Rival Target Research Articles

Shape congruence modulates visuo-haptic interactions during binocular rivalry

When two dissimilar images are presented to the corresponding retinal positions of the two eyes, perception alternates between the two images (Blake & Logothetis, 2002). Dubbed binocular rivalry (BR), this paradigm provides a window into inferential visual processing. Recent experiments using multisensory stimuli found that tactile information boosts the dominance of the congruent visual stimulus (Lunghi et al., 2010; Suzuki et al., 2019). The present study examines whether dynamic haptic exploration of 3D shape objects boosts the perception of congruent visual shape stimuli during BR. 3D spiky and round shapes were created with a parametric shape model (Gielis, 2003). The coordinates for the neutral shape were acquired through linear interpolation of round and spiky shape coordinates (Kwak et al., VSS 2018). Visual and haptic stimuli were each created by 3D rendering and 3D printing the shape models. Participants viewed a pair of rotating round and spiky shapes as rival targets while exploring haptic objects with their left hand. They used their right hand to track perceptual dominance via computer key press. There were four haptic conditions - three exploring round, spiky, and neutral shape objects and one with no haptic stimulation (visual-only). Visual dominance durations for each condition were normalized with the mean duration of visual-only trials to account for individual differences. Analyses showed significant differences in the normalized dominance durations of both round and spiky visual targets when exploring haptic stimuli of different shapes. Specifically, haptic exploration of an object was associated with increased dominance of the corresponding visual target for both round and spiky shape during BR. With these results based on stimuli parametrically modulated in a single shape dimension of curvature, we suggest that shape congruence between visual and haptic modalities boosts the dominance of the corresponding visual target.

The influence of sexual orientation on reputational punishment of other women’s behaviour

ABSTRACT The denigration of competitors is an evolved strategy used to give the impression that a rival is less appealing. Evidence indicates that women denigrate other women principally on appearance and sexual fidelity because men value these qualities in partners. The current investigation examined whether indirect aggression – the spreading of reputation-harming information about a rival woman – is a strategy utilised by both straight and lesbian women. Additionally, we explored whether it was influenced by the extent to which a rival target was identified as ‘threatening’ or sexually promiscuous. Female participants were assigned to one of two possible target vignette/photographic conditions (sexualised versus neutral) based on their self-identified sexual orientation. All were provided the same information about the target’s social life, asked whether they would share that information with others, and completed a threat assessment. Findings suggest that lesbian and straight women both use competitor derogation as a mating strategy and are more likely to denigrate targets they perceive as sexual rivals. Straight women reported a greater likelihood of conveying reputation-harming information about the target in the sexualised condition compared to the neutrally dressed condition, but dress did not influence lesbians’ likelihood of denigration. Potential differences in mate selection criteria are discussed.

Playing visual dominance of score on the piano: Skilled motor action matters in the awareness of musical notes during binocular rivalry, only when accompanied by auditory feedback

Previous studies in our group showed that a visual musical score viewed dichoptically with a radial grating enjoyed longer dominance durations when presented with an auditory melody congruent to that score (Kim et al., VSS 2014; Lee et al., 2015). It has also been reported that an action relevant to a visual interpretation contributes to resolve perceptual ambiguity during binocular rivalry (Beets et al., 2010; Maruya et al., 2007). In the present study, we investigated whether a skilled motor action linked tightly to one of the two rival targets affects audiovisual interaction during rivalry. Sixteen observers with varying degree of piano playing skill viewed dichoptically a musical score scrolling from right to left within a viewing window and a counter-phase flickering radial grating. The perceptual dominance of visual musical score was tracked by playing the musical notes on the midi keyboard, while the grating dominance was tracked by pressing a button on a computer keyboard. On "sound" trials, participants heard the sound of piano being played by themselves. On "no sound" trials, auditory feedback was not accompanied by keyboard playing. Results showed a positive correlation between the degree of piano playing skill and the normalized score-dominance durations, only when the auditory feedback was accompanied. Accordingly, observers were divided in two groups based on the skill. In the more-trained group (8.3 ±0.89 years in training, N=8), the normalized score-dominance durations with auditory feedback were distributed toward the longer side than without auditory feedback, while there was no such effect observed in the less-trained group (3.6 ± 0.56 years, N=8). These results suggest that an execution of skilled motor action closely linked to a visual stimulus has impact on the interaction between the visual stimuli and the auditory feedback during binocular rivalry, which relies on the mastery of the motor skill. Meeting abstract presented at VSS 2016

Perceptual dominance during binocular rivalry is prolonged by a dynamic surround

We examined whether dynamic stimulation that surrounds a rival target influences perceptual alternations during binocular rivalry. We presented a rival target surrounded by dynamic random-dot patterns to both eyes, and measured dominance durations for each eye's rival target. We found that rival target dominance durations were longer when surrounds were dynamic than when they were static or absent. Additionally, prolonged dominance durations were more apparent when the dynamic surround was alternately presented between the two eyes than when it was presented simultaneously to both eyes. These results indicate that dynamic stimulation that surrounds a rival target plays a role in maintaining the current perceptual state, and causes less perceptual alternations during binocular rivalry. Our findings suggest that dynamic signals on the retina may suppress rivalry, and thus provide useful information for stabilizing perceptions in daily life.

Color and Luminance Influence, but Can Not Explain, Binocular Rivalry Onset Bias

When an observer is presented with dissimilar images to the right and left eye, the images will alternate every few seconds in a phenomenon known as binocular rivalry. During sustained viewing, the timing of these switches appears to be unpredictable. Recent research has suggested that the initial ‘onset’ period of rivalry is not random and may be different in its neural mechanism than subsequent dominance periods. It is known that differences in luminance and contrast have a significant influence on the average dominance during sustained rivalry and that perception of luminance can vary between individuals and across the visual field. We therefore investigated whether perception of luminance contrast plays a role in onset rivalry. Observers viewed rival targets of equal brightness for brief presentations in eight locations of the near periphery and reported the color that was first dominant in each location. Results show that minimizing differences in brightness and contrast yields a stronger pattern of onset dominance bias and reveals evidence of monocular dominance. The results suggest that both contrast and monocular dominance play a role in onset dominance, though neither can fully explain the effect.

Attentional modulation of binocular rivalry.

Ever since Wheatstone initiated the scientific study of binocular rivalry, it has been debated whether the phenomenon is under attentional control. In recent years, the issue of attentional modulation of binocular rivalry has seen a revival. Here we review the classical studies as well as recent advances in the study of attentional modulation of binocular rivalry. We show that (1) voluntary control over binocular rivalry is possible, yet limited, (2) both endogenous and exogenous attention influence perceptual dominance during rivalry, (3) diverting attention from rival displays does not arrest perceptual alternations, and that (4) rival targets by themselves can also attract attention. From a theoretical perspective, we suggest that attention affects binocular rivalry by modulating the effective contrast of the images in competition. This contrast enhancing effect of top-down attention is counteracted by a response attenuating effect of neural adaptation at early levels of visual processing, which weakens the response to the dominant image. Moreover, we conclude that although frontal and parietal brain areas involved in both binocular rivalry and visual attention overlap, an adapting reciprocal inhibition arrangement at early visual cortex is sufficient to trigger switches in perceptual dominance independently of a higher-level “selection” mechanisms. Both of these processes are reciprocal and therefore self-balancing, with the consequence that complete attentional control over binocular rivalry can never be realized.

Peptide‐mediated cancer targeting of nanoconjugates

Targeted use of nanoparticles in vitro, in cells, and in vivo requires nanoparticle surface functionalization. Moieties that can be used for such a purpose include small molecules as well as polymers made of different biological and organic materials. Short amino acid polymers, peptides, can often rival target binding avidity of much larger molecules. At the same time, peptides are smaller than most nanoparticles and thus allow for multiple nanoparticle modifications and creation of pluripotent nanoparticles. Most nanoparticles provide multiple binding sites for different cargo and targeting peptides which can be used for the development of novel approaches for cancer targeting, diagnostics, and therapy. In this review, we will focus on peptides which have been used for the preparation of different nanoparticles designed for cancer research.

Does context influence a rival target's escape from suppression?

Does context influence a rival target's escape from suppression?

Periodic perturbations producing phase-locked fluctuations in visual perception

This paper describes a novel psychophysical and analytical technique, called periodic perturbation, for creating and characterizing perceptual waves associated with transitions in visibility of a stimulus during binocular rivalry and during binocular fusion. Observers tracked rivalry within a small, central region of spatially extended rival targets while small, brief increments in contrast ("triggers") were presented repetitively in antiphase within different regions of the two rival targets. Appropriately timed triggers produced entrainment of rivalry alternations within the central region, with the optimal timing dependent on an observer's native alternation rate. The latency between trigger and state switch increased with the distance between the location of the trigger and the central region being monitored, providing evidence for traveling waves of dominance. Traveling waves produced by periodic perturbation exhibited the same characteristics as those generated using a less efficient, more demanding discrete trial technique. We used periodic perturbation to reveal a novel relation between the dynamics associated with the spontaneous perceptual alternations and the speed of traveling waves across observers. In addition, we found evidence for traveling waves even when the events triggering them were initiated within regions of the visual field where binocular vision was stable, in the absence of binocular rivalry, implying that perceptual organization generally depends on spatio-temporal context.

Spatial spread of interocular suppression is guided by stimulus configuration.

When the two eyes view dissimilar monocular stimuli, the resulting interocular suppression can spread beyond the region of explicit stimulus conflict: portions of one rival target will disappear even though there is no competing stimulation at the corresponding location in the other eye's view. In a series of experiments we examined whether this spread of suppression is spatially isotropic or governed by the configuration of the stimulus a portion of which is subject to suppression. Observers reported the incidence of stimulus disappearance at different locations along or nearby the contours of a large figure, part of which was suppressed by presentation of a continuous flash-suppression stimulus to a restricted region of the other eye. For all observers, suppression spread over several degrees along the contours of the figure, but tended not to spread to locations nearby but disconnected from the figure. Suppression spread effectively over a smoothly curved contour, and it spread around a sharp corner defined by two abutting contours, albeit less effectively. Suppression tended not to spread to features within the interior of a figure (a face), even if those features formed an integral part of the figure. A gap within a spatially extended stimulus arrested the spread of suppression, unless that gap appeared to arise from occlusion. Spread of suppression was unrelated to sensory eye dominance and was found with a more conventional binocular rivalry configuration, too. These findings implicate the involvement of neural circuitry in which inhibition propagates along paths of excitation beyond spatial regions of explicit interocular conflict.

PERCEPTUAL EXPERIENCE AND TEMPORAL TWO STAGES IN FLASH SUPPRESSION FOR CONTOUR RIVALRY

The aim of this study was to determine if flash suppression for contour rivalry consisted of two subsequent stages that might be influenced by the observer's perceptual experience. Participant exposure to primes involved either simultaneous delivery of a grating among orthogonal gratings to both eyes (binocular priming) or to one eye alone (monocular priming) for 1 s. Interstimulus intervals (ISIs) of 0-2000 ms followed the prime, with rival target gratings then simultaneously presented to both eyes for 10-200 ms. When a stimulus-offset asynchrony (SOFFA) of 50 ms, observers dominantly perceived the unprimed target. With this selective effect, interocular transfer was noted for the monocular priming. When brief targets (10 ms) were employed, two temporal stages with less individuality were detected. When longer targets (200 ms) were used during the monocular priming, the experienced observers were better at preserving the visibility as compared to the naive observers.

ALTERATION OF INTEROCULAR SUPPRESSION FOLLOWING MONOCULAR HOMOGENEOUS STIMULUS

Flash suppression is a phenomenon of interocular suppression where a monocular prime is immediately followed by dichoptic rival targets, inducing dominance of the contralateral view. Studies examining flash suppression have shown that a prime with visual features provokes feature-selective suppression. This study employed a prime lacking any features and examined the effects on visibility of the dichoptic targets. The prime (homogeneous grey field; luminance, 3.0 cd/m2) was presented to one eye alone for 1000 ms, followed immediately by dichoptic rival targets (blue vs. red squares) for durations of 10–200 ms. Visible colors were contralateral to the prime for targets 50 ms. The results suggest that the net effect of flash suppression might be eye-specific and different from feature-selective suppression.

Adaptive center-surround interactions in human vision revealed during binocular rivalry

We used binocular rivalry as a psychophysical probe to explore center-surround interactions in orientation, motion and color processing. Addition of the surround matching one of the rival targets dramatically altered rivalry dynamics. For all visual sub-modalities tested, predominance of the high-contrast rival target matched to the surround was greatly reduced—a result that disappeared at low contrast. At low contrast, addition of the surround boosted dominance of orientation and motion targets matched to the surround. This contrast-dependent modulation of center-surround interactions seems to be a general property of the visual system and may reflect an adaptive balance between surround suppression and spatial summation.

Center–surround inhibition deepens binocular rivalry suppression

When dissimilar stimuli are presented to each eye, perception alternates between both images—a phenomenon known as binocular rivalry. It has been shown that stimuli presented in proximity of rival targets modulate the time each target is perceptually dominant. For example, presenting motion to the region surrounding the rival targets decreases the predominance of the same-direction target. Here, using a stationary concentric grating rivaling with a drifting grating, we show that a drifting surround grating also increases the depth of binocular rivalry suppression, as measured by sensitivity to a speed discrimination probe on the rival grating. This was especially so when the surround moved in the same direction as the grating, and was slightly weaker for opposed directions. Suppression in both cases was deeper than a no-surround control condition. We hypothesize that surround suppression often observed in area MT (V5)—a visual area implicated in visual motion perception—is responsible for this increase in suppression. In support of this hypothesis, monocular and binocular surrounds were both effective in increasing suppression depth, as were surrounds contralateral to the probed eye. Static and orthogonal motion surrounds failed to add to the depth of rivalry suppression. These results implicate a higher-level, fully binocular area whose surround inhibition provides an additional source of suppression which sums with rivalry suppression to effectively deepen suppression of an unseen rival target.

Color promotes interocular grouping during binocular rivalry

During binocular rivalry local image features distributed over space and between the eyes achieve simultaneous dominance at times; the resulting global figure implicates interocular grouping. Anecdotal evidence suggests that color tends to influence the incidence of global dominance, and in this study we have assessed the strength of this influence on interocular grouping. Experiment 1: We used rival targets like those created by Diaz-Caneja (1928): concentric semi-circles and parallel horizontal lines distributed between the eyes. Using both achromatic and colored versions of these targets, we measured the percentage of time a single coherent figure (e.g., a complete bullseye) was perceived (implicating interocular grouping). Color congruence significantly increased the incidence of interocular global dominance. Experiment 2: Knowing that different parts of an occluded object tend to be perceptually grouped, we manipulated both the color and the shape of partially occluded objects that comprised rival targets. Relative to results with achromatic figures, uniform color paired with shape coherence enhanced interocular grouping, while conflict between color and shape coherence reduced interocular grouping. Experiment 3: Prolonged adaptation to different colors paired with different orientations induces an orientation-contingent color aftereffect (the McCollough effect). Observers first alternately adapted to a red diagonal grating tilted clockwise and to a green diagonal grating tilted counterclockwise. Immediately after prolonged adaptation, observers tracked rivalry between rival figures consisting of achromatic diagonal lines that appeared colored owing to the McCollough effect. Illusory color promoted strong interocular grouping relative to preadaptation testing. Conclusion: Both real and illusory colors are potent contributors to interocular grouping during binocular rivalry.

A fresh look at interocular grouping during binocular rivalry

During binocular rivalry, observers sometimes perceive one complete visual object even though component features of that perceptually dominant object are distributed between the two eyes and are in rivalry against other, dissimilar features. This interocular grouping cannot be explained by models of rivalry in which one eye or the other is completely dominant at any given moment. But perhaps global interocular grouping is achieved by simultaneous local eye dominance, wherein portions of one eye’s view and complementary portions of the other eye’s view become dominant simultaneously. To test this possibility, we performed two experiments using relatively large, complex figures as rival targets. In one experiment we used an “eye-swap” technique to confirm that within given, local spatial regions of rivalry it was the region of an eye––not a given stimulus feature––that was usually dominant. In a second experiment, we measured dominance durations for multiple, local zones of rivalry and then created 1-min animations of a global “montage” in which dominance within local regions was governed by the distributions of dominance measured empirically. These animations included significant periods of time during which global interocular grouping was evident; observers viewed these animations intermixed with actual rivalry displays, and the resulting tracking data confirmed the similarity in global dominance of the two display types. Thus interocular grouping during rivalry does not rule out local, eye-based rivalry, although synergistic and top-down influences almost certainly provide additional force in the promotion of interocular grouping.

Visual Motion Retards Alternations between Conflicting Perceptual Interpretations

When the visual system is faced with conflicting or ambiguous stimulus information, visual perception fluctuates over time. We found that perceptual alternations are slowed when inducing stimuli move within the visual field, constantly engaging fresh, unadapted neural tissue. During binocular rivalry, dominance durations were longer when rival figures moved compared to when they were stationary, yielding lower alternation rates. Rate was not reduced, however, when observers tracked the moving targets, keeping the images on approximately the same retinal area. Alternations were reliably triggered when rival targets passed through a local region of the visual field preadapted to one of the rival targets. During viewing of a kinetic globe whose direction of rotation was ambiguous, observers experienced fewer alternations in perceived direction when the globe moved around the visual field or when the globe's axis of rotation changed continuously. Evidently, local neural adaptation is a key ingredient in the instability of perception.

V1 activity is reduced during binocular rivalry.

During binocular rivalry, one of two incompatible monocular stimuli is erased from perceptual awareness for seconds at a time. To examine whether this "rivalry suppression" occurs in V1, we measured functional magnetic resonance imaging activity during binocular rivalry and compared it with those in the two reference conditions: one representing complete suppression and the other representing no suppression. We found that the amplitude of V1 activity during rivalry fell midway between those in the two reference conditions; the amount of V1 activity associated with the nondominant pattern was reduced by 48% to 77% during rivalry. The same pattern of results was obtained with meaningful rival targets (i.e., a human face and a house). In this work, using a different experimental protocol, we confirmed the findings of earlier imaging studies that neuronal events associated with binocular rivalry occur as early as V1. Furthermore, our findings extend those earlier findings by demonstrating robust neural suppression during binocular rivalry regardless of the stimulus complexity of the rivaling targets.

How context influences predominance during binocular rivalry.

Variations in the predominance of an object engaged in binocular rivalry may arise from variations in the durations of dominance phases, suppression phases, or both. Earlier work has shown that the predominance of a binocular rival target is enhanced if that target fits well-via common color, orientation, or motion-with its surrounding objects. In the present experiments, the global context outside of the region of rivalry was changed during rivalry, to learn whether contextual information alters the ability to detect changes in a suppressed target itself. Results indicate that context will maintain the dominance of a rival target, but will not encourage a suppressed target to escape from suppression. Evidently, the fate of the suppressed stimulus is determined by neural events distinct from those responsible for global organization during dominance. To reconcile diverse findings concerning rivalry, it may be important to distinguish between processes responsible for selection of one eye's input for dominance from processes responsible for the implementation and maintenance of suppression.

Grouping visual features during binocular rivalry

During binocular rivalry, portions of one eye’s view may be perceptually dominant while other portions are suppressed; at any given moment, overall dominance often resembles a patchwork mixture of the two eyes’ views. This study investigates the potency of two Gestalt grouping cues — good continuation and common fate — to promote synchronous fluctuations in dominance of two, spatially separated rival targets. Two grating patches were presented to the left eye paired dichoptically with random-dot patches presented to corresponding right eye locations. The orientations of the two gratings were either collinear, parallel or orthogonal. Gratings underwent contrast modulations that were either correlated (identical contrast changes) or uncorrelated (independent contrast changes). Over 60 s trials, observers pressed one key when the left grating predominated, another when the right grating predominated and both keys when both were concurrently visible. Correlated contrast modulation promoted joint grating predominance relative to the uncorrelated conditions, an effect strongest for collinear gratings. Joint predominance depended strongly on the angular separation between gratings and the temporal phase-lag in contrast modulations. These findings may reflect neural interactions subserved by lateral connections between cortical hypercolumns.