The effect of practice on binocular rivalry control

The effects of passive viewing and the practice of the control instructions, “slow rate” and “rapid rate,” on a measure of binocular rivalry (BR) control was investigated. Four groups of 8 Ss each had different amounts of passive viewing of BR followed by different amounts of control instructions to complete a total of 50 min of testing spaced over lOdays. There were increases of passive rate as long as Ss practiced only the “passive rate“ instructions. This had an effect of increasing the rapid rate and slow rate of the first control practice day. However, “passive rate” practice had no significant effect on the measure of BR control. Successive practice days of “rapid rate” and “slowrate” instructions produced an increase in rapid rate and decrease in slow rate resulting in an increase in the measure of control.     

Objective measurement of dominance control in binocular rivalry

Six male as attempted to identify stimuli superimposed on either of two dichoptically viewed rivalry patterns. Ability to influence dominance switches was confirmed with this objective procedure, by reason of a decreased error rate (1) with 3-sec advance knowledge as to which pattern would receive a test stimulus, and (2) with knowledge that an 83% majority of all stimuli would be presented in a given field. However, even when test stimuli were self-initiated, dominant-field and suppressed-field scores were not close to the error rates predicted on the basis of monocular levels and of random guessing, respectively, indicating either misjudgments of pattern dominance or, more likely, a failure of the dominant field to totally suppress its opponent.     

Amplitude of visual suppression during the control of binocular rivalry

To investigate the precise mechanism of control of binocular rivalry, Ss were instructed to attend actively to whichever pattern was momentarily in the nonsuppression phase. Test stimuli were presented tachistoscopically for recognition in either phase of rivalry. Because the differential recognition between nonsuppressed and suppressed phases was no greater for an active condition than for a passive viewing condition, it was concluded that control is not mediated by varying the amplitude of the suppression effect. This result was consistent with control that is exercised by selecting the eye to receive a constant amplitude suppression. In addition, it was found that visual sensitivity of rivalry nonsuppression and nonrivalry were the same for the ocular dominant eye but different for the nondominant eye.     

The role of accommodation in the control of binocular rivalry

The role of accommodation in the control of binocular rivalry (BR) has been granted various degrees of importance by Es in the past. The most recent investigation by Fry (1936) concluded that accommodation provides the basis of BR control through the blurring of retinal images. However, the present study found that the introduction of very small artificial pupils (0.5 mm) did not reduce BR control. It was concluded that if accommodation changes are occurring with large pupils, the resulting image blurring plays no part in control of rivalry. Experiment 2 tested the effect of paralyzed intrinsic eye muscles and found almost the same degree of control as in the normal state. The slight decrease of control that was present was attributed to a general performance decrement, since slight performance decrements with eye paralysis were also found in a visual reaction-time task and hand dynamometer test. In Experiment 3, it was found that the increased control that was obtained over several practice sessions was mostly retained during subsequent eye paralysis. These findings and, in addition, a very significant control of rivaling afterimage stimuli under eye paralysis strongly suggest a central component of BR control rather than one based on accommodation.     

Aftereffects in binocular rivalry

Five experiments are reported in which the aftereffect paradigm was applied to binocular rivalry. In the first three experiments rivalry was between a vertical grating presented to the left eye and a horizontal grating presented to the right eye. In the fourth experiment the rivalry stimuli consisted of a rotating sectored disc presented to the left eye and a static concentric circular pattern presented to the right. In experiment 5 rivalry was between static radiating and circular patterns. The predominance durations were systematically influenced by direct (same eye) and indirect (interocular) adaptation in a manner similar to that seen for spatial aftereffects. Binocular adaptation produced an aftereffect that was significantly smaller than the direct aftereffect, but not significantly different from the indirect one. A model is developed to account for the results; it involves two levels of binocular interaction in addition to monocular channels. It is suggested that the site of spatial aftereffects is the same as that for binocular rivalry, rather than sequentially prior.     

Attention speeds binocular rivalry

During binocular rivalry, incompatible images presented dichoptically compete for perceptual dominance. It has long been debated whether binocular rivalry can be controlled by attention. Most studies have shown that voluntary control over binocular rivalry is limited. We sought to remove attention from binocular rivalry by presenting a concurrent task. Diverting attention slowed the rivalry alternation rate, and did so in proportion to the difficulty of the concurrent task. Even a very demanding distractor task, however, did not arrest rivalry alternations completely. Given that diverting attention was equivalent to lowering the contrast of the rival stimuli, the ability of attention to speed binocular rivalry is most likely due to an increase in the effective contrast of the stimuli through boosting the gain of the cortical response. This increase in effective contrast will ultimately lead to a perceptual switch, thereby limiting voluntary control. Thus, attention speeds rivalry alternations, but has no inherent control over the rivalry process.     

Shifting spatial attention makes you flip: Exogenous visual attention triggers perceptual alternations during binocular rivalry

Although it has been argued that visual attention and the dynamics of binocular rivalry are closely linked, strong evidence for this proposition is still lacking. Here, we investigate how perceptual alternations during binocular rivalry are affected by spatial attention by employing a cuing paradigm. We show a tight link between the occurrence of perceptual alternations and the spatiotemporal properties of visual attention: Alternations occurred earlier and more frequently at locations where visual attention was summoned by an exogenous cue. We argue that cuing a location where rival images are presented leads to a transient increase in the effective contrast of these rival images. This transient increase in effective contrast increases the probability of an alternation at that location. Furthermore, we suggest that an occipito-fronto-parietal network known to be involved in selective attention and binocular rivalry mediates perceptual alternations by boosting the neural response at attended locations.     

The role of voluntary and involuntary attention in selecting perceptual dominance during binocular rivalry

When incompatible images are presented to corresponding regions of each eye, perception alternates between the two monocular views (binocular rivalry). In this study, we have investigated how involuntary (exogenous) and voluntary (endogenous) attention can influence the perceptual dominance of one rival image or the other during contour rivalry. Subjects viewed two orthogonal grating stimuli that were presented to both eyes. Involuntary attention was directed to one of the grating stimuli with a brief change in orientation. After a short period, the cued grating was removed from the image in one eye and the uncued grating was removed from the image in the other eye, generating binocular rivalry. Subjects usually reported dominance of the cued grating during the rivalry period. We found that the influence of the cue declined with the interval between its onset and the onset of binocular rivalry in a manner consistent with the effect of involuntary attention. Finally, we demonstrated that voluntary attention to a grating stimulus could also influence the ongoing changes in perceptual dominance that accompany longer periods of binocular rivalry Voluntary attention did not increase the mean dominance period of the attended grating, but rather decreased the mean dominance period of the non-attended grating. This pattern is analogous to increasing the perceived contrast of the attended grating. These results suggest that the competition during binocular rivalry might be an example of a more general attentional mechanism within the visual system.     

Neural bases of binocular rivalry

During binocular rivalry, conflicting monocular images compete for access to consciousness in a stochastic, dynamical fashion. Recent human neuroimaging and psychophysical studies suggest that rivalry entails competitive interactions at multiple neural sites, including sites that retain eye-selective information. Rivalry greatly suppresses activity in the ventral pathway and attenuates visual adaptation to form and motion; nonetheless, some information about the suppressed stimulus reaches higher brain areas. Although rivalry depends on low-level inhibitory interactions, high-level excitatory influences promoting perceptual grouping and selective attention can extend the local dominance of a stimulus over space and time. Inhibitory and excitatory circuits considered within a hybrid model might account for the paradoxical properties of binocular rivalry and provide insights into the neural bases of visual awareness itself.     

Temporal perturbations of binocular rivalry

Successive durations of binocular rivalry are sequentially independent, random variables. To explore the underlying control process, we perturbed the cycle during a 30-sec viewing period by immediately forcing an eye to return to dominance whenever it became suppressed. During this period of forced dominance, that eye's individual dominance durations were unusually brief, but immediately following the period of forced dominance that eye's suppression durations were unusually long. However, no long-term change in the sequential pattern of rivalry occurred, and the stochastic independence of successive durations was maintained during and following the period of forced dominance. The same pattern of results was obtained with even longer periods of forced dominance. These results are consistent with the existence of a short-term adaptation, or fatigue, process responsible for transitions from dominance to suppression.     

Contour synchrony in binocular rivalry

Afterimages of rivalrous vertical and horizontal lines were generated simultaneously in each eye. Either a horizontal and a vertical line or two vertical lines were presented to one eye with the complementary rivalrous pair to the other eye. Synchrony of line pairs presented to the same eye was longer than predicted on the basis of independence, irrespective of the monocular configuration. Furthermore, there appeared to be a facilitatory effect for lines of the same orientation if they were presented to one eye rather than combined from both eyes.     

Oculomotor effects upon binocular rivalry

Summary Binocular rivalry was generated by projecting dissimilar Julesz-type patterns to each eye. The minimum angular width of the patterns needed to observe rivalry was measured at four retinal eccentricities for two simulated viewing distances: 200 and 20 cm. The angular width needed to just detect rivalry was up to 50% greater for the 20 cm viewing distance as compared with the threshold width measured at 200 cm. This increased tolerance for rivalry for near fixation was inversely proportional to the change in apparent size. The results suggest that the lateral geniculate nucleus is the site of size-scaling or zooming.Supported by the U. S. Air Force under contract No. AFOSR-F44620-67-C0085, with supplementary funding to Prof. H.-L. Teuber, Chairman, from NASA and NIMH under grants NsG 496 and MH 05673.     

Microsaccadic eye movements and binocular rivalry

Eye movements were monitored with a sensitive binocular measuring device during presentation of stimuli that caused binocular rivalry. It was found that the number of microsaccades was approximately 50% higher when measured during rivalry than when measured during periods of normal viewing. The level of microsaccadic activity is greater at the beginning than toward the end of the suppression interval. The results suggest that the depth of suppression associated with binocular rivalry is not constant over the duration of a rivalry interval.     

Aging and the depth of binocular rivalry suppression

Two experiments were designed to examine the effect of aging on the strength of binocular rivalry suppression. To produce rivalry, orthogonally oriented sine-wave luminance gratings were presented dichoptically. The observers were then required either to discriminate the spatial location of a probe spot presented to the dominant or suppressed eye's view or to detect the presence or absence of the probe. The observers in the younger and older age groups exhibited typical rivalry suppression for both tasks (i.e., the probe was more difficult to detect or discriminate when presented to the suppressed eye), but the magnitude of the suppression was significantly larger in the older observers. This increased suppression that accompanies aging can be explained by a reduction in the inhibition produced by the binocular matching circuitry of S. R. Lehky and R. Blake's (1991) model.     

Stochastic properties of binocular rivalry alternations

The extent to which binocular rivalry phases are sequentially related was assessed by theν statistic and by autocorrelation. Both measures indicate that the duration of successive phases are independent. The frequency distributions of suppression phases and of nonsuppression phases can be fitted by gamma distributions. These results are consistent with models of the rivalry process that incorporate independence assumptions.     

Stochastic properties of binocular rivalry alternations

Previous researches have demonstrated that the successive phase durations in binocular rivalry are independent. These findings are confirmed and extended to chromatic stimuli. The nature of the function that is shown to describe the distribution of the dominance phase durations is consistent with the independence of successive phases and suggests that a parallel may exist between binocular rivalry and the perceptual reversal of ambiguous figures.

     

A neural theory of binocular rivalry

When the two eyes view discrepant monocular stimuli, stable single vision gives way to alternating periods of monocular dominance; this is the well-known but little understood phenomenon of binocular rivalry. This article develops a neural theory of binocular rivalry that treats the phenomenon as the default outcome when binocular correspondence cannot be established. The theory posits the existence of monocular and binocular neurons arrayed within a functional processing module, with monocular neurons playing a crucial role in signaling the stimulus conditions instigating rivalry and generating inhibitory signals to implement suppression. Suppression is conceived as a local process happening in parallel over the entire cortical representation of the binocular visual field. The strength of inhibition causing suppression is related to the size of the pool of monocular neurons innervated by the suppressed eye, and the duration of a suppression phase is attributed to the strength of excitation generated by the suppressed stimulus. The theory is compared with three other contemporary theories of binocular rivalry. The article closes with a discussion of some of the unresolved problems related to the theory.