Failure of temporal selectivity: Electrophysiological evidence for (mis)selection of distractors during the attentional blink

Transient Attention Gates Access Consciousness: Coupling N2pc and P3 Latencies Using Dynamic Time Warping

The N2pc and P3 event-related potentials (ERPs), used to index selective attention and access to working memory and conscious awareness, respectively, have been important tools in cognitive sciences. Although it is likely that these two components and the underlying cognitive processes are temporally and functionally linked, such links have not yet been convincingly demonstrated. Adopting a novel methodological approach based on dynamic time warping (DTW), we provide evidence that the N2pc and P3 ERP components are temporally linked. We analyzed data from an experiment where 23 participants (16 women) monitored bilateral rapid serial streams of letters and digits in order to report a target digit indicated by a shape cue, separately for trials with correct responses and trials where a temporally proximal distractor was reported instead (distractor intrusion). DTW analyses revealed that N2pc and P3 latencies were correlated in time, both when the target or a distractor was reported. Notably, this link was weaker on distractor intrusion trials. This N2pc-P3 association is discussed with respect to the relationship between attention and access consciousness. Our results demonstrate that our novel method provides a valuable approach for assessing temporal links between two cognitive processes and their underlying modulating factors. This method allows to establish links and their modulator for any two time-series across all domains of the field (general-purpose MATLAB functions and a Python module are provided alongside this paper).

Neural correlates of consciousness in an attentional blink paradigm with uncertain target relevance

Several event-related potentials (ERPs) have been proposed as neural correlates of consciousness (NCC), most prominently the early visual awareness negativity (VAN) and the late P3b component. Highly influential support for the P3b comes from studies utilizing the attentional blink (AB), where conscious perception of a first visual target (T1) impairs reporting a second target (T2) presented shortly afterwards. Recent no-report studies using other paradigms suggest that the P3b component may reflect post-perceptual processes associated with decision-making rather than awareness. However, no-report studies are limited in their awareness assessment, and their conclusions have not been tested in an AB paradigm. The present study (N = 38) addressed these issues using a novel AB paradigm, which reduced decision-making processes by omitting a discrimination task on T2 stimuli and rendering their relevance uncertain. Nevertheless, awareness was assessed trial by trial. Comparing ERPs in response to seen versus unseen T2 stimuli revealed a VAN but no enhanced P3b regardless of whether they were marked as distinct from distractor stimuli or not. Our results corroborate the VAN and challenge the P3b as NCC despite rigorous trial-by-trial assessment of conscious perception. Thus, they support the idea that awareness emerges during early sensory processing.

Alteration of early attentional processing after analogue trauma exposure: evidence from event-related potentials

The present study aimed to determine whether exposure to an analogue traumatic event affects attentional processing of emotional information. Two groups of non-clinical participants matched on anxiety level, depression symptoms and stressful life events viewed either a trauma or a neutral film. They then performed an emotional Stroop task during which both continuous electroencephalographic activity was recorded and intrusive memories were measured. Results revealed that the valence effect (measured by the difference between emotional and neutral conditions) for the P1 amplitude was significantly greater in participants who viewed the trauma film than in participants who viewed the neutral film. This interaction was specific to words semantically related to the analogue trauma event and did not extend to all negative words. Further analyses revealed a relationship between intrusions frequency, P1 amplitude and emotional Stroop interference, indicating a link between attention and intrusive memories. Our findings suggest that exposure to potentially traumatic events has an important impact on neurocognitive function, even in the absence of psychopathology, and that this impact occurs at an early, possibly automatic stage of processing.

What processes are disrupted during the attentional blink? An integrative review of event-related potential research

Reporting the second of two targets is impaired when these appear in close succession, a phenomenon known as the attentional blink (AB). Despite decades of research, what factors limit our ability to process multiple sequentially presented events remains unclear. Specifically, two central issues remain open: does failure to report the second target (T2) reflect a structural limitation in working memory (WM) encoding or a disruption to attentional processes? And is perceptual processing of the stimulus that we fail to report impaired, or only processes that occur after this stimulus is identified? We address these questions by reviewing event-related potential (ERP) studies of the AB, after providing a brief overview of the theoretical landscape relevant to these debates and clarifying key concepts essential for interpreting ERP studies. We show that failure to report the second target is most often associated with disrupted attentional engagement (associated with a smaller and delayed N2pc component). This disruption occurs after early processing of T2 (associated with an intact P1 component), weakens its semantic processing (typically associated with a smaller N400 component), and prevents its encoding into WM (associated with absent P3b). However, failure to encode T2 in WM can occur despite intact attentional engagement and semantic processing. We conclude that the AB phenomenon, which reflects our limited ability to process sequential events, emerges from the disruption of both attentional engagement and WM encoding.

Dual task interference on early perceptual processing

When two tasks, Task 1 and Task 2, are conducted in close temporal proximity and a separate speeded response is required for each target (T1 and T2), T2 report performance decreases as a function of its temporal proximity to T1. This so-called psychological refractory period (PRP) effect on T2 processing is largely assumed to reflect interference from T1 response selection on T2 response selection. However, interference on early perceptual processing of T2 has been observed in a modified paradigm, which required changes in visual-spatial attention, sensory modality, task modality, and response modality across targets. The goal of the present study was to investigate the possibility of early perceptual interference by systematically and iteratively removing each of these possible non perceptual confounds, in a series of four experiments. To assess T2 visual memory consolidation success, T2 was presented for a varying duration and immediately masked. T2 report accuracy, which was taken as a measure of perceptual-encoding or consolidation-success, decreased across all experimental control conditions as T1-T2 onset proximity increased. We argue that our results, in light of previous studies, show that central processing of a first target, responsible for the classical PRP effect, also interferes with early perceptual processing of a second target. We end with a discussion of broader implications for psychological refractory period and attentional blink effects.

Access to consciousness of briefly presented visual events is modulated by transcranial direct current stimulation of left dorsolateral prefrontal cortex

Adaptive behaviour requires the ability to process goal-relevant events at the expense of irrelevant ones. However, perception of a relevant visual event can transiently preclude access to consciousness of subsequent events — a phenomenon called attentional blink (AB). Here we investigated involvement of the left dorsolateral prefrontal cortex (DLPFC) in conscious access, by using transcranial direct current stimulation (tDCS) to potentiate or reduce neural excitability in the context of an AB task. In a sham-controlled experimental design, we applied between groups anodal or cathodal tDCS over the left DLPFC, and examined whether this stimulation modulated the proportion of stimuli that were consciously reported during the AB period. We found that tDCS over the left DLPFC affected the proportion of consciously perceived target stimuli. Moreover, anodal and cathodal tDCS had opposing effects, and exhibited different temporal patterns. Anodal stimulation attenuated the AB, enhancing conscious report earlier in the AB period. Cathodal stimulation accentuated the AB, reducing conscious report later in the AB period. These findings support the notion that the DLPFC plays a role in facilitating information transition from the unconscious to the conscious stage of processing.

Perceptual Processing is Not Spared During the Attentional Blink

Identification of the second of two targets is impaired when these appear within 500 ms of each other. This phenomenon, known as the attentional blink (AB) is thought to reflect disrupted post-perceptual processing. Yet, decisive empirical support for this claim is lacking. We measured the depth of the AB, while manipulating the second target’s reporting feature. We reasoned that if perceptual processing is unaffected by the blink, all the features of the blinked target should have equal access to working memory. In contrast with this prediction, we found identity and semantic-category reports to be more severely impaired by the blink than color reports, although baseline performance was similar in the two report conditions. These findings suggest that high-level features are more poorly represented in working memory than low-level features during the blink. We conclude that the attentional blink disrupts perceptual processing. Implications for contemporary models of the attentional blink are discussed.

Sexual Abuse Exposure Alters Early Processing of Emotional Words: Evidence from Event-Related Potentials

This study aimed to compare the time course of emotional information processing between trauma-exposed and control participants, using electrophysiological measures. We conceived an emotional Stroop task with two types of words: trauma-related emotional words and neutral words. We assessed the evoked cerebral responses of sexual abuse victims without post-traumatic stress disorder (PTSD) and no abuse participants. We focused particularly on an early wave (C1/P1), the N2pc, and the P3b. Our main result indicated an early effect (55–165 ms) of emotionality, which varied between non-exposed participants and sexual abuse victims. This suggests that potentially traumatic experiences modulate early processing of emotional information. Our findings showing neurobiological alterations in sexual abuse victims (without PTSD) suggest that exposure to highly emotional events has an important impact on neurocognitive function even in the absence of psychopathology.

Manipulating the focus of attention in working memory: Evidence for a protection of multiple items against perceptual interference

Visual working memory representations can be shielded from interference by selective attentional focusing using retroactive cues (retro-cues). However, it is not clear how many representations can be effectively cued and which neural mechanisms provide the protection from distractors. To address these questions, we manipulated the number of attended items by means of a retro-cue (one, two, or three items) and presented a distractor display during the retention of information in working memory. Analyses of the raw error and a mixture model revealed that a general performance benefit was only present when one item was retro-cued. Nevertheless, a protection of the item representations against subsequent interference occurred also after a two-item cue. ERPs revealed a modulation of the posterior negative slow wave following the retro-cues, reflecting the applied working memory resources dependent on the number of attended representations. Further, the distractor information was encoded into working memory only when the number of attended items was not changed by the retro-cues (neutral and three-item conditions), reflected by a P3b following the distractor display. These results suggest that more than one item can be effectively protected from perceptual interference. We propose that the protective effect of selective attention within working memory is based on both a reduction of the number of focused representations and the attentional refreshing of item context and features.

Time to see the bigger picture: Individual differences in the attentional blink

If two to-be-identified targets are presented in close temporal succession, identification for the second target is typically impaired. This attentional blink (AB) phenomenon has long been considered as a robust, universal cognitive limitation. However, more recent studies have demonstrated that AB task performance greatly differs between individuals, with some individuals even showing no AB in certain paradigms. Several studies have focused on these individual differences in an attempt to reveal the mechanism underlying the AB, but an overview of this approach is currently missing. Here, by reviewing studies regarding individual differences in AB task performance, we investigate how individual differences have contributed to our understanding of the AB. We show that the individual differences AB literature provides reliable indications that the AB is a multifaceted phenomenon that presumably arises from a combination of factors; individuals with higher levels of executive working memory (WM) functioning and broad attentional focus perform better in the AB paradigm than individuals with lower executive functioning of WM and narrow attentional focus. As it turns out, seeing the bigger picture certainly seems helpful for AB task performance.