Rivalry Suppression Research Articles

Normalization Regulates Competition for Visual Awareness

Signals in our brain are in a constant state of competition, including those that vie for motor control, sensory dominance, and awareness. To shed light on the mechanisms underlying neural competition, we exploit binocular rivalry, a phenomenon that allows us to probe the competitive process that ordinarily transpires outside of our awareness. By measuring psychometric functions under different states of rivalry, we discovered a pattern of gain changes that are consistent with a model of competition in which attention interacts with normalization processes, thereby driving the ebb and flow between states of awareness. Moreover, we reveal that attention plays a crucial role in modulating competition; without attention, rivalry suppression for high-contrast stimuli is negligible. We propose a framework whereby our visual awareness of competing sensory representations is governed by a common neural computation: normalization.

Binocular rivalry: competition and inhibition in visual perception.

When the brain is presented with ambiguous visual stimuli supporting two interpretations, perception becomes bistable and alternates over time between one interpretation and the other. This process contains elements of competition (between the rivaling percepts) as well as inhibition, as the percepts are mutually exclusive so that one is always suppressed. This review covers the most widely studied form of bistable perception-binocular rivalry. Suppression in rivalry is covered in detail, including discussion of its general and specific components, its local nature and spatial organization, techniques for quantifying it, and the role of global feedback. The competitive dynamics of rivalry are discussed within the context of the classical 'adapting reciprocal inhibition' model of rivalry and recent evidence supporting this model is discussed. This model is contrasted with alternative models based on late competition and with hybrid models. Finally, the role of attention in rivalry is examined and commonalities with other forms of bistable perception are noted. WIREs Cogn Sci 2012, 3:87-103. doi: 10.1002/wcs.151 For further resources related to this article, please visit the WIREs website.

Detecting contrast changes in invisible patterns during binocular rivalry

When dissimilar images are presented to the two eyes, the human visual system lapses into binocular rivalry, a unique perceptual state characterized by stochastic alternations in dominance of one of the two source images over the other. Probe targets delivered to an eye during suppression phases are more difficult to detect than probes delivered during dominance phases. Nearly all probe studies have involved presenting new stimulation (e.g., a spot of light) either superimposed on or replacing the suppressed stimulus. Here, we ask whether observers can detect a reduction in the contrast of the suppressed stimulus itself. In other words, can observers detect a probe that should make an already invisible stimulus even weaker? Specifically, we compared observers’ ability to detect contrast increments and contrast decrements introduced within a rival pattern during dominance and suppression. Contrast increment thresholds were elevated across all pedestal contrasts when the increment was introduced during suppression compared to during dominance, replicating previous results. Contrast decrement thresholds measured during suppression were elevated to an even greater extent, but the fact that they were obtained at all establishes that observers were able to detect probes that should make an already invisible target even more difficult to perceive. In a second experiment, we found a similar pattern of results for contrast change detection in complex images of faces as well. Based on the resulting threshold-vs.-contrast functions, we suggest that, regardless of the complexity of the image, rivalry suppression modulates the neural contrast response function through a mixture of reduced overall response gain and a shift in the contrast gain.

Feature-based attention enhances motion processing during dominance and suppression in binocular rivalry

Feature-based attention enhances motion processing during dominance and suppression in binocular rivalry

Saliency in a suppressed image affects the spatial origin of perceptual alternations during binocular rivalry

During binocular rivalry, perception alternates between dichoptically presented incompatible images. With larger images, such perceptual alternations will typically start locally and then gradually spread across the image, known as traveling waves of perceptual dominance. Several image-features (such as local contrast) are known to determine where in the image a traveling wave originates. Here we investigate whether orientation contrast in the suppressed image affects these spatial origin(s) of perceptual alternations. The results show that the origins are increasingly biased towards locations of increasing orientation contrast in the suppressed image. This increase in bias is related to the efficiency of visual search for the orientation contrast, tested offline: we find large biases towards orientation contrast when visual search for it is efficient, and small biases when search for it is inefficient. Our results imply that rivalry suppression is not homogenous across the suppressed image, but is dependent on local image-features in the suppressed image. The relation between spatial bias and visual search performance suggests that spatial origins of perceptual alternations are biased to salient locations in the suppressed image. Moreover, the finding that saliency affects the spatial origin of a perceptual alternation is in agreement with the idea that saliency is represented at a monocular, unconscious level of visual processing.

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.

Suppression during binocular rivalry broadens orientation tuning

During binocular-rivalry suppression, an ordinarily visible stimulus is erased from awareness, but how is the sensory representation of that stimulus affected? Although it is established that rivalry suppression attenuates signal strength, the influence of suppression on signal fidelity remains unknown. Here, we show that noise plays a hitherto undiscovered role in the degradation of the percept under suppression. In Experiment 1, we measured psychometric functions for a stimulus presented under dominance and suppression, and found that the slope of these functions was shallower under suppression—a result suggesting that the signal representation was rendered noisier. Experiment 2 then revealed the source of this noise: An examination of the influence of suppression on the orientation bandwidth of noise masking showed that tuning bandwidth is significantly broadened under suppression. Thus, the discriminability of a suppressed stimulus is weakened not only by a general decrease in signal strength, but als...

Single neuron responses in humans during binocular rivalry and flash suppression

Single neuron responses in humans during binocular rivalry and flash suppression

Contrast adaptation effects under interocualr suppression for normal and strabismic observers

Our vision system receives two different images from our two eyes. Since these two images usually have high correlation they are fused into a single stable image. In binocular rivalry suppression a stimulus presented in one eye is suppressed and a different stimulus in the other eye is perceived for a certain time interval. For strabismic observers the suppression is continuous between different retinal images caused by misalignment of eye positions. Previous research investigated the effects of this binocular rivalry suppression on a number of visual processes. The present study looked at the effects of contrast adaptation for the adaptation stimulus presented to eyes under interocular suppression. We compared normal and strabismic observers and found that in both types, regardless of the existence of suppression, there was the effect of contrast adaptation. These findings provide evidence that the suppression occurs at a site in the visual system after the locus of contrast adaptation. The contrast adaptation strength differed in the two types of observers.

Suppression during binocular rivalry broadens orientation tuning.

During binocular-rivalry suppression, an ordinarily visible stimulus is erased from awareness, but how is the sensory representation of that stimulus affected? Although it is established that rivalry suppression attenuates signal strength, the influence of suppression on signal fidelity remains unknown. Here, we show that noise plays a hitherto undiscovered role in the degradation of the percept under suppression. In Experiment 1, we measured psychometric functions for a stimulus presented under dominance and suppression, and found that the slope of these functions was shallower under suppression-a result suggesting that the signal representation was rendered noisier. Experiment 2 then revealed the source of this noise: An examination of the influence of suppression on the orientation bandwidth of noise masking showed that tuning bandwidth is significantly broadened under suppression. Thus, the discriminability of a suppressed stimulus is weakened not only by a general decrease in signal strength, but also by broader orientation tuning that introduces more noise in the neural representation of the suppressed stimulus.

Orientation-tuned suppression in binocular rivalry reveals general and specific components of rivalry suppression

During binocular rivalry (BR), conflicting monocular images are alternately suppressed from awareness. During suppression of an image, contrast sensitivity for probes is reduced by approximately 0.3-0.5 log units relative to when the image is in perceptual dominance. Previous studies on rivalry suppression have led to controversies concerning the nature and extent of suppression during BR. We tested for feature-specific suppression using orthogonal rivaling gratings and measuring contrast sensitivity to small grating probes at a range of orientations in a 2AFC orientation discrimination task. Results indicate that suppression is not uniform across orientations: suppression was much greater for orientations close to that of the suppressed grating. The higher suppression was specific to a narrow range around the suppressed rival grating, with a tuning similar to V1 orientation bandwidths. A similar experiment tested for spatial frequency tuning and found that suppression was stronger for frequencies close to that of the suppressed grating. Interestingly, no tuned suppression was observed when a flicker-and-swap paradigm was used, suggesting that tuned suppression occurs only for lower-level, interocular rivalry. Together, the results suggest there are two components to rivalry suppression: a general feature-invariant component and an additional component specifically tuned to the rivaling features.

Orientation-tuned suppression in binocular rivalry reveals general and specific components of rivalry suppression

Visually guided catch-up saccades during the pursuit of a moving target are highly influenced by smooth pursuit performance. For example, the decision to execute a saccade and its amplitude is driven by the difference in velocity between the eye and the target. In previous studies, we have demonstrated that the predictive saccades that occur during the blanking of the moving target compensate for the variability of the smooth pursuit response. Therefore, we wondered whether the predictive smooth pursuit response during target blanking influenced the occurrence of predictive saccades, which is the case for visually guided catch-up saccades. To answer this question, we asked subjects to track visually a target moving along a circular path. From time to time, the target was unexpectedly blanked for some randomized durations and disappeared from the screen. Surprisingly, we did not find any differences in smooth pursuit performance between the blanks that did and those that did not contain predictive saccades. In addition, during the blanks, the differences in smooth pursuit performance across the sessions or across the subjects did not correlate with the differences in the number of predictive saccades. Therefore, this study demonstrates that smooth pursuit performance does not influence the occurrence of predictive saccades. We interpret these results in light of the possible minimization of position error at target reappearance, which heavily depends on the saccadic amplitudes but not on their timing.

Motion streaks in fast motion rivalry cause orientation-selective suppression

We studied binocular rivalry between orthogonally translating arrays of random Gaussian blobs and measured the strength of rivalry suppression for static oriented probes. Suppression depth was quantified by expressing monocular probe thresholds during dominance relative to thresholds during suppression. Rivalry between two fast motions or two slow motions was compared in order to test the suggestion that fast-moving objects leave oriented "motion streaks" due to temporal integration (W. S. Geisler, 1999). If fast motions do produce motion streaks, then fast motion rivalry might also entail rivalry between the orthogonal streak orientations. We tested this using a static oriented probe that was aligned either parallel to the motion trajectory (hence collinear with the "streaks") or was orthogonal to the trajectory, predicting that rivalry suppression would be greater for parallel probes, and only for rivalry between fast motions. Results confirmed that suppression depth did depend on probe orientation for fast motion but not for slow motion. Further experiments showed that threshold elevations for the oriented probe during suppression exhibited clear orientation tuning. However, orientation-tuned elevations were also present during dominance, suggesting within-channel masking as the basis of the extra-deep suppression. In sum, the presence of orientation-dependent suppression in fast motion rivalry is consistent with the "motion streaks" hypothesis.

Conditions required for binocular rivalry suppression

When the two eyes are presented with incompatible stimuli, the two monocular stimuli are seen alternately in a never-ending cycle. It is now widely accepted that the neural processes underlying this phenomenon, binocular rivalry, are distributed across a number of cortical stages. It is not clear, however, where binocular rivalry is initiated. We performed two experiments whose aim was to clarify this issue. In the first experiment, rivalry was induced, and brief test stimuli were delivered to an eye while its inducing stimulus was either dominant or suppressed. Sensitivity to a test stimulus with features similar to those of the suppressed inducing stimulus was reduced only when the test was presented to the eye whose inducing stimulus was suppressed. This indicates that suppression of a monocular channel is a prerequisite for binocular rivalry suppression. The second experiment showed that to induce rivalry, local interocular stimulus incompatibilities were necessary and that conflicting global percepts were not sufficient. These results suggest that low-level visual processes are required for the initiation of binocular rivalry.

Attention-based perceptual learning increases binocular rivalry suppression of irrelevant visual features

Perceptual learning refers to an improvement on a perceptual task after repeated exposure to a stimulus. It has been shown that attention can play an important role in perceptual learning. Recently, it has been suggested that training can lead to increased suppression of information that is continuously irrelevant, and that this attention-based suppression plays an important role in more efficient noise exclusion. Here we investigate this claim. Observers performed a visual speed-discrimination task for 5 consecutive days. After training, sensitivity to motion directions that were relevant, irrelevant, or neutral toward the training task was assessed by measuring motion coherence thresholds. In addition, perceptual dominance during binocular rivalry was assessed for combinations of the three motion directions. The results showed that sensitivity to the task-relevant feature increased due to training. That is, motion coherence thresholds were selectively lowered for the task-relevant feature. Interestingly, the feature that was task-irrelevant during training was more strongly suppressed during binocular rivalry: The mean perceptual dominance of this feature was selectively decreased. Our results show that task-irrelevant information that potentially interferes with the primary task during learning gets more strongly suppressed. Furthermore, our results add new evidence in support of the claim that mechanisms involved in visual attention and binocular rivalry overlap.

Effect of binocular rivalry suppression on initial ocular following responses

To study the effect of binocular rivalry (BR) suppression on the ocular following response (OFR), we recorded the OFR in both the suppressed and the dominant phases of BR. The BR was established using stationary horizontal/vertical grating patterns presented on two PC monitors. Once a subjective image of a vertical or horizontal grating pattern was perceived, subjects pressed a button to trigger an onset of brief horizontal movement (750 ms) of the vertical grating pattern and an offset of the horizontal pattern. The OFRs were recorded using a scleral search coil system at 1 kHz. The OFRs from the suppressed phases were significantly reduced compared to those from the dominant phases. The OFRs were asymmetrical to temporalward and nasalward motion in most conditions. We suggest that asymmetry of OFRs under the incomplete BR conditions may be a reflection of imbalance binocular inputs and processing in the visual system similar to asymmetrical optokinetic nystagmus in strabismic subjects. The latency of the OFR in deeper suppressed conditions was prolonged, suggesting that the interaction of BR and OFR may occur at multiple stages including an early stage of the visual processing. The OFR may have the potential for objective measurement of BR suppression in clinical evaluation of binocular function.

Dynamics of perceptual filling-in of visual phantoms revealed by binocular rivalry

How do selective and constructive visual mechanisms interact to determine the outcome of conscious perception? Binocular rivalry involves selective perception of one of two competing monocular images, whereas visual phantoms involve perceptual filling-in between two low-contrast collinear gratings. Recently, we showed that visual phantoms lead to neural filling-in of activity in V1 and V2, which can be dynamically gated by rivalry suppression (M. Meng, D. A. Remus, & F. Tong, 2005). Here, we used psychophysical methods to study the temporal dynamics of filling-in, by applying rivalry or flash suppression to trigger the suppression or appearance of visual phantoms. Experiments revealed that phantom filling-in involves an active, time-dependent process that depends on the phenomenal visibility of the phantom-inducing gratings. Shortly after the inducing gratings became dominant during rivalry, the likelihood of perceiving phantoms in the intervening gap increased over time, with larger gaps requiring more time for filling-in. In contrast, suppression of the inducing gratings promptly led to the disappearance of visual phantoms, with response times independent of gap size. The fact that binocular rivalry can prevent the formation of visual phantoms rules out the possibility that rivalry suppression occurs after the site of phantom filling-in. This study provides novel evidence that visual phantoms result from a slow time-dependent filling-in mechanism; possible models to account for its time course are discussed.

Flash suppression and flash facilitation in binocular rivalry

We show that previewing one half image of a binocular rivalry pair can cause it to gain initial dominance when the other half is added, a novel phenomenon we term flash facilitation. This is the converse of a known effect called flash suppression, where the previewed image becomes suppressed upon rivalrous presentation. The exact effect of previewing an image depends on both the duration and the contrast of the prior stimulus. Brief, low-contrast prior stimuli facilitate, whereas long, high-contrast ones suppress. These effects have both an eye-based component and a pattern-based component. Our results suggest that, instead of reflecting two unrelated mechanisms, both facilitation and suppression are manifestations of a single process that occurs progressively during presentation of the prior stimulus. The distinction between the two phenomena would then lie in the extent to which the process has developed during prior stimulation. This view is consistent with a neural model previously proposed to account for perceptual stabilization of ambiguous stimuli, suggesting a relation between perceptual stabilization and the present phenomena.

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.

Central factors contributing to para-contrast modulation of contour and brightness perception

Following up on a prior study of contour and brightness processing in visual masking (Breitmeyer et al., 2006), we investigated the effects of a binocular and dichoptic para-contrast masking on the visibility of the contour and brightness of a target presented to the other eye. Combined, the results support the contributions of several cortical processes to para-contrast: (1) two central sources of inhibition, one long-latency and prolonged and the other short-latency and brief; (2) binocular rivalry suppression; and (3) a facilitatory effect peaking at different SOAs for the contour and the brightness tasks, reflecting; (4) known properties of two separate cortical systems, one a fast contour-processing pathway and the other a slower brightness-processing pathway.