Motion-induced Blindness Research Articles

Stimulus strength and visual competition contribute to individual differences in Stroop-Task performance

Abstract The Stroop task is a popular test for measuring executive control. In this task subjects are shown words describing a color in a font color that mismatches its description. The word's meaning distracts and slows reaction times when subjects have to report the word's font color. This is called Stroop interference. Popular computational models of the Stroop task indicate that a competition between words and colors underlies Stroop interference. It is possible that some of the variance in Stroop interference across individuals may be explained by differences in visual pathway strength and differences in competition between stimulus categories, independent of executive control. We designed an electrophysiological and psychophysical experiment to examine the effects of these variables on Stroop interference. In experiment 1, observers were presented with words and colors in isolation and event-related potentials (ERP) were measured to determine relative visual pathway strength. In experiment 2, observers reported target disappearances caused by motion-induced blindness as an indication of the strength of competition in the visual system. Observers also performed the Stroop task after experiment 1 and 2. In experiment 1 we found that the relative latencies of the P3 ERP component to words and colors highly predicted Stroop interference (50% variance explained). Furthermore, in experiment 2 the strength of motion-induced-blindness also predicted Stroop interference (40% variance explained). In neither experiment, these effects could be explained by trial-to-trial fluctuations in cognitive control. Hence, we conclude that the Stroop effect is largely determined by an individual's pre-set characteristics in visual processing and competition between feature categories. Meeting abstract presented at VSS 2015.

Motion-induced blindness continues outside visual awareness and without attention.

Visual phenomena demonstrating striking perceptual disappearances of salient stimuli have fascinated researchers because of their utility in identifying neural processes that underlie subjective visibility and invisibility. Motion-induced blindness (MIB) is appealing for such purposes because it, like a class of ostensibly related paradigms such as binocular rivalry, features periods of unequivocal subjective disappearances despite constant physical stimulation. It remains unclear, however, exactly how the mechanisms that cause MIB are related to subjectively observed fluctuations in visual awareness. To address this question, we used continuous flash suppression (CFS) to present the MIB stimulus outside visual awareness. Results indicated that MIB occasionally reappeared from suppression with its salient yellow target absent. To quantify this observation, we measured reaction times (RTs) to detect the yellow dot target following visible or perceptually suppressed MIB and indeed found no difference in RTs between these conditions. We also provide evidence that MIB fluctuations can occur without attention. In sum, these experiments indicate that MIB fluctuations are effectively changes in stimulus strength, which under typical conditions result in unmistakable subjective disappearances, but are not inherently fluctuations in stimulus visibility. More broadly, these results challenge the assumed privileged link between bistable stimuli and visual awareness.

Pupil size tracks perceptual content and surprise.

Changes in pupil size at constant light levels reflect the activity of neuromodulatory brainstem centers that control global brain state. These endogenously driven pupil dynamics can be synchronized with cognitive acts. For example, the pupil dilates during the spontaneous switches of perception of a constant sensory input in bistable perceptual illusions. It is unknown whether this pupil dilation only indicates the occurrence of perceptual switches, or also their content. Here, we measured pupil diameter in human subjects reporting the subjective disappearance and re-appearance of a physically constant visual target surrounded by a moving pattern ('motion-induced blindness' illusion). We show that the pupil dilates during the perceptual switches in the illusion and a stimulus-evoked 'replay' of that illusion. Critically, the switch-related pupil dilation encodes perceptual content, with larger amplitude for disappearance than re-appearance. This difference in pupil response amplitude enables prediction of the type of report (disappearance vs. re-appearance) on individual switches (receiver-operating characteristic: 61%). The amplitude difference is independent of the relative durations of target-visible and target-invisible intervals and subjects' overt behavioral report of the perceptual switches. Further, we show that pupil dilation during the replay also scales with the level of surprise about the timing of switches, but there is no evidence for an interaction between the effects of surprise and perceptual content on the pupil response. Taken together, our results suggest that pupil-linked brain systems track both the content of, and surprise about, perceptual events.

Cross-modal prediction changes the timing of conscious access during the motion-induced blindness.

Despite accumulating evidence that perceptual predictions influence perceptual content, the relations between these predictions and conscious contents remain unclear, especially for cross-modal predictions. We examined whether predictions of visual events by auditory cues can facilitate conscious access to the visual stimuli. We trained participants to learn associations between auditory cues and colour changes. We then asked whether congruency between auditory cues and target colours would speed access to consciousness. We did this by rendering a visual target subjectively invisible using motion-induced blindness and then gradually changing its colour while presenting congruent or incongruent auditory cues. Results showed that the visual target gained access to consciousness faster in congruent than in incongruent trials; control experiments excluded potentially confounding effects of attention and motor response. The expectation effect was gradually established over blocks suggesting a role for extensive training. Overall, our findings show that predictions learned through cross-modal training can facilitate conscious access to visual stimuli.

Top-down modulation in human visual cortex predicts the stability of a perceptual illusion.

Conscious perception sometimes fluctuates strongly, even when the sensory input is constant. For example, in motion-induced blindness (MIB), a salient visual target surrounded by a moving pattern suddenly disappears from perception, only to reappear after some variable time. Whereas such changes of perception result from fluctuations of neural activity, mounting evidence suggests that the perceptual changes, in turn, may also cause modulations of activity in several brain areas, including visual cortex. In this study, we asked whether these latter modulations might affect the subsequent dynamics of perception. We used magnetoencephalography (MEG) to measure modulations in cortical population activity during MIB. We observed a transient, retinotopically widespread modulation of beta (12-30 Hz)-frequency power over visual cortex that was closely linked to the time of subjects' behavioral report of the target disappearance. This beta modulation was a top-down signal, decoupled from both the physical stimulus properties and the motor response but contingent on the behavioral relevance of the perceptual change. Critically, the modulation amplitude predicted the duration of the subsequent target disappearance. We propose that the transformation of the perceptual change into a report triggers a top-down mechanism that stabilizes the newly selected perceptual interpretation.

Fluctuations of visual awareness: combining motion-induced blindness with binocular rivalry.

Binocular rivalry (BR) and motion-induced blindness (MIB) are two phenomena of visual awareness where perception alternates between multiple states despite constant retinal input. Both phenomena have been extensively studied, but the underlying processing remains unclear. It has been suggested that BR and MIB involve the same neural mechanism, but how the two phenomena compete for visual awareness in the same stimulus has not been systematically investigated. Here we introduce BR in a dichoptic stimulus display that can also elicit MIB and examine fluctuations of visual awareness over the course of each trial. Exploiting this paradigm we manipulated stimulus characteristics that are known to influence MIB and BR. In two experiments we found that effects on multistable percepts were incompatible with the idea of a common oscillator. The results suggest instead that local and global stimulus attributes can affect the dynamics of each percept differently. We conclude that the two phenomena of visual awareness share basic temporal characteristics but are most likely influenced by processing at different stages within the visual system.

Spontaneous local alpha oscillations predict motion-induced blindness.

Bistable visual illusions are well suited for exploring the neuronal states of the brain underlying changes in perception. In this study, we investigated oscillatory activity associated with 'motion-induced blindness' (MIB), which denotes the perceptual disappearance of salient target stimuli when a moving pattern is superimposed on them (Bonneh et al., ). We applied an MIB paradigm in which illusory target disappearances would occur independently in the left and right hemifields. Both illusory and real target disappearance were followed by an alpha lateralization with weaker contralateral than ipsilateral alpha activity (~10 Hz). However, only the illusion showed early alpha lateralization in the opposite direction, which preceded the alpha effect present for both conditions and coincided with the estimated onset of the illusion. The duration of the illusory disappearance was further predicted by the magnitude of this early lateralization when considered over subjects. In the gamma band (60-80 Hz), we found an increase in activity contralateral relative to ipsilateral only after a real disappearance. Whereas early alpha activity was predictive of onset and length of the illusory percept, gamma activity showed no modulation in relation to the illusion. Our study demonstrates that the spontaneous changes in visual alpha activity have perceptual consequences.

Remote temporal camouflage: contextual flicker disrupts perceived visual temporal order.

Correctly perceiving the temporal order of events is essential to many tasks. Despite this, the factors constraining our ability to make timing judgments remain largely unspecified. Here we present a new phenomenon demonstrating that perceived timing of visual events may be profoundly impaired by the mere presence of irrelevant events elsewhere in the visual field. Human observers saw two abrupt luminance events presented across a range of onset asynchronies. Temporal order judgment (TOJ) just noticeable differences (JNDs) provided a behavioural index of temporal precision. When target events were presented in isolation or in static distractor environments temporal resolution was very precise (JNDs ∼20ms). However, when surrounded by dynamic distractor events, performance deteriorated more than a factor of four. This contextual effect we refer to as Remote Temporal Camouflage (RTC) operates across large spatial and temporal distances and possesses a unique spatial distribution conforming to neither the predictions of attentional capture by transient events, nor by stimulus dependencies associated with other contextual phenomena such as surround suppression, crowding, object-substitution masking or motion-induced blindness. We propose that RTC is a consequence of motion-related masking whereby irrelevant motion signals evoked by dynamic distractors interfere with TOJ-relevant target-related apparent motion. Consistent with this we also show that dynamic visual distractors do not interfere with audio-visual TOJs. Not only is RTC the most spatially extensive contextual effect ever reported, it offers vision science a new technique with which to investigate temporal order performance, free of motion-related sensory contributions.

Multistable Perception in Schizophrenia: A Model-based Analysis via Coarse-grained Order Parameter Dynamics and a Comment on the 4th Law

The synergetic computer that has originally been developed as an algorithm for pattern recognition has also been used in the life sciences as a model for various self-organizing perceptual processes. Coarse-graining of the order parameter equations of the synergetic computer is discussed for sets of to-be-perceived patterns that vary in the degree to which they can be distinguished from each other. Coarse-gaining is exploited to conduct a model-based analysis on literature data of multistable perception under schizophrenia as tested in motion-induced blindness (MIB) experiments. The analysis not only supports earlier suggestions that schizophrenia reduces the occurrence frequency of the MIB effect but also suggests that the perceptual system of schizophrenia patients is characterized by a greater degree of asymmetry.

Correction: Motion-Induced Blindness and Troxler Fading: Common and Different Mechanisms

Correction: Motion-Induced Blindness and Troxler Fading: Common and Different Mechanisms

Motion-Induced Blindness and Troxler Fading: Common and Different Mechanisms

Extended stabilization of gaze leads to disappearance of dim visual targets presented peripherally. This phenomenon, known as Troxler fading, is thought to result from neuronal adaptation. Intense targets also disappear intermittently when surrounded by a moving pattern (the “mask”), a phenomenon known as motion-induced blindness (MIB). The similar phenomenology and dynamics of these disappearances may suggest that also MIB is, likewise, solely due to adaptation, which may be amplified by the presence of the mask. Here we directly compared the dependence of both phenomena on target contrast. Observers reported the disappearance and reappearance of a target of varying intensity (contrast levels: 8%–80%). MIB was induced by adding a mask that moved at one of various different speeds. The results revealed a lawful effect of contrast in both MIB and Troxler fading, but with opposite trends. Increasing target contrast increased (doubled) the rate of disappearance events for MIB, but decreased the disappearance rate to half in Troxler fading. The target mean invisible period decreased equally strongly with target contrast in MIB and in Troxler fading. The results suggest that both MIB and Troxler are equally affected by contrast adaptation, but that the rate of MIB is governed by an additional mechanism, possibly involving antagonistic processes between neuronal populations processing target and mask. Our results link MIB to other bi-stable visual phenomena that involve neuronal competition (such as binocular rivalry), which exhibit an analogous dependency on the strength of the competing stimulus components.

Motion-induced blindness is influenced by global properties of the moving mask

Perceptual fluctuations experienced during motion-induced blindness (MIB) have been characterized as the result of a competition between representations of the moving mask and stationary (or slowly moving) targets (Bonneh, Cooperman, & Sagi, 2001). While there is evidence to support a local influence of the mask on target disappearance, what is not yet clear is whether the global properties of the mask can likewise impact disappearance. In the present study, we investigated the presence of a global effect of the mask on MIB by manipulating global motion properties of the mask while controlling its local motion properties surrounding the target. Results showed a significant impact of the global mask properties on the observed degree of disappearance. We also tested for a complementary local effect by comparing conditions in which we manipulated local mask properties while controlling global properties. This analysis did not yield evidence for a local effect, although this may have been due to our weaker manipulation of local mask properties compared to previous studies. Overall, the present results highlight a key role of global stimulus representations in producing the perceptual disappearances observed in MIB.

Interpreting the temporal dynamics of perceptual rivalries.

Diverse forms of perceptual rivalry are claimed to tap a common causal mechanism. One of the bases for this claim is that the reported dynamics of binocular rivalry and motion-induced blindness are similar on an individual basis (Carter & Pettigrew, 2003 Perception, 32, 295-305). We examined this relationship and found no evidence for a strong correlation. We therefore question the proposition that the dynamics of diverse forms of rivalry are driven by a common mechanism.

Opposing roles of sensory and parietal cortices in awareness in a bistable motion illusion

Motion-induced blindness (MIB) is a bistable visual phenomenon in which stationary disks surrounded by a moving pattern intermittently disappear from the viewer's awareness. We explored the cortical network that subserves the MIB phenomenon by targeting its constituent parts with disruptive transcranial magnetic stimulation (TMS), in the form of continuous theta burst stimulation (cTBS). Previous neuroimaging and TMS studies have implicated the right posterior parietal cortex (rPPC) in perceptual transitions such as binocular rivalry, while the visual area V5/MT has been suggested to play a key role in MIB. In this study, we found that cTBS applied to the rPPC lengthened the duration of disappearance in MIB, while cTBS applied to V5/MT shortened the duration of disappearance and decreased the frequency of disappearance in MIB. These results demonstrate a causal role for both the rPPC and V5/MT in MIB, and suggest that the rPPC is involved in shifting resources between competing functional areas, while V5/MT processing initiates and maintains MIB.

Motion-induced blindness without awareness or attention

Motion-induced blindness (MIB) distinctly visible stimuli are made to periodically disappear by placement within a moving pattern. MIB has been widely utilized to investigate the neural and cognitive mechanisms of visual awareness. We probed observers’ perceptual states after periods of MIB outside of awareness (suppressed by continuous flash suppression: CFS), unattended (concurrent rapid serial visual presentation task), or both. If the target fluctuates during these manipulations (without awareness and/or attention), it should sometimes be perceptually suppressed after this period due to MIB, resulting in longer reaction times (RT) to report the target. We found that CFS and/or inattention had no significant effect on RTs for target detection compared to normal MIB. This suggests that the dynamics of MIB were unaffected by removing awareness, attention or both. A baseline condition in which the target dot was physically absent during the manipulation period only, produced reliably faster RTs for all of our manipulations, including CFS. To ensure that target suppression was due to MIB and not CFS, we ran a stationery MIB control and found no effect of CFS. Together, these results suggest that the phenomenon of MIB is unaffected by the removal of awareness, attention, or both.

A Common Mechanism for Perceptual Reversals in Motion-induced Blindness, the Troxler Effect, and Perceptual Filling-In

Several striking visual phenomena involve a physically present stimulus that alternates between being perceived and being invisible. For example, motion-induced blindness, the Troxler effect, and perceptual filling-in all consist of subjective alternations where an item repeatedly changes from being seen to unseen. In the present study, we explored whether these three specific visual phenomena share any commonalities in their alternation rates and patterns to better understand the mechanisms of each. Data from 69 individuals revealed moderate to strong correlations across the three phenomena for the number of perceptual disappearances and the accumulated duration of the disappearances. Importantly, these effects were not correlated with eye movement patterns (saccades) assessed through eye tracking, differences in motion sensitivity as indexed by dot coherence and speed perception thresholds, or simple reaction time abilities. Principal component analyses revealed a single component that explained 67% of the variance for the number of perceptual reversals and 60% for the accumulated duration of the disappearances. The temporal dynamics of illusory disappearances was also compared for each phenomenon, and normalized durations of disappearances were well fit by a gamma distribution with similar shape parameters for each phenomenon, suggesting that they may be driven by a single oscillatory mechanism.

Congruence with items held in visual working memory boosts invisible stimuli into awareness: Evidence from motion-induced blindness

Congruence with items held in visual working memory boosts invisible stimuli into awareness: Evidence from motion-induced blindness

A Special Illusion: Motion-induced Blindness

A Special Illusion: Motion-induced Blindness

GABA Shapes the Dynamics of Bistable Perception

Sometimes, perception fluctuates spontaneously between two distinct interpretations of a constant sensory input. These bistable perceptual phenomena provide a unique window into the neural mechanisms that create the contents of conscious perception. Models of bistable perception posit that mutual inhibition between stimulus-selective neural populations in visual cortex plays a key role in these spontaneous perceptual fluctuations. However, a direct link between neural inhibition and bistable perception has not yet been established experimentally. Here, we link perceptual dynamics in three distinct bistable visual illusions (binocular rivalry, motion-induced blindness, and structure from motion) to measurements of gamma-aminobutyric acid (GABA) concentrations in human visual cortex (as measured with magnetic resonance spectroscopy) and to pharmacological stimulation of the GABAA receptor by means of lorazepam. As predicted by a model of neural interactions underlying bistability, both higher GABA concentrations in visual cortex and lorazepam administration induced slower perceptual dynamics, as reflected in a reduced number of perceptual switches and a lengthening of percept durations. Thus, we show that GABA, the main inhibitory neurotransmitter, shapes the dynamics of bistable perception. These results pave the way for future studies into the competitive neural interactions across the visual cortical hierarchy that elicit conscious perception.

Retinotopic Patterns of Correlated Fluctuations in Visual Cortex Reflect the Dynamics of Spontaneous Perceptual Suppression

While viewing certain stimuli, perception changes spontaneously in the face of constant input. For example, during "motion-induced blindness" (MIB), a small salient target spontaneously disappears and reappears when surrounded by a moving mask. Models of such bistable perceptual phenomena posit spontaneous fluctuations in neuronal activity throughout multiple stages of the visual cortical hierarchy. We used fMRI to link correlated activity fluctuations across human visual cortical areas V1 through V4 to the dynamics (rate and duration) of MIB target disappearance. We computed the correlations between the time series of fMRI activity in multiple retinotopic subregions corresponding to MIB target and mask. Linear decomposition of the matrix of temporal correlations revealed spatial patterns of activity fluctuations, regardless of whether or not these were time-locked to behavioral reports of target disappearance. The spatial pattern that dominated the activity fluctuations during MIB was spatially nonspecific, shared by all subregions, but did not reflect the dynamics of perception. By contrast, the fluctuations associated with the rate of MIB disappearance were retinotopically specific for the target subregion in V4, and the fluctuations associated with the duration of MIB disappearance states were target-specific in V1. Target-specific fluctuations in V1 have not previously been identified by averaging activity time-locked to behavioral reports of MIB disappearance. Our results suggest that different levels of the visual cortical hierarchy shape the dynamics of perception via distinct mechanisms, which are evident in distinct spatial patterns of spontaneous cortical activity fluctuations.