Effects of stimulus size and contrast on binocular rivalry in adults with anisometropic amblyopia.

Multistable perceptual phenomena provide insights into the mind's dynamic states within a stable external environment, and the neural underpinnings of these consciousness changes are often studied with binocular rivalry (BR). Conventional methods to study binocular rivalry suffer from biases and assumptions that limit their ability to describe the continuous nature of these perceptual transitions and to discover what kind of percept was perceived across time. Recently, we developed a new method to avoid those shortcomings, called InFoRM-Rivalry. The method builds customized regions of six principal perceptual categories that are described in the literature, including two exclusive and four mixed perceptual categories, i.e. piecemeal (one) and superimposition (three). We re-analysed data using unsupervised clustering to determine where within these principal categories clusters of perception naturally occur. We show that, on average, 10 ± 8 categories arise and that these categories map predominately onto the exclusive and superimposed principal regions regardless of the stimulus contrast configurations. Next, we estimated the most likely transition pathways during binocular rivalry using a Hidden Markov model and showed that transitions are most likely to appear between monocular exclusive and binocular superimposed categories. These results suggest that binocular rivalry, triggered by low-level grating stimuli, involves conflict between monocular and binocular neural processing sites rather than only mutual inhibition of monocular sites.

The neural response of the prefrontal cortex varies with the color difference in binocular rivalry: Evidence from fNIRS.

No-reference stereoscopic image quality assessment (NR-SIQA) remains a fundamental challenge due to the complex biological mechanisms of binocular rivalry and fusion, particularly under asymmetric distortions. In this paper, we propose a novel framework termed Multi-Stage Complementary Ensemble (MSCE). The core innovation lies in the Adaptive Selective Propagation (ASP) strategy embedded within a hierarchical Transformer architecture to dynamically regulates the fusion of binocular features. Specifically, by simulating the human visual system's transition from binocular rivalry to fusion, the ASP strategy applies nonlinear gain control to selectively reinforce features from the governing view based on binocular discrepancies. Furthermore, the proposed Hierarchical Complementary Fusion (HCF) module effectively captures and integrates low-level texture integrity, mid-level structural degradation, and high-level semantic consistency, leveraging ensemble learning principles, within a unified quality-aware manifold. Experimental results on four benchmark datasets demonstrate that the MSCE framework achieves state-of-the-art performance, particularly in terms of prediction consistency under complex asymmetric distortions.

Binocular rivalry occurs when two eyes are presented with two conflicting stimuli. Although the physical stimulation stays the same, the conscious percept changes over time. This property makes it a unique paradigm in both vision science and consciousness research. Two key parameters, contrast and attention, were repeatedly shown to affect binocular rivalry dynamics in a similar manner. This was taken as evidence that attention acts by enhancing effective stimulus contrast. Brief transition periods between the two clear percepts have so far been much less investigated. In a previous study we demonstrated that transition periods can appear in different forms depending on the stimulus type and the observer. In the current study, we investigated how attention and contrast affect transition appearance. Observers viewed binocular rivalry and reported their perception of the four most common transition types by a button press while either the stimulus contrast or the locus of exogenous attention was manipulated. We show that contrast and attention similarly affect the overall binocular rivalry dynamics, but their effects on the appearance of transitions differ. These results suggest that the effect of attention is different from a simple enhancement of stimulus strength, which becomes evident only when different transition types are considered.

Continuous flash suppression (CFS) is a variant of interocular conflict that occurs when one eye views a dynamic high-contrast mask that increases the duration of target suppression. A variant of CFS known as tracking continuous flash suppression (tCFS) was developed, allowing the depth of interocular suppression to be measured. Although previous research has measured how the duration of suppression may be modulated by the contrast and size of the masking stimulus, no study has assessed how mask features impact suppression depth. In our first study, we manipulated mask contrast to measure the consequent impact on suppression depth as measured by the tCFS procedure. We observed that high mask contrast increased the threshold required for a target to break into awareness. Critically, the decrease in contrast required to re-suppress each target was proportionately the same across all conditions so that suppression depth—the ratio of the two thresholds—remained constant. In the second experiment, we manipulated the size of the masking stimulus and found no change in breakthrough/suppression thresholds or suppression depth (i.e., the difference between the thresholds when using log-contrast). These findings clarify that, although changes in mask contrast may alter the threshold to enter awareness, there is no overall change in suppression depth as the changes in breakthrough threshold are reflected by proportionately equivalent changes in suppression threshold. This result matches findings obtained with binocular rivalry showing that suppression depth is constant despite changes in stimulus contrast. Differing levels of mask contrast and size, therefore, can be used by researchers in CFS without altering the strength of suppression, consistent with the perspective that interocular suppression operates in small local spatial zones determined by receptive field size in the primary visual cortex.

Our visual system usually provides a unique and functional representation of the external world. At times, however, there is more than one compelling interpretation of the same retinal stimulus; in this case, neural populations compete for perceptual dominance to resolve ambiguity. Spatial and temporal context can guide this perceptual experience. Recent evidence shows that ambiguous retinal stimuli are sometimes resolved by enhancing either similarities or differences among multiple ambiguous stimuli. Although rivalry has traditionally been attributed to differences in stimulus strength, color vision introduces nonlinearities that are difficult to reconcile with luminance-based models. Here, it is shown that a tuned, divisive normalization framework can explain how perceptual selection can flexibly yield either similarity-based “grouped” percepts or difference-enhanced percepts during binocular rivalry. Empirical and simulated results show that divisive normalization can account for perceptual representations of either similarity enhancement (so-called grouping) or difference enhancement, offering a unified framework for opposite perceptual outcomes.

Visual rivalry paradigms provide a powerful tool for probing the mechanisms of visual awareness and perceptual suppression. Although the dynamics and determinants of perceptual switches in visual rivalry have been extensively studied and modeled, recent advances in experimental design—particularly those that quantify the depth and variability of perceptual suppression—have outpaced the development of computational models. Here we extend an existing dynamical model of binocular rivalry to encompass two novel experimental paradigms: a threshold detection variant of binocular rivalry, and tracking continuous flash suppression. Together, these tasks provide complementary measures of the dynamics and magnitude of perceptual suppression. Through numerical simulation, we demonstrate that a single mechanism, competitive (hysteretic) inhibition between slowly adapting monocular populations, is sufficient to account for the suppression depth findings across both paradigms. This unified model offers a foundation for the development of a quantitative theory of perceptual suppression in visual rivalry.

ABSTRACTBinocular rivalry (BR) occurs when each eye is presented with mutually incompatible images, and the brain alternates between perceiving one image, the other or occasionally a mashup of both. Addressing a decades‐old suggestion, it has been shown that the competition between alternative representations in BR induces a pattern of neural activation resembling that occurring in cognitive conflict, eventually leading to fluctuations between different perceptual outcomes in the case of steep competition. This is reflected by known signatures of conflict dynamics, namely, an increase in fronto‐medial theta oscillatory power (5–7 Hz) in the EEG right before perceptual transitions and a decrease thereafter, as well as a decrease in parieto‐occipital alpha oscillatory power (8–12 Hz) prior to perceptual transitions and an increase thereafter. However, according to a growing body of research, frontal activity during BR might be related to report processes rather than perception processing per se. Such conflation is related to the use of continuous report protocols. To circumvent this confound, here, we present a BR study using an onset rivalry (rather than continuous rivalry) protocol that dissociates the moment of report from the period of stimulus presentation. The findings revealed higher fronto‐medial theta power for rivalrous than for non‐rivalrous stimuli both resulting in equivalent perceptual classification, despite the absence of a motor confound. In addition, we found greater parieto‐occipital alpha suppression for rivalrous stimuli. The results presented here advance our understanding of how cognitive conflict monitoring and resolution may influence perception in the event of competition from incompatible sensory patterns.

ABSTRACT Color information plays a key role in cognitive regulation and the allocation of attentional resources. However, the influence of binocular color rivalry on prefrontal cortex (PFC) activation has not been systematically investigated. To address this, we employed functional near‐infrared spectroscopy (fNIRS) to examine oxygenated hemoglobin (HbO) responses in the PFC elicited by four binocular rivalry color pairs: red‐green (R‐G), yellow‐blue (Y‐B), orange‐cyan (RY‐GB), and purple‐yellow green (RB‐YG). The results showed that all color pairs induced significant activation in the PFC, particularly in Brodmann areas 9 (BA9) and 10 (BA10). The R‐G condition activated both regions, whereas Y‐B primarily activated BA10. Further regression analysis revealed significant differences in the activation patterns of L, M, and S cone cells across the color pairs, which were positively correlated with changes in HbO concentration in the PFC. In summary, this study reveals the hemodynamic response characteristics of the PFC during binocular color rivalry and their association with retinal cone activation, providing novel empirical evidence for understanding the neural mechanisms underlying visual rivalry.

Continuous flash suppression (CFS) is a popular method for suppressing visual stimuli from awareness for extended periods. It involves a dynamic, high-contrast masking stimulus presented to one eye that suppresses a target stimulus presented to the other. The strength of suppression is usually inferred from how long it takes for the target to break through from suppression into awareness (the bCFS threshold). A new variant known as tracking CFS (tCFS) directly measures the strength of suppression by measuring both breakthrough and suppression thresholds. Here, we employed the tCFS paradigm while varying the temporal frequency of the masking stimulus. Our data revealed two clear results: (a) CFS exhibits a clear temporal frequency tuning, with bCFS thresholds peaking for masks modulating at ∼1 Hz; and (b) suppression depth (the difference between breakthrough and suppression thresholds) remains constant despite changes in bCFS. The first result confirms an earlier finding that peak bCFS occurs for very low temporal frequencies. The second result provides valuable insight in showing that bCFS changes occur completely independently of suppression strength, which remains constant. In this study, suppression averaged 13 dB, around two to three times stronger than suppression reported in binocular rivalry studies.

Multisensory information can help resolve perceptual ambiguity in situations such as the alternating visual experience during binocular rivalry. Across four experiments, participants viewed dichoptically presented spiky and round rival targets while simultaneously touching spiky, neutral, or round shapes in three-dimensional (3D) printed form. The primary aim was to investigate the influence of visuotactile shape congruence in the curvature dimension. In addition, the roles of voluntary action and spatial colocalization on successful crossmodal integration were investigated. Voluntary action was tested between active touch (Experiments 1 and 2) and passive touch (Experiments 3 and 4) conditions. Visual stimulus type differed between rapid successions of 3D-rendered images (Experiments 1 and 3) and real-world video recordings (Experiments 2 and 4), with the latter involving bodily cues to promote visuotactile colocalization. In general, the results showed that tactile shape congruence can lead to relative dominance of the corresponding visual target, especially when visuotactile colocalization was encouraged with video recordings as visual targets. The results suggest beneficial effects of crossmodal shape congruence on disambiguation, which seems to be generally comparable between the two modes of active versus passive touch. Using 3D stimuli and including free voluntary action, the study provides novel and connecting insights into the naturalistic object processing behavior of humans.

Conscious perception, a critical aspect of human cognition, is assumed to emerge from a complex network of interacting brain regions that transmit information via feedforward and recurrent pathways. This study presents single- and multiunit recordings from the human lateral occipital complex (LO), a key region for shape and object recognition, during three distinct perceptual paradigms: backward masking, flash suppression and binocular rivalry. Stimulus awareness increased decoding accuracy and decoders assigned higher probabilities to the consciously perceived stimulus during periods of dichoptic stimulus presentation. These findings highlight the intricate neural mechanisms underlying visual awareness and show that LO responses predominantly align with subjective phenomenology, offering new insights into the neural correlates of visual consciousness.

Background: Opioid use disorder (OUD) and associated overdose deaths have reached epidemic proportions worldwide over the past two decades, with death rates for men consistently reported at twice the rate for women. We have recently reported sex-specific differences in electrocortical activity in persons with OUD in a visual object recognition task. The mesolimbic dopamine (DA) system is implicated in OUD but also plays a critical role in some disorders of visual attention and a modulatory role in the processing of visual stimuli in the blue cone pathway of the retina. We hypothesized that electrocortical responses to color stimuli would be affected differentially in men and women with OUD. Methods: Using a controlled, cross-sectional, age-matched (18-56 years) design, we evaluated color processing in male and female subjects recruited from a community-based, high-intensity residential substance abuse and detoxification treatment program. We evaluated electroencephalogram (EEG) event-related potentials (ERPs) and reaction time (RT), in male and female participants with OUD (n = 38) vs. sex- and age-matched non-OUD control participants (n = 37) in a simple color recognition Go/No-Go task, as well as perceptual and behavioral responses in physiological and neuropsychological tests. Results: N200, P300, and late potential (LP) Relevant stimulus-induced ERPs were evoked by the task and were well-differentiated from Irrelevant distractor stimuli. P300 amplitudes were significantly greater and N200 and LP latencies were significantly shorter in male vs. female non-OUD controls in this task. There were significant sex differences in N200, P300, and LP amplitudes and latencies between male vs. female non-OUD subjects and OUD differences with blue color as the Relevant stimulus. In the Binocular Rivalry Test, there were shorter dwell times for perceiving a blue stimulus in male OUD subjects and there were significant sex and OUD differences in neuropsychological tests including Finger Tapping, Trails A/B, and Symbol Digit Modalities Test. Conclusions: These findings suggest that there are significant sex-related physiological, perceptual, and cognitive differences in color processing that may result from deficits in DA production in the retina that mirror deficits in mesolimbic DA transmission correlating with OUD, suggesting that blue color processing has the potential to be an effective biomarker for brain DA and for diagnosis and monitoring of treatment efficacy in substance use disorders.

Purpose: Ocular dominance can be measured by a variety of tests, which may not yield the same results. This study compared the repeatability and agreement for two ocular dominance tests, a newer letter dominance test and a well-established binocular rivalry test.Methods: Thirty-nine adults (28 females and 11 males) with normal vision completed three sessions involving letter dominance and the binocular rivalry tests. An additional seven participants completed only one session. Within-test repeatability was assessed through intraclass correlation and standard deviation. Between-tests agreement was assessed through a Bland-Altman test, intraclass correlation, and ocular dominance directions.Results: Within-test analysis indicated that the letter dominance test had better repeatability than the grating rivalry test (intraclass correlation coefficient: letter dominance 0.829, rivalry 0.790; standard deviation: letter dominance 0.015 [median], rivalry 0.023 [median], P = .015). Between-test analysis indicated that the two tests had moderate to good agreement (intraclass correlation coefficient 0.712) and identified the same eye as dominant for most participants, although not all (39 consistent across tests, seven inconsistent when a strict measure of equidominance was adopted).Conclusion: These analyses indicate that the letter dominance test is a more repeatable measure of ocular dominance than the grating rivalry test, and that ocular dominance magnitude metrics do vary across tests.

How does the human brain resolve conflicts in sensory input to generate conscious perception? Using high-resolution 7 T functional MRI, we addressed this question by investigating column- and layer-specific activity in cortical and subcortical regions in humans during binocular rivalry. The results show that eye-specific rivalry arises from interocular inhibition between adjacent ocular dominance columns in the superficial layers of the primary visual cortex, but not between ocular layers of the lateral geniculate nucleus of the thalamus. Eye-specific feedback from the intraparietal sulcus plays an active role in biasing and synchronizing local competitions in the primary visual cortex into perceptually coherent representations, even without awareness of eye-of-origin information. These findings reveal the mesoscale mechanisms of perceptual conflict resolution in humans: local conflicts in sensory input are resolved by inhibitory microcircuits in the sensory cortex, while feedback signals from the parietal attention network bias and integrate local competitions into unified conscious perception.

ABSTRACT The human brain optimises cognitive resource allocation to enhance the processing speed and efficiency of vital information for better survival and adaptation in response to threat signals. Previous studies found that fearful expressions, as visual cues signalling threats, can not only have advantages in entering and remaining in awareness, but also enhance subsequent perceptual processing of low-spatial-frequency (LSF) information. However, it remains unknown whether the enhanced perceptual processing of LSF induced by fearful expressions also grants LSF information a competitive advantage in awareness. To this end, we employed a binocular rivalry paradigm to measure awareness of Gabor patches with low or high spatial frequencies following the rapid priming of fearful versus neutral expressions. The results revealed that the relative dominance of LSF over high-spatial-frequency (HSF) Gabor patches was markedly heightened following brief exposure to fearful compared with neutral expressions. This effect was found for both upright and inverted expressions, indicating it is independent of face configuration. Our study thus suggests a feature-based perceptual optimisation mechanism with evolutionary significance, potentially optimising cognitive resource allocation in threatening situations.

Stimulus-driven rivalry among V1 neurons.

Stable Traits, Adaptive Brains: links between Visual Homeostatic Plasticity and Personality.

Affective stimuli, such as fearful faces, are assumed to receive prioritized processing over neutral stimuli, making them easier to detect when perception is suppressed using techniques such as visual masking or binocular rivalry. Moreover, some studies suggest that fearful expressions can be processed outside of conscious awareness, as evidenced by enhanced early event-related potentials (ERPs) in response to subliminally presented fearful vs. neutral faces. This might be associated with increased detection of fear-related stimuli. However, it remains unclear whether increased cortical processing of unseen fearful faces is a necessary condition for detection advantages and whether effects are related to expression-related or low-level features of stimuli. In the present pre-registered ERP study, we addressed these questions using stereoscopic forward masking (FM). Forty-eight male and female participants were presented with fearful and neutral, intact and phase-scrambled faces. The behavioural results showed that masked fearful faces were detected better than neutral faces. Phase-scrambled faces did not show this effect, indicating that the perceptual advantage was not mediated by low-level spectral stimulus properties. ERPs elicited by consciously perceived faces showed typical expression effects in the form of enhanced occipito-temporal negativities in the time range of the N170 and the early posterior negativity (EPN). Crucially, these effects were absent for subjectively invisible faces, as corroborated by Bayesian statistics. Taken together, our results suggest that the perceptual advantage of fearful faces under dichoptic FM cannot be attributed to low-level stimulus properties. Furthermore, within this paradigm, the perceptual advantage does not coincide with the amplification of early ERPs to subjectively invisible faces, suggesting a dissociation between unconscious stimulus processing and stimulus detection.