Binocular Rivalry Suppression Research Articles

Spectral characteristics of blink suppression in normal observers

Previous studies of the characteristics of suppression occurring under various visual conditions show similarities and differences which may be indicative of the mechanism of suppression. The primary purpose of this study was to determine if the suppression that occurs in response to an eyelid blink (blink suppression) is similar to that which occurs during a saccade (saccadic suppression). In addition, the characteristics of blink suppression and other forms of suppression (i.e. permanent and binocular rivalry suppression) are compared. A test probe paradigm was utilized to determine the effect of blink suppression on the spectral sensitivity function in three normal observers. Employing a two alternative forced choice technique, thresholds were determined for wavelengths from 420 to 680 nm in 20 nm steps. At each wavelength, the threshold was determined at 0 and 400 msec after the onset of a voluntary blink. The magnitude of suppression was taken as the difference between the 0 and 400 msec thresholds. Similar to saccadic suppression, the magnitude of blink suppression increased as the stimuli biased detection towards the luminance channel. These results suggest that blink suppression and saccadic suppression are the result of a single mechanism. Similarities between blink suppression and other forms of visual suppression are also considered.

Interocular Suppression Produced by Rivalry Stimuli: A Comparison of Normal and Abnormal Binocular Vision

This study compares interocular suppression in subjects with early strabismus and/or anisometropia with binocular rivalry suppression in subjects with normal binocular vision. A psychophysical test-probe paradigm was used to measure the changes in luminance-increment detection thresholds associated with periods of phenomenal suppression. In subjects with normal binocular vision, rivalry suppression induced by viewing orthogonally oriented grating pairs produced a distinctive wavelength-dependent change in visual sensitivity; specifically, there was a greater reduction in sensitivity for short (e.g., 450 nm) vs. middle or long wavelength stimuli (e.g., 560 nm). In contrast, subjects with abnormal binocular vision, regardless of the type of early abnormal visual experience, showed more reduction in sensitivity for a 560-nm stimulus than for the short-wavelength, 450-nm stimulus. Moreover, the pattern of sensitivity change in subjects with abnormal binocular vision was the same for suppression induced by either rivalry stimuli or stimuli that would normally promote fusion. The results clearly indicate that interocular suppression in subjects with abnormal binocular vision is qualitatively different from normal binocular rivalry. Evidently, the processes that mediate binocular rivalry are very susceptible to environmental influences during early vision development and can be disrupted easily.

Visual disturbance of the uncovered eye in patients wearing an eye patch.

We questioned 104 consecutive eye casualty patients about any visual disturbance experienced while wearing an eye patch as part of their treatment. Many (31%) reported momentary loss of vision in the uncovered eye. Some experienced this while driving. It was more common (p < 0.0008) if the 'dominant eye' had been patched (47%) rather than the 'non-dominant eye' (16%). In a separate experiment, a number of co-operative subjects were provided with a translucent-coloured occluder to be worn over each eye in turn. They reported a recurring coloured interference in the uncovered eye sparing the monocular crescent. We propose that the loss of vision in the unpatched eye is due to binocular rivalry suppression by the patched eye. This visual disturbance may be a cause of anxiety or risk for the patient. Patched patients should be warned this may occur, and advised to avoid driving or operating machinery.

Interocular suppression in normal and amblyopic subjects: the effect of unilateral attenuation with neutral density filters.

In normal subjects, binocular rivalry suppression takes time to build up (Wolfe, 1986a). The time courses of interocular suppression are different and heterogeneous in amblyopic subjects (de Belsunce & Sireteanu, 1991). In the present study, we found that, in normal observers, progressive reduction of one eye's stimulus luminance with neutral density filters produces time courses similar to those of amblyopic subjects. Conversely, in amblyopes, attenuation of the dominant eye's stimulus produces time courses similar to those of normal observers. Under conditions of balancing of the two eyes, amblyopes experience alternating suppression, similarly to binocular rivalry of normals.

Binocular rivalry suppression disrupts recovery from motion adaptation.

The motion aftereffect (MAE) lasts longer when the test period does not immediately follow adaptation, a phenomenon called storage. Does storage of the MAE occur if the test target is present but rendered phenomenally invisible owing to the presence of a rival target presented to the other eye during the storage period? Our experiment addressed this question. Following adaptation to a drifting grating, an intervening period preceded testing with a stationary grating. During this period, the adapted eye either viewed the test target immediately or was occluded, and the unadapted eye either viewed a high-contrast rival target or was occluded. Thus four conditions were employed. The duration of the residual MAE was found to be longer for the rivalry condition (grating and rival target viewed) than for the normal MAE condition (grating viewed), and comparable to that in the stored MAE condition (both eyes occluded). Thus, the MAE is stored when the test target is rendered invisible due to binocular rivalry, indicating that a suppressed target is ineffective at promoting decay of the MAE. So while suppression does not prevent information about the adapting grating from reaching the site of generation of the MAE (Lehmkuhle & Fox, 1975), it can prevent information about the test target from reaching the site of the stored MAE. Current models attribute the MAE to reduced responsiveness of direction-selective cortical neurons (Sutherland, 1961; Barlow & Hill, 1963). Thus, storage should reflect a differential return of these adapted cells to preadapted response levels, dependent on postadaptation stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of interocular suppression on spectral sensitivity.

A stable form of interocular suppression, referred to as "permanent suppression," can be produced by presenting a contoured field to one eye and a spatially homogenous field to the fellow eye, a viewing condition analogous to the classic "hole-in-the-hand" illusion. We examined the relation between permanent suppression and binocular rivalry suppression by comparing the changes in the increment-threshold spectral sensitivity function produced by these two forms of suppression. Permanent suppression produced a reduction in spectral sensitivity; however, in contrast to binocular rivalry suppression, the sensitivity alterations associated with permanent suppression were independent of the test-probe wavelength. The different patterns of sensitivity loss observed during binocular rivalry and permanent suppression indicate that different neural mechanisms mediate these two forms of interocular suppression.

Orientation and spatial-frequency-specific surround effects on binocular rivalry

The presence of an annular grating surrounding rivaling gratings was found to significantly reduce the dominance of a component that was similar in both spatial frequency and orientation. This effect, which transfers interocularly, would seem to implicate cortical or higher mechanisms in binocular rivalry suppression.

Apparent motion can survive binocular rivalry suppression

For short-range motion, observers dichoptically viewed a random-dot cinematogram and a rival target. Upon keypress, the first frame of the cinematogram was replaced by the second frame. Observers judged the direction of motion, which was governed by the initial position of the central region. Performance was well above chance during both dominance and suppression. For long-range motion, observers rated the motion produced by sequentially flashing two small spots, with the first spot contained within a rivalrous region. Suppression reduced but did not prevent perception of this motion. Presenting the second motion frame to both eyes weakened both forms of motion.

Clinical suppression and binocular rivalry suppression: The effects of stimulus strength on the depth of suppression

In observers with abnormal binocular vision (such as strabismics or anisometropes) one eye's view is often suppressed. This clinical suppression serves to eliminate binocular diplopia and confusion. Suppression may also occur in observers with normal binocular vision, when the two eyes view disparate retinal images, a phenomenon known as binocular rivalry. When the image in an eye is suppressed, it is possible to determine the amount by which that suppressed stimulus is below the visibility threshold, or the depth of suppression. In the experiments presented here, the depth of suppression in an eye was measured as the strength of the stimulus in the contralateral eye (the stimulus inducing suppression) was varied. This was done for both clinical suppressors and normal observers undergoing binocular rivalry suppression. Independent changes were made to the contrast, the luminance, and the spatial frequency of the inducing stimulus. For both clinical suppression and binocular rivalry suppression, the depth of suppression was constant, regardless of the changes to the inducing stimulus.

Strength of Suppression in Binocular Rivalry Immediately after Onset and Offset of Suppressing Pattern

If the dichoptic viewing method is used to analyze functions of the human brain rather than binocular rivalry itself, temporal properties of suppression come up as an important problem. To clarify the properties, a method in which test and suppressing patterns can be presented on any temporal condition was devised. When the suppressing pattern was flickered, the strength of suppression immediately after the onset of the pattern approached a maximum at the intercycle interval of 3 sec. It also increased with the increasing duration of exposure and reached a maximum at about 100 msec. The strength of suppression immediately after the offset decreased rapidly but continuously as time went on. These results indicate that the on-effect is produced by the presentation of the suppressing pattern, not the off-effect by its removal, whereas physiological data generally show the strong effect both at “on” and “off” of a light stimulus.

Fitting index of predominance based on periodicity of strengths of pattern and suppression in binocular rivalry.

The predominance of the strength of pattern over the strength of suppression during binocular rivalry has generally been defined as the percentage of total time of appearance. Is this fit for an index of the predominance? Theoretically, the strengths of pattern and suppression periodically oscillate throughout the observation period. From this assumption, the best fitting indices of predominance were examined. The simplest model of the visual system was one in which the periodicity of the two originates was expressed by a differential equation. Various indices were examined by the solution of its equation so that a power function of the ratio of the time of appearance to that of disappearance was obtained as the most suitable index of the predominance.

Briefly presented stimuli can disrupt constant suppression and binocular rivalry suppression.

An earlier study has shown that the intermittent suppression of one monocular stimulus by another in binocular rivalry does not occur when normally rivalrous stimuli are briefly presented. Constant suppression of stimuli presented to one eye is a common consequence of esotropia during development. A study is reported which demonstrates that constant suppression does not occur when stimuli are briefly presented. The dependence of suppression on stimulus duration is similar in both forms of suppression.

Periodicity of strength of pattern in binocular rivalry.

The effect of suppression in binocular rivalry is divided into the effects of boundary and of region. By removing the effect of boundary from the double effects, we examined whether the strength of pattern oscillates throughout duration of suppression phase. Probabilities of appearance of the suppressed test patterns were measured immediately after the removal of the suppressing pattern at various temporal points after onset of suppression. The probabilities decrease, reach a minimum level, and then increase throughout the course of the suppression phase. Immediately after the beginning of the suppression phase, the small test pattern whose duration of suppression is short rarely appears, while the large pattern whose duration of suppression is long certainly appears. These results support our hypothesis for which the key assumption is that the strength of pattern periodically oscillates as a function of duration of observation time.

Method for measuring strength of suppression in binocular rivalry.

A method for measuring the strength of suppression of a suppressing pattern is examined. The test pattern was a black filled circle 1 degree in diameter and suppressing patterns were black outline circles 1, 1.2, 1.5, 2, 3, and 4 degrees in inner diameter, respectively. Each subject (2 men, 2 women) was asked to report the frequency of suppression phases of the test pattern immediately after presentation of the suppressing pattern. Analysis indicated that the method used is effective as a way of analyzing the rivalry process and the effect of eyedness.

Binocular rivalry suppression interferes with phase adaptation

With extended viewing, a triangle-wave grating takes on an unstable, illusory appearance, such that at times it more nearly resembles a square-wave grating. Prior adaptation to a genuine square-wave grating temporarily reduces the incidence of this illusory percept, stabilizing the appearance of a triangle-wave grating. The present experiment measured the effect of adapting to a square-wave grating that was suppressed during binocular rivalry for a substantial portion of the adaptation period. Rivalry suppression reduced the effectiveness of the adaptation pattern, indicating that the neural site of adaptation follows the locus of suppression.

Rivalry with continuous and flashed stimuli as a measure of ocular dominance across the visual field.

Two measures of sensory ocular dominance were compared. Both involved dichoptic presentation of orthogonal gratings--a situation which results in binocular rivalry. The gratings were presently briefly in experiment 1 and continuously in experiment 2 and by the predominance of one grating over the other a quantitative estimation of ocular dominance was obtained in both cases. Comparison of the results showed that (a) binocular rivalry suppression was present for exposures of 250 ms and (b) the briefly presented gratings were a more sensitive test for ocular dominance than conventional continuously presented stimuli. The variation of dominance over the horizontal meridian of the visual field was considered. For many subjects a consistent different in the ocular dominance in the two halves of the visual field, and therefore of the cortex, was found. Some showed dominance of the ipsilateral eye in each hemisphere while others showed dominance of the contralateral eye. It was found that there is, in fact, a continuum of types of dominance pattern amongst individuals.

網膜の垂直軸方向における視野闘争抑制の特性

A hypothesis has been advanced which suggests that the magnitude of suppression in binocular rivalry along the horizontal meridian is stronger at the center of the rivalrous pattern than at its peripheral. It was tested whether this hypothesis can be extended to the vertical meridian. Accuracy in detecting a briefly flashed target superimposed upon the completely suppressed pattern during binocular rivalry was measured at each of two target positions combined with two fixation positions along the vertical meridian (Exp. I). As a control experiment, target-detection performance in monocular observation was examined (Exp. II), The results obtained from one of the two subjects supported this hypothesis, although the effect of position within the rivalrous pattern was less marked than that obtained along the horizontal meridian. The results obtained from the other subject suggested that there was little difference in suppression effect between the center and the upper end of the pattern. These results suggest that the variation in suppression effect within the pattern along the vertical meridian is smaller than that along the horizontal meridian.

The sensitivity of binocular rivalry suppression to changes in orientation assessed by reaction-time and forced-choice techniques.

Binocular rivalry was induced between two orthogonal square-wave gratings of the same spatial frequency, luminance, contrast, and field size, presented dichoptically. One of the gratings could be instantly replaced by a third grating differing only in orientation. In one experiment subjects were required to respond as soon as an orientation change was noticed, and to withhold response to catch trials (no orientation change). When orientation changes were made to the visible grating, reaction time was found to be a U-shaped function of the magnitude of orientation change. When orientation changes were made to the grating undergoing binocular-rivalry suppression, an overall increase in reaction time was found with the increase being greater for large orientation changes (an asymmetrical U-shaped function). In another experiment subjects were required to detect the direction of a change in orientation in a two-alternative forced-choice procedure. Thresholds were thus obtained for 75% correct performance. It was found that thresholds for orientation changes made to the visible and invisible fields were identical from 20 degrees to 70 degrees orientation change. Outside this range thresholds were higher when orientation changes were made to the field suppressed by binocular rivalry. It is argued that the orientation functions obtained in the two experiments may represent incomplete suppression of either form or transient information during binocular rivalry.

The effect of contrast on the completeness of binocular rivalry suppression.

Binocular rivalry between orthogonal sine wave gratings was studied by asking subjects to indicate when they saw just one or the other grating, as opposed to a composite. Using this measure, it was found that the completeness of rivalry (1) usually increased with grating contrast; (2) increased as a trial progressed, up to about 40 sec; and (3) depended on spatial frequency, with the optimal spatial frequency being lower than that at which contrast sensitivity was maximal. These findings supplement what has been learned about rivalry by other methods.

The site of binocular rivalry suppression.

Two experiments were performed to localize the site of binocular rivalry suppression in relation to the locus of grating adaptation. In one experiment it was found that phenomenal suppression of a high-contrast adaptation grating presented to one eye had no influence on the strength of the threshold-elevation aftereffect measured interocularly. Evidently information about the adaptation grating arrives at the site of the aftereffect (presumably binocular neurons) even during suppression. In a second experiment 60 s of grating adaptation was found to produce a short-term reduction in the predominance of the adapted eye during binocular rivalry. These findings provide converging lines of evidence that suppression occurs at a site in the human visual system after the locus of grating adaptation and, hence, after the striate cortex.