Distractor-induced Blindness Research Articles

Event-related potentials of stimuli inhibition and access in cross-modal distractor-induced blindness.

Distractor-induced blindness (DIB) describes a reduced access to a cued visual target-if multiple target-like distractors have been presented beforehand. Previous ERP data suggest a cumulative frontal inhibition triggered by distractors, which affects the updating process of the upcoming target. In the present study, we examine whether the modality of the cue-formerly defined in the visual domain-affects the expression of these neural signatures. 27 subjects were tested in a cross-modal DIB task: Distractors and targets were defined by a transient change of stimuli shape in a random-dot kinematogram. The onset of the target was announced by a rise in amplitude of a sinusoidal tone. Behavioral results confirmed that detection of the target relies on the number of preceding distractor episodes. Replicating previous unimodal results, ERP responses to distractors were characterized by a frontal negativity starting at 100 ms, which increases with an increasing number of distractor episodes. However, the processing-and detection-of the target was not characterized by a more-expressed P3 response, but by an occipital negativity. The current data confirm that the neural signatures of target awareness depend on the experimental setup used: In case of the DIB, the cross-modal setting might lead to a reduction of attentional resources in the visual domain.

Are auditory cues special? Evidence from cross-modal distractor-induced blindness

A target that shares features with preceding distractor stimuli is less likely to be detected due to a distractor-driven activation of a negative attentional set. This transient impairment in perceiving the target (distractor-induced blindness/deafness) can be found within vision and audition. Recently, the phenomenon was observed in a cross-modal setting involving an auditory target and additional task-relevant visual information (cross-modal distractor-induced deafness). In the current study, consisting of three behavioral experiments, a visual target, indicated by an auditory cue, had to be detected despite the presence of visual distractors. Multiple distractors consistently led to reduced target detection if cue and target appeared in close temporal proximity, confirming cross-modal distractor-induced blindness. However, the effect on target detection was reduced compared to the effect of cross-modal distractor-induced deafness previously observed for reversed modalities. The physical features defining cue and target could not account for the diminished distractor effect in the current cross-modal task. Instead, this finding may be attributed to the auditory cue acting as an especially efficient release signal of the distractor-induced inhibition. Additionally, a multisensory enhancement of visual target detection by the concurrent auditory signal might have contributed to the reduced distractor effect.

The Effect of Transcranial Direct Current Stimulation on Error Rates in the Distractor-Induced Deafness Paradigm.

To further understand how consciousness emerges, certain paradigms inducing distractor-induced perceptual impairments are promising. Neuro-computational models explain the inhibition of conscious perception of targets with suppression of distractor information when the target and distractor share the same features. Because these gating mechanisms are controlled by the prefrontal cortex, transcranial direct current stimulation of this specific region is expected to alter distractor-induced effects depending on the presence and number of distractors. To this end, participants were asked to perform an auditory variant of the distractor-induced blindness paradigm under frontal transcranial direct current stimulation (tDCS). Results show the expected distractor-induced deafness effects in a reduction of target detection depending on the number of distractors. While tDCS had no significant effects on target detection per se, error rates due to missed cues are increased under stimulation. Thus, while our variant led to successful replication of behavioral deafness effects, the results under tDCS stimulation indicate that the chosen paradigm may have difficulty too low to respond to stimulation. That the error rates nevertheless led to a tDCS effect may be due to the divided attention between the visual cue and the auditory target.

ERP signatures of auditory awareness in cross-modal distractor-induced deafness

Previous research showed that dual-task processes such as the attentional blink are not always transferable from unimodal to cross-modal settings. This study investigated whether such a transfer can be stated for a distractor-induced impairment of target detection established in vision (distractor-induced blindness, DIB) and recently observed in the auditory modality (distractor-induced deafness, DID). A cross-modal DID effect was confirmed: The detection of an auditory target indicated by a visual cue was impaired if multiple auditory distractors preceded the target. Event-related potentials (ERPs) were used to identify psychophysiological correlates of target detection. A frontal negativity about 200 ms succeeded by a sustained, widespread negativity was associated with auditory target awareness. In contrast to unimodal findings, P3 amplitude was not enhanced for hits. The results support the notion that early frontal attentional processes are linked to auditory awareness, whereas the P3 does not seem to be a reliable indicator of target access.

Distractor-induced deafness: The effect of multiple auditory distractors on conscious target processing

Conscious access to a target stimulus embedded in a rapid serial visual presentation can be impaired by the preceding presentation of multiple task-irrelevant distractors. While this phenomenon – labeled distractor-induced blindness (DIB) – is established in vision, it is unknown whether a similar effect can be observed in the auditory modality. Considering the differences in the processing of visual and auditory stimuli, modality-specific effects in the inhibitory mechanisms triggered by distractors can be expected. First, we aimed to find evidence for a distractor-induced deafness (DID) for auditory targets in a behavioral experiment. The target was defined by a transient increase in amplitude in a continuous sinusoidal tone, which was to be detected if accompanied or preceded by a deviant tone (cue). Both events were embedded in separate streams in a binaural rapid serial auditory presentation. Distractors preceded the cue and shared the target's features. As previously observed for DIB, a failure to detect the auditory target critically relied on the presentation of multiple distractor episodes. This DID effect was followed up in a subsequent event-related brain potentials (ERP) study to identify the signature of target detection. In contrast to missed targets, hits were characterized by a larger frontal negativity and by a more pronounced centro-parietal P3b wave. Whereas the latter process was also observed in the visual domain, indicating a post-perceptual updating process, the frontal negativity was exclusively observed for auditory DID. This modality-specific process might signal that early attentional control processes support conscious access to relevant auditory events.

Differential activation of a central inhibition system by motion and colour distractors

ABSTRACTThe selection of relevant stimuli is partially achieved through inhibition of irrelevant distractors. Using the distractor induced blindness (DIB) paradigm, we investigated whether these inhibitory processes depend on the feature dimension that is used to define distractors. Following a pilot study that found motion and colour targets to be comparably salient, we analysed distractor effects of those two feature dimensions. In both feature dimensions, an inhibition effect depended on the number of distractors. Colour, however, was more sensitive to distractor episodes as compared to motion: The level of inhibition was more pronounced, and its activation required less distractors. The results of a control experiment provided further evidence that, in fact, the feature dimension -instead of design differences between tasks- is responsible for this observation. The dimension-sensitive bias in the activation of a central inhibition system may be attributed to a differential processing of visual signals, depending on their behavioural relevance.

Adaptability and specificity of inhibition processes in distractor-induced blindness.

In a rapid serial visual presentation task, inhibition processes cumulatively impair processing of a target possessing distractor properties. This phenomenon-known as distractor-induced blindness-has thus far only been elicited using dynamic visual features, such as motion and orientation changes. In three ERP experiments, we used a visual object feature-color-to test for the adaptability and specificity of the effect. In Experiment I, participants responded to a color change (target) in the periphery whose onset was signaled by a central cue. Presentation of irrelevant color changes prior to the cue (distractors) led to reduced target detection, accompanied by a frontal ERP negativity that increased with increasing number of distractors, similar to the effects previously found for dynamic targets. This suggests that distractor-induced blindness is adaptable to color features. In Experiment II, the target consisted of coherent motion contrasting the color distractors. Correlates of distractor-induced blindness were found neither in the behavioral nor in the ERP data, indicating a feature specificity of the process. Experiment III confirmed the strict distinction between congruent and incongruent distractors: A single color distractor was embedded in a stream of motion distractors with the target consisting of a coherent motion. While behavioral performance was affected by the distractors, the color distractor did not elicit a frontal negativity. The experiments show that distractor-induced blindness is also triggered by visual stimuli predominantly processed in the ventral stream. The strict specificity of the central inhibition process also applies to these stimulus features.

Distractor-Induced Blindness: A Special Case of Contingent Attentional Capture?

The detection of a salient visual target embedded in a rapid serial visual presentation (RSVP) can be severely affected if target-like distractors are presented previously. This phenomenon, known as distractor-induced blindness (DIB), shares the prerequisites of contingent attentional capture (Folk, Remington, & Johnston, 1992). In both, target processing is transiently impaired by the presentation of distractors defined by similar features. In the present study, we investigated whether the speeded response to a target in the DIB paradigm can be described in terms of a contingent attentional capture process. In the first experiments, multiple distractors were embedded in the RSVP stream. Distractors either shared the target’s visual features (Experiment 1A) or differed from them (Experiment 1B). Congruent with hypotheses drawn from contingent attentional capture theory, response times (RTs) were exclusively impaired in conditions with target-like distractors. However, RTs were not impaired if only one single target-like distractor was presented (Experiment 2). If attentional capture directly contributed to DIB, the single distractor should be sufficient to impair target processing. In conclusion, DIB is not due to contingent attentional capture, but may rely on a central suppression process triggered by multiple distractors.

Open and closed cortico-subcortical loops: A neuro-computational account of access to consciousness in the distractor-induced blindness paradigm.

How the brain decides which information to process 'consciously' has been debated over for decades without a simple explanation at hand. While most experiments manipulate the perceptual energy of presented stimuli, the distractor-induced blindness task is a prototypical paradigm to investigate gating of information into consciousness without or with only minor visual manipulation. In this paradigm, subjects are asked to report intervals of coherent dot motion in a rapid serial visual presentation (RSVP) stream, whenever these are preceded by a particular color stimulus in a different RSVP stream. If distractors (i.e., intervals of coherent dot motion prior to the color stimulus) are shown, subjects' abilities to perceive and report intervals of target dot motion decrease, particularly with short delays between intervals of target color and target motion. We propose a biologically plausible neuro-computational model of how the brain controls access to consciousness to explain how distractor-induced blindness originates from information processing in the cortex and basal ganglia. The model suggests that conscious perception requires reverberation of activity in cortico-subcortical loops and that basal-ganglia pathways can either allow or inhibit this reverberation. In the distractor-induced blindness paradigm, inadequate distractor-induced response tendencies are suppressed by the inhibitory 'hyperdirect' pathway of the basal ganglia. If a target follows such a distractor closely, temporal aftereffects of distractor suppression prevent target identification. The model reproduces experimental data on how delays between target color and target motion affect the probability of target detection.

The state of a central inhibition system predicts access to visual targets: An ERP study on distractor-induced blindness (DIB).

Distractor-induced blindness (DIB) is elicited in a temporal selection task based on rapid serial visual presentation: Following the onset of a central cue (color change of fixation), a target in a global stream has to be detected (orientation change of tilted bars). Distractors are occasional target-like events presented prior to the onset of the cue. Depending on the number of distractor episodes, a frontal ERP negativity (FN) is evoked, and the detection rate of the forthcoming target is reduced. Here, we provide a concise review of the DIBs' functional characteristics, and examine the relationship between FN activation on target processing and detectability. To this end, ERP responses collected in a set of participants (n=14) were analysed separately with respect to detection performance (hits vs. misses). A gradual increase in the amplitude of the FN with increasing number of distractor events was only observed for forthcoming misses, but not for hits. The FN activation can be linked to a target-related ERP component: The amplitude of a late centro-parietal positivity (LPC) was significantly diminished for misses. In sum, the data support the notion that the DIB reflects the controlled activation of a central inhibition system. Depending on its state of activation, conscious access to stimuli defined by distinctive visual features is restricted.

Closing the Gates to Consciousness: Distractors Activate a Central Inhibition Process

The paradigm of distractor-induced blindness has previously been used to track the transition from unconscious to conscious visual processing. In a variation of this paradigm used in this study, participants (n = 13) had to detect an orientation change of tilted bars (target) embedded in a dynamic random pattern; the onset of the target was signaled by the presentation of a color cue. Occasional orientation changes preceding the cue served as distractors and severely impaired the target's detection. ERPs showed that a frontal negativity was cumulatively activated by the distractors, and early sensory components were not affected. In a control condition, the target was defined by a coherent motion of the bars. Orientation changes preceding the motion target did not affect its detection, and the frontal suppression process was not observed. However, we obtained a significant reduction of the sensory components. The data support the notion that distractors that share the target's features trigger a cumulative inhibition process preventing the conscious representation of the inhibited features. Explorative source modeling suggests that this process originates in the pFC. A top-down modulation of sensory processing could not be observed.

Distractor-induced blindness for orientation changes and coherent motion

The conscious perception of simple visual stimuli can be modulated by the presence of distractors. In the motion blindness paradigm, the detection of coherent motion is impaired when task-irrelevant motion distractors are presented prior to the target. Aim of this study was to examine the feature specificity of the distractor effect. For this reason, targets were either defined by motion coherence (“motion blindness”) or orientation changes (“orientation blindness”). In a series of three experiments we show that distractors have to share the feature characteristics of the target in order to reduce its detectability. However, independent inhibition sets for visual features can be activated if the targets’ characteristics are ambiguous.