Distractor suppression when attention fails: behavioral evidence for a flexible selective attention mechanism

An online browser-based attentional blink replication using visual objects

The complex relationship between attention and visual perception can be exemplified and investigated through the Attentional Blink. The attentional blink is characterised by impaired attention to the second of two target stimuli, when both occur within 200 - 500ms. The attentional blink has been well studied in experimental lab settings. However, despite the rise of online methods for behavioural research, their suitability for studying the attentional blink has not been fully addressed yet, the main concern being the lack of control and timing variability for stimulus presentation. Here, we investigated the suitability of online testing for studying the attentional blink with visual objects. Our results show a clear attentional blink effect between 200 to 400ms following the distractor including a Lag 1 sparing effect in line with previous research despite significant inter-subject and timing variability. This work demonstrates the suitability of online methods for studying the attentional blink with visual objects, opening new avenues to explore its underlying processes.

Disruptions of Sustained Spatial Attention Can Be Resistant to the Distractor's Prior Reward Associations

Attention can be involuntarily biased toward reward-associated distractors (value-driven attentional capture, VDAC). Yet past work has primarily demonstrated this distraction phenomenon during a particular set of circumstances: transient attentional orienting to potentially relevant stimuli occurring in our visual environment. Consequently, it is not well-understood if reward-based attentional capture can occur under other circumstances, such as during sustained visuospatial attention. Using EEG, we investigated whether associating transient distractors with reward value would increase their distractibility and lead to greater decrements in concurrent sustained spatial attention directed elsewhere. Human participants learned to associate three differently colored, laterally presented squares with rewards of varying magnitude (zero, small, and large). These colored squares were then periodically reintroduced as distractors at the same lateral locations during a demanding sustained-attention rapid-serial-visual-presentation (RSVP) task at the midline. Behavioral and neural evidence indicated that participants had successfully learned and maintained the reward associations to the distractors. During the RSVP task, consistent with prior work, we found that the distractors generated dips in the instantaneous amplitude of the steady-state visual evoked potentials (SSVEPs) elicited by the midline RSVP stimuli, indicating that the distractors were indeed transiently disrupting sustained spatial attention. Contrary to our hypotheses, however, the magnitude of this dip did not differ by the magnitude of the distractor’s reward associations. These results indicate that while sustained spatial attention can be impaired by the introduction of distractors at another location, the main distraction process is resistant to the distractors’ reward associations, thus providing evidence of an important boundary condition to value-driven attentional capture.

No Effect of Transcranial Direct Current Stimulation over Left Dorsolateral Prefrontal Cortex on Temporal Attention

Selection mechanisms that dynamically gate only relevant perceptual information for further processing and sustained representation in working memory are critical for goal-directed behavior. We examined whether this gating process can be modulated by transcranial direct current stimulation (tDCS) over left dorsolateral prefrontal cortex (lDLPFC)-a region known to play a key role in working memory and conscious access. Specifically, we examined the effects of tDCS on the magnitude of the "attentional blink" (AB), a deficit in identifying the second of two targets presented in rapid succession. Thirty-four participants performed an AB task before (baseline), during and after 20 min of 1-mA anodal and cathodal tDCS in two separate sessions. On the basis of previous reports linking individual differences in AB magnitude to individual differences in DLPFC activity and on the basis of suggestions that effects of tDCS depend on baseline brain activity levels, we hypothesized that anodal tDCS over lDLPFC would modulate the magnitude of the AB as a function of individual baseline AB magnitude. Behavioral results did not provide support for this hypothesis. At the group level, we also did not observe any significant effects of tDCS, and a Bayesian analysis revealed strong evidence that tDCS to lDLPFC did not affect AB performance. Together, these findings do not support the idea that there is an optimal level of prefrontal cortical excitability for cognitive function. More generally, they add to a growing body of work that challenges the idea that the effects of tDCS can be predicted from baseline levels of behavior.

The perceptual wink model of non-switching attentional blink tasks

The attentional blink (AB) is a temporary deficit for a second target (T2) when that target appears after a first target (T1). Although sophisticated models have been developed to explain the substantial AB literature in isolation, the current study considers how the AB relates to perceptual dynamics more broadly. We show that the time-course of the AB is closely related to the time course of the transition from positive to negative repetition priming effects in perceptual identification. Many AB tasks involve a switch between a T1 defined in one manner and a T2 defined in a different manner. Other AB tasks are non-switching, with all targets belonging to the same well-known category (e.g., letter targets versus number distractors) or sharing the same perceptual feature. We propose that these non-switching AB tasks reflect perceptual habituation for the target-defining attribute; thus, a 'perceptual wink', with perception of one attribute (target identity) undisturbed while perception of another (target detection) is impaired. On this account, the immediate benefit following T1 (lag-1 sparing) reflects positive repetition priming and the subsequent deficit (the blink) reflects negative repetition priming for the realization that a target occurred. In developing the perceptual wink model, we extended the nROUSE model of perceptual priming to explain the results of two new experiments combining the AB and identity repetitions. This establishes important connections between non-switching AB tasks and perceptual dynamics.

Summary statistics in the attentional blink

We used the attentional blink (AB) paradigm to investigate the processing stage at which extraction of summary statistics from visual stimuli ("ensemble coding") occurs. Experiment 1 examined whether ensemble coding requires attentional engagement with the items in the ensemble. Participants performed two sequential tasks on each trial: gender discrimination of a single face (T1) and estimating the average emotional expression of an ensemble of four faces (or of a single face, as a control condition) as T2. Ensemble coding was affected by the AB when the tasks were separated by a short temporal lag. In Experiment 2, the order of the tasks was reversed to test whether ensemble coding requires more working-memory resources, and therefore induces a larger AB, than estimating the expression of a single face. Each condition produced a similar magnitude AB in the subsequent gender-discrimination T2 task. Experiment 3 additionally investigated whether the previous results were due to participants adopting a subsampling strategy during the ensemble-coding task. Contrary to this explanation, we found different patterns of performance in the ensemble-coding condition and a condition in which participants were instructed to focus on only a single face within an ensemble. Taken together, these findings suggest that ensemble coding emerges automatically as a result of the deployment of attentional resources across the ensemble of stimuli, prior to information being consolidated in working memory.

Transient Distraction and Attentional Control during a Sustained Selective Attention Task

Distracting stimuli in the environment can pull our attention away from our goal-directed tasks. fMRI studies have implicated regions in right frontal cortex as being particularly important for processing distractors [e.g., de Fockert, J. W., & Theeuwes, J. Role of frontal cortex in attentional capture by singleton distractors. Brain and Cognition, 80, 367-373, 2012; Demeter, E., Hernandez-Garcia, L., Sarter, M., & Lustig, C. Challenges to attention: A continuous arterial spin labeling (ASL) study of the effects of distraction on sustained attention. Neuroimage, 54, 1518-1529, 2011]. Less is known, however, about the timing and sequence of how right frontal or other brain regions respond selectively to distractors and how distractors impinge upon the cascade of processes related to detecting and processing behaviorally relevant target stimuli. Here we used EEG and ERPs to investigate the neural consequences of a perceptually salient but task-irrelevant distractor on the detection of rare target stimuli embedded in a rapid, serial visual presentation (RSVP) stream. We found that distractors that occur during the presentation of a target interfere behaviorally with detection of those targets, reflected by reduced detection rates, and that these missed targets show a reduced amplitude of the long-latency, detection-related P3 component. We also found that distractors elicited a right-lateralized frontal negativity beginning at 100 msec, whose amplitude negatively correlated across participants with their distraction-related behavioral impairment. Finally, we also quantified the instantaneous amplitude of the steady-state visual evoked potentials elicited by the RSVP stream and found that the occurrence of a distractor resulted in a transient amplitude decrement of the steady-state visual evoked potential, presumably reflecting the pull of attention away from the RSVP stream when distracting stimuli occur in the environment.

Effects of Transcranial Direct Current Stimulation over Left Dorsolateral pFC on the Attentional Blink Depend on Individual Baseline Performance

Selection mechanisms that dynamically gate only relevant perceptual information for further processing and sustained representation in working memory are critical for goal-directed behavior. We examined whether this gating process can be modulated by anodal transcranial direct current stimulation (tDCS) over left dorsolateral pFC (DLPFC)—a region known to play a key role in working memory and conscious access. Specifically, we examined the effects of tDCS on the magnitude of the so-called “attentional blink” (AB), a deficit in identifying the second of two targets presented in rapid succession. Thirty-four participants performed a standard AB task before (baseline), during, and after 20 min of 1-mA anodal and cathodal tDCS in two separate sessions. On the basis of previous reports linking individual differences in AB magnitude to individual differences in DLPFC activity and on suggestions that effects of tDCS depend on baseline brain activity levels, we hypothesized that anodal tDCS over left DLPFC would modulate the magnitude of the AB as a function of individual baseline AB magnitude. Indeed, individual differences analyses revealed that anodal tDCS decreased the AB in participants with a large baseline AB but increased the AB in participants with a small baseline AB. This effect was only observed during (but not after) stimulation, was not found for cathodal tDCS, and could not be explained by regression to the mean. Notably, the effects of tDCS were not apparent at the group level, highlighting the importance of taking individual variability in performance into account when evaluating the effectiveness of tDCS. These findings support the idea that left DLPFC plays a critical role in the AB and in conscious access more generally. They are also in line with the notion that there is an optimal level of prefrontal activity for cognitive function, with both too little and too much activity hurting performance.