and affordable (on the order of US$1,000). Relative to existing methods it has the benefits of not requiring special equipment and posing few limits on the nature and quality of the visual stimulus. Here we provide a visual guide to the construction and use of our setup.

We recently proposed a method that allows dichoptic visual stimulus presentation and binocular eye tracking simultaneously1. The key is the combination of an infrared eye tracker and the corresponding infrared-transparent mirrors. This manuscript provides an in depth protocol for initial setup and everyday operation.

The presentation of different stimuli to the two eyes, dichoptic presentation, is essential for studies involving 3D vision and interocular suppression. ...

Behavior

Eye Tracking During Visually Situated Language Comprehension: Flexibility and Limitations in Uncovering Visual Context Effects

The present work is a description and an assessment of a methodology designed to quantify different aspects of the interaction between language processing and the perception of the visual world. The recording of eye-gaze patterns has provided good evidence for the contribution of both the visual context and linguistic/world knowledge to language comprehension. Initial research assessed object-context effects to test&#160;theories of modularity in language processing. In the introduction, we describe how subsequent investigations have taken the role of the wider visual context in language processing as a research topic in its own right, asking questions such as how our visual perception of events and of speakers contributes to&#160;comprehension informed by&#160;comprehenders&#39; experience. Among the examined aspects of the visual context are actions, events, a speaker&#39;s gaze, and emotional facial expressions, as well as spatial object configurations. Following an overview of the eye-tracking method and its different applications, we list the key steps of the methodology in the protocol, illustrating how to successfully use it to study visually-situated language comprehension. A final section presents three sets of representative results and illustrates the benefits and limitations of eye tracking for investigating the interplay between the perception of the visual world and language comprehension.

The present article reviews an eye-tracking methodology for studies on language comprehension. To obtain reliable data, key steps of the protocol must be followed. Among these are the correct set-up of the eye tracker (e.g., ensuring good quality of the eye and head images) and accurate calibration.

The present work is a description and an assessment of a methodology designed to quantify different aspects of the interaction between language processing ...

Stereoacuity Improvement using Random-Dot Video Games

Conventional amblyopia therapy involves occlusion or penalization of the dominant eye, though these methods enhance stereoscopic visual acuity in fewer than 30% of cases. To improve these results, we propose a treatment in the form of a video game, using random-dot stimuli and perceptual learning techniques to stimulate stereoacuity. The protocol is defined for stereo-deficient patients between 7-14 years of age who have already received treatment for amblyopia and have a monocular best corrected distance visual acuity of at least 0.1 logMAR. Patients are required to complete a perceptual learning program at home using the video game. While compliance is stored automatically in the cloud, periodic optometry center visits are used to track patient evolution and adjust the game&#39;s stereoscopic demand until the smallest detectable disparity is achieved. The protocol has proved to be successful, and effectiveness is gauged in terms of a two-level gain on a random stereoacuity test (global stereoacuity or cyclopean stereoacuity reference test). Moreover, the random-dot stimuli learning transfers to medial lateral stereoscopic acuity according to a Wirt Circles test, in which success criteria is a final stereoacuity of over 140&#34;, and the attained enhancement corresponds to no less than two levels of stereoscopic acuity. Six months later, a random-dot stereoacuity test recorded no reduction in the stereoacuity that was achieved.

Presented here is a protocol to improve stereoacuity using gamified perceptual learning software based on random-dot stimuli. Patients are stereo-deficient subjects without strabismus. The protocol combines optometry center visits with home exercises using software. Compliance and stereoacuity evolution are stored in the cloud.

Conventional amblyopia therapy involves occlusion or penalization of the dominant eye, though these methods enhance stereoscopic visual acuity in fewer ...

Assessing Binocular Central Visual Field and Binocular Eye Movements in a Dichoptic Viewing Condition

Macular degeneration typically results in heterogeneous binocular central visual defects. Currently available approaches to assess central visual field, like the microperimetry, can test only one eye at a time. Therefore, they cannot explain how the defects in each eye affect the binocular interaction and real-world function. Dichoptic stimulus presentation with a gaze-controlled system could provide a reliable measure of monocular/binocular visual fields. However, dichoptic stimulus presentation and simultaneous eye-tracking are challenging because optical devices of instruments that present stimulus dichoptically (e.g., haploscope) always interfere with eye-trackers (e.g., infrared video-based eye-trackers). Therefore, the goals were 1) to develop a method for dichoptic stimulus presentation with simultaneous eye-tracking, using 3D-shutter glasses and 3D-ready monitors, that is not affected by interference and 2) to use this method to develop a protocol for assessing central visual field in subjects with central vision loss. The results showed that this setup provides a practical solution for reliably measuring eye-movements in dichoptic viewing condition. In addition, it was also demonstrated that this method can assess gaze-controlled binocular central visual field in subjects with central vision loss.

Presented here is a protocol for assessing binocular eye movements and gaze-controlled central visual field screening in participants with central vision loss.

Macular degeneration typically results in heterogeneous binocular central visual defects. Currently available approaches to assess central visual field, ...

Monocular Visual Deprivation and Ocular Dominance Plasticity Measurement in the Mouse Primary Visual Cortex

Monocular visual deprivation is an excellent experimental paradigm to induce primary visual cortical response plasticity. In general, the response of the cortex to the contralateral eye to a stimulus is much stronger than the response of the ipsilateral eye in the binocular segment of the mouse primary visual cortex (V1). During the mammalian critical period, suturing the contralateral eye will result in a rapid loss of responsiveness of V1 cells to contralateral eye stimulation. With the continuing development of transgenic technologies, more and more studies are using transgenic mice as experimental models to examine the effects of specific genes on ocular dominance (OD) plasticity. In this study, we introduce detailed protocols for monocular visual deprivation and calculate the change in OD plasticity in mouse V1. After monocular deprivation (MD) for 4 days during the critical period, the orientation tuning curves of each neuron are measured, and the tuning curves of layer four neurons in V1 are compared between stimulation of the ipsilateral and contralateral eyes. The contralateral bias index (CBI) can be calculated using each cell&#39;s ocular OD score to indicate the degree of OD plasticity. This experimental technique is important for studying the neural mechanisms of OD plasticity during the critical period and for surveying the roles of specific genes in neural development. The major limitation is that the acute study cannot investigate the change in neural plasticity of the same mouse at a different time.

Here, we present detailed protocols for monocular visual deprivation and ocular dominance plasticity analysis, which are important methods for studying the neural mechanisms of visual plasticity during the critical period and the effects of specific genes on visual development.

Monocular visual deprivation is an excellent experimental paradigm to induce primary visual cortical response plasticity. In general, the response of the ...

Developmental Biology

Evaluating Optokinetic Reflex Responses in Mice: A New High-Precision Protocol

Quantification of Visual Feature Selectivity of the Optokinetic Reflex in Mice

The optokinetic reflex (OKR) is an essential innate eye movement that is triggered by the global motion of the visual environment and serves to stabilize retinal images. Due to its importance and robustness, the OKR has been used to study visual-motor learning and to evaluate the visual functions of mice with different genetic backgrounds, ages, and drug treatments. Here, we introduce a procedure for evaluating OKR responses of head-fixed mice with high accuracy. Head fixation can rule out the contribution of vestibular stimulation on eye movements, making it possible to measure eye movements triggered only by visual motion. The OKR is elicited by a virtual drum system, in which a vertical grating presented on three computer monitors drifts horizontally in an oscillatory manner or unidirectionally at a constant velocity. With this virtual reality system, we can systematically change visual parameters like spatial frequency, temporal/oscillation frequency, contrast, luminance, and the direction of gratings, and quantify tuning curves of visual feature selectivity. High-speed infrared video-oculography ensures accurate measurement of the trajectory of eye movements. The eyes of individual mice are calibrated to provide opportunities to compare the OKRs between animals of different ages, genders, and genetic backgrounds. The quantitative power of this technique allows it to detect changes in the OKR when this behavior plastically adapts due to aging, sensory experience, or motor learning; thus, it makes this technique a valuable addition to the repertoire of tools used to investigate the plasticity of ocular behaviors.

Author Spotlight: An Accurate and Quantitative Approach to Study Visual Feature Selectivity of the Optokinetic Reflex in Mice 

Here, we describe a standard protocol for quantifying the optokinetic reflex. It combines virtual drum stimulation and video-oculography, and thus allows precise evaluation of the feature selectivity of the behavior and its adaptive plasticity.

The optokinetic reflex (OKR) is an essential innate eye movement that is triggered by the global motion of the visual environment and serves to stabilize ...

 Evaluating Stereopsis in Unilateral Amblyopia: A Comparative Study

Comparison of Three Clinical Stereoscopic Methods for Measuring Binocular Visual Function During Amblyopic Treatment in Unilateral Amblyopia

This study aimed to compare the measuring stereopsis results of unilateral amblyopia during amblyopic treatment by employing some of the most widely used clinical tests. Thirty-four individuals with previously untreated unilateral amblyopia, aged 8.4 &#177; 2.7 years, were included in the study. Monocular (best corrected visual acuity [BCVA] at distance) and binocular (including Titmus, Random-dot, and Frisby stereopsis) visual functions were measured at baseline and 2-month and 6-month visits after synthetical treatment.
We found that Titmus stereopsis was always significantly better than Random-dot stereopsis (p &#60; 0.001). Frisby stereopsis was also always significantly better than Random-dot stereopsis (p &#60; 0.001). However, there was no significant difference between Titmus stereopsis and Frisby stereopsis (p = 0.562). However, interestingly, there was no significant difference in the mean improvement of the three stereopsis methods from baseline to the 2-month visit, F = 1.158, p = 0.318.
Similarly, a significant difference was also lacking in the mean improvement of the three stereopsis methods from baseline to the 6-month visit, F = 0.302, p = 0.740. We conclude that there will be different results obtained from different stereopsis measuring methods used to measure amblyopia in patients. We recommend performing at least two types of stereoscopic measurements to evaluate each case of amblyopia. However, for observing therapeutic effects, each measurement method has the same performance for clinical results during amblyopic treatment.

Here, we present three common stereopsis measurement methods to measure patients with amblyopia and the comparison of the efficacy of different methods.

This study aimed to compare the measuring stereopsis results of unilateral amblyopia during amblyopic treatment by employing some of the most widely used ...

Color Afterimages

Source: Laboratory of Jonathan Flombaum&#8212;Johns Hopkins University
Human color vision is impressive. People with normal color vision can tell apart millions of individual hues. Most amazingly, this ability is achieved with fairly simple hardware.
Part of the power of human color vision comes from a clever bit of engineering in the human brain. There, color perception relies on what is known as an &#39;opponent system.&#39; This means that the presence of one kind of stimulus is treated as evidence for the absence of another, and vice versa; absence of one kind of stimulus is taken as evidence for the presence of the other. In particular, in the human brain there are cells that fire both when they receive signals to suggest that blue light is present, or when they do not receive signals suggesting yellow light. Similarly, there are cells that fire in the presence of yellow or the absence of blue. Blue and yellow are thus treated as opponent values in one dimension, and can be thought of as negative versus positive values on one axis of a Cartesian plane. If a stimulus is characterized as having a negative value on that axis, it can&#39;t also have a positive value. So, if it is characterized as yellow, it can&#39;t also be characterized as blue. Similarly, green and red (or really, magenta), occupy another opponent dimension. There are cells in the human brain that respond to the presence of one or the absence of the other. Figures 1 and 2 explain color opponency in Cartesian terms.
<img alt="Figure 1" src="/files/ftp_upload/10194/10194fig1.jpg" /> 
Figure 1. Opponent color dimensions. The human brain processes color using an opponent dimensions system. This is a two-dimensional plane with blue and yellow occupying one axis, which can be thought of as simply positive or negative, and red and green occupying the other axis. The consequence of the system is that the brain processes the presence of some colors as indicating the absence of others, and vice-versa. All perceivable colors occupy a point in the opponent space.
<img alt="Figure 2" src="/files/ftp_upload/10194/10194fig2.jpg" /> 
Figure 2. All perceivable colors occupy a point in the opponent space. Shown here are examples of colors that have nonzero values in each of two dimensions of the opponent space.
One way that color opponency was discovered-in 1878 by Ewald Hering, even before scientists had access to techniques for imaging the brain itself-is through an illusion known as a color afterimage. Afterimages are still used today both to demonstrate the opponent properties of human color perception and to study them.
This video demonstrates how to create a color afterimage illusion, and a simple way to collect subjective perceptual responses from human observers.

Studying Color Perception Using Color Afterimages Visual Illusion

Source: Laboratory of Jonathan Flombaum&#8212;Johns Hopkins University
Human color vision is impressive. People with normal color vision can tell apart ...

How to Create and Use Binocular Rivalry

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