Contralateral Delay Activity Amplitude Research Articles

Anticipatory processing increases attentional biases to disgust faces in socially anxious individuals: Evidence from the N2pc and CDA

Attentional biases to socially threatening facial expressions (anger, disgust) have been repeatedly observed in socially anxious individuals. These biases are thought to arise, in part, because anticipatory processing of social situations increases the salience of negative social cues. Additionally, self-focused attention on somatic symptoms of anxiety (e.g., heart rate) is thought to interfere with attentional bias. The goal of this study was to examine how anticipatory processing and self-focused attention affect attentional biases as reflected by reliable, temporally precise event-related potentials (ERPs), namely the N2pc and contralateral delay activity (CDA), which index selective attention and working memory maintenance, respectively. One-hundred forty undergraduate students at two collaborating universities completed a mentation task in which they were randomly assigned to engage in prompt-guided anticipatory processing or neutral distraction after being told that they would be evaluated during a social interaction with a researcher at the end of the study. Participants then completed a dot-probe task with disgust/neutral face pairs. To manipulate self-focused attention, the fixation cross was randomly rotated between (+) or (×), and participants were told that one of these indicated an increase in their heart rate. Probes appeared 800 ms after face stimulus offset so that the CDA could be measured. N2pc and CDA amplitude were larger in the anticipatory processing condition compared to distraction for socially anxious individuals, and this effect remained when controlling for depression. There was no effect involving self-focused attention. The results support anticipatory processing as an important process that affects attentional bias in socially anxious individuals.

Hearing fearful prosody impairs visual working memory maintenance

Interference by distractors has been associated multiple times with diminished visual and auditory working memory (WM) performance. Negative emotional distractors in particular lead to detrimental effects on WM. However, these associations have only been seen when distractors and items to maintain in WM are from the same sensory modality. In this study, we investigate cross-modal interference on WM. We invited 20 participants to complete a visual change-detection task, assessing visual WM (VWM), while hearing emotional (fearful) and neutral auditory distractors. Electrophysiological activity was recorded to measure contralateral delay activity (CDA) and auditory P2 event-related potentials (ERP), indexing WM maintenance and distractor salience respectively. At the behavioral level, fearful prosody didn't decrease significantly working memory accuracy, compared to neutral prosody. Regarding ERPs, fearful distractors evoked a greater P2 amplitude than neutral distractors. Correlations between the two ERP potentials indicated that P2 amplitude difference between the two types of prosody was associated with the difference in CDA amplitude for fearful and neutral trials. This association suggests that cognitive resources required to process fearful prosody detrimentally impact VWM maintenance. That result provides a piece of additional evidence that negative emotional stimuli produce greater interference than neutral stimuli and that the cognitive resources used to process stimuli from different modalities come from a common pool.

Decomposing neurophysiological underpinnings of age-related decline in visual working memory

Exploring the neural basis of age-related decline in working memory is vital in our aging society. Previous electroencephalographic studies suggested that the contralateral delay activity (CDA) may be insensitive to age-related decline in lateralized visual working memory (VWM) performance. Instead, recent evidence indicated that task-induced alpha power lateralization decreases in older age. However, the relationship between alpha power lateralization and age-related decline of VWM performance remains unknown, and recent studies have questioned the validity of these findings due to confounding factors of the aperiodic signal. Using a sample of 134 participants, we replicated the age-related decrease of alpha power lateralization after adjusting for the aperiodic signal. Critically, the link between task performance and alpha power lateralization was found only when correcting for aperiodic signal biases. Functionally, these findings suggest that age-related declines in VWM performance may be related to the decreased ability to prioritize relevant over irrelevant information. Conversely, CDA amplitudes were stable across age groups, suggesting a distinct neural mechanism possibly related to preserved VWM encoding or early maintenance.

The reactivation of task rules triggers the reactivation of task-relevant items

Working memory (WM) describes the temporary storage of task-relevant items and procedural rules to guide action. Despite its central importance for goal-directed behavior, the interplay between WM and long-term memory (LTM) remains poorly understood. Recent studies have shown that repeated use of the same task-relevant item in WM results in a hand-off of the storage of that item to LTM, and switching to a new item reactivates WM. To further elucidate the rules governing WM-LTM interactions, we here planned to probe whether a change in task rules, independent of a switch in task-relevant items, would also lead to WM reactivation of maintained items. To this end, we used scalp-recorded electroencephalogram (EEG) data, specifically the contralateral delay activity (CDA), to track WM item storage while manipulating repetitions and changes in task rules and task-relevant items across trials in a visual WM task. We tested two rival hypotheses: If changes in task rules result in a reactivation of the target item representation, then the CDA should increase when a task change is cued even when the same target has been repeated across trials. However, if the reactivation of a task-relevant item only depends on the mnemonic availability of the item itself instead of the task it is used for, then only the changes in task-relevant items should reactivate the representations. Accordingly, the CDA amplitude should decrease for repeated task-relevant items independently of a task change. We found a larger CDA on task-switch compared to task-repeat trials, suggesting that the reactivation of task rules triggers the reactivation of task-relevant items in WM. By demonstrating that WM reactivation of LTM is interdependent for task rules and task-relevant items, this study informs our understanding of visual WM and its interplay with LTM. Preregistered Stage 1 protocolhttps://osf.io/zp9e8 (date of in-principle acceptance: 19/12/2021).

Visual short-term memory-related EEG components in a virtual reality setup.

Virtual reality (VR) offers a powerful tool for investigating cognitive processes, as it allows researchers to gauge behaviors and mental states in complex, yet highly controlled, scenarios. The use of VR head-mounted displays in combination with physiological measures such as EEG presents new challenges and raises the question whether established findings also generalize to a VR setup. Here, we used a VR headset to assess the spatial constraints underlying two well-established EEG correlates of visual short-term memory: the amplitude of the contralateral delay activity (CDA) and the lateralization of induced alpha power during memory retention. We tested observers' visual memory in a change detection task with bilateral stimulus arrays of either two or four items while varying the horizontal eccentricity of the memory arrays (4, 9, or 14 degrees of visual angle). The CDA amplitude differed between high and low memory load at the two smaller eccentricities, but not at the largest eccentricity. Neither memory load nor eccentricity significantly influenced the observed alpha lateralization. We further fitted time-resolved spatial filters to decode memory load from the event-related potential as well as from its time-frequency decomposition. Classification performance during the retention interval was above-chance level for both approaches and did not vary significantly across eccentricities. We conclude that commercial VR hardware can be utilized to study the CDA and lateralized alpha power, and we provide caveats for future studies targeting these EEG markers of visual memory in a VR setup.

Contralateral delay activity, but not alpha lateralization, indexes prioritization of information for working memory storage

Working memory is inherently limited, which makes it important to select and maintain only task-relevant information and to protect it from distraction. Previous research has suggested the contralateral delay activity (CDA) and lateralized alpha oscillations as neural candidates for such a prioritization process. While most of this work focused on distraction during encoding, we examined the effect of external distraction presented during memory maintenance. Participants memorized the orientations of three lateralized objects. After an initial distraction-free maintenance interval, distractors appeared in the same location as the targets or in the opposite hemifield. This distraction was followed by another distraction-free interval. Our results show that CDA amplitudes were stronger in the interval before compared with the interval after the distraction (i.e., CDA amplitudes were stronger in response to targets compared with distractors). This amplitude reduction in response to distractors was more pronounced in participants with higher memory accuracy, indicating prioritization and maintenance of relevant over irrelevant information. In contrast, alpha lateralization did not change from the interval before distraction compared with the interval after distraction, and we found no correlation between alpha lateralization and memory accuracy. These results suggest that alpha lateralization plays no direct role in either selective maintenance of task-relevant information or inhibition of distractors. Instead, alpha lateralization reflects the current allocation of spatial attention to the most salient information regardless of task-relevance. In contrast, CDA indicates flexible allocation of working memory resources depending on task-relevance.

One turn at a time: Behavioral and ERP evidence for two types of rotations in the classical mental rotation task.

We perform mental rotations in many everyday situations, such as reading a map or following furniture assembling instructions. In a classical mental rotation task, participants are asked to judge whether a rotated stimulus is presented in its mirrored form or its canonical form. Previous results have indicated a degree effect: RT is longer as the angle of rotation increases, and this effect is traditionally explained by arguing that this judgment requires rotating the stimulus back to its upright form. Importantly, in half of the trials, the stimuli are rotated on both the page plane and mirror plane. Namely, we argue that in previous research the task actually involved two different rotation processes. To provide a clear dissociation between these two rotations, we collected EEG data and used the Contralateral Delay Activity (CDA) as an indicator of visual working memory (VWM) load. The results of Experiment 1 suggested different VWM involvement according to the degrees rotations when the item was not mirrored, such that the CDA amplitude generally increased as the degree of rotation was higher. Mirrored trials were all at ceiling in terms of CDA, regardless of their rotation degree. Experiment 2 showed increased CDA amplitude uniquely related to the flip rotation. Thus, we provided ERP evidence that the canonical mental rotation task involves two types of rotations that can be dissociated based on the load they imposed on VWM.

The effects of acute high-intensity interval exercise on the temporal dynamics of working memory and contralateral delay activity.

The present investigation examined the acute effects of high-intensity interval exercise (HIIE) on temporal changes in behavioral and neuroelectrical indices of working memory. Young adults (n=22) performed a visual working memory change detection task of equiprobable 2- to 5-dot set sizes while contralateral delay activity (CDA) and N2pc ERP components were assessed at three consecutive time periods (40-min, 54-min, and 68-min) following three separate counterbalanced 9-min sessions of seated rest, HIIE-aerobic (treadmill intervals of moderate- and high-intensity run/walk periods) and HIIE-aerobic/resistance (intervals of rest and body-weight calisthenics). Behavior results revealed greater 4-dot accuracy for HIIE-aerobic/resistance compared to seated rest only at 40-min, maintenance of 5-dot accuracy across time for HIIE-aerobic compared to HIIE-aerobic/resistance and seated rest, and greater temporal stability in overall accuracy performance (i.e., inter-class correlation between temporally adjacent assessments) for both HIIE conditions compared to seated rest. CDA and N2pc results revealed no change in amplitude across time and between HIIE-aerobic, HIIE-aerobic/resistance, and seated rest. However, greater temporal stability in CDA amplitude was observed for HIIE-aerobic compared to seated rest. These findings suggest that short bouts of HIIE may serve as an effective modality for improvements and temporal stabilization in behavior with some evidence for stabilization of neuroelectrical indices of working memory capacity. Together, these data broadly suggest that short acute bouts of exercise may facilitate improvements in underlying mental operations responsible for temporal stability in cognitive and neurocognitive function.

Effect of test anxiety on visual working memory capacity using evidence from event-related potentials.

This study examined the effects of test anxiety on working memory capacity. Studies have demonstrated that individuals with trait social anxiety disorder exhibit increased visual working memory capacity and that those with trait anxiety exhibit decreased working memory capacity. Test anxiety may also induce unique effects on individuals' working memory capacity, and we thus employed the change detection task to explore such effects. Participants were divided into high- and low-test anxiety groups. We used K score and contralateral delay activity (CDA) amplitude to measure working memory capacity, focusing on processing effectiveness and efficiency. The study results revealed that deficits in the working memory capacity of individuals in the high test anxiety group manifested in the CDA amplitude rather than in the K score. The CDA amplitude of the high test anxiety group did not increase after load 3, and that of the low test anxiety group did not increase after load 4. No difference was observed in the K scores of the two groups. The study concluded that test anxiety impairs processing efficiency but not processing effectiveness.

Psychophysiological, but Not Behavioral, Indicator of Working Memory Capacity Predicts Video Game Proficiency.

Visual working memory (VWM) is the ability to actively maintain visual information over short periods of time and is strongly related to global fluid intelligence and overall cognitive ability. In our study, we used two indices of visual working memory capacity: the behavioral estimate of capacity (K) and contralateral delay activity (CDA) in order to check whether training in a Real-Time Strategy (RTS) video game StarCraft II can influence the VWM capacity measured by the change detection task. We also asked a question whether individual differences in behavioral and psychophysiological indices of VWM can predict the effectiveness of video game training. Sixty-two participants (non-players) were recruited to the experiment. Participants were randomly assigned to either experimental (Variable environment), active control (Fixed environment), and passive control groups. Experimental and active control groups differed in the type of training received. Training consisted of 30 h of playing the StarCraft II game. Participants took part in two EEG sessions (pre- and post-training) during which they performed the VWM task. Our results showed that working memory capacity (K calculated according to Pashler’s formula) increases after training in both experimental groups, but not in a control group. We have also found a correlation between average visual working memory capacity (calculated as K) and mean CDA amplitude no matter which group we are looking at. And, last but not least, we have found that we can predict the amount of improvement in the RTS video game by looking at the psychophysiological indices (CDA amplitude) recorded at baseline (before training), but only in the experimental group. We think that the strength of the psychophysiological indicator of VWM capacity might be a marker of the future success in video game acquisition.

Estimating the statistical power to detect set-size effects in contralateral delay activity.

The contralateral delay activity (CDA) is an event-related potential component commonly used to examine the online processes of visual working memory. Here, we provide a robust analysis of the statistical power that is needed to achieve reliable and reproducible results with the CDA. Using two very large EEG datasets that examined the contrast between CDA amplitude with set sizes 2 and 6 items and set sizes 2 and 4 items, we present a subsampling analysis that estimates the statistical power achieved with varying numbers of subjects and trials based on the proportion of significant tests in 10,000 iterations. We also generated simulated data using Bayesian multilevel modeling to estimate power beyond the bounds of the original datasets. The number of trials and subjects required depends critically on the effect size. Detecting the presence of the CDA-a reliable difference between contralateral and ipsilateral electrodes during the memory period-required only 30-50 clean trials with a sample of 25 subjects to achieve approximately 80% statistical power. However, for detecting a difference in CDA amplitude between two set sizes, a substantially larger number of trials and subjects were required; approximately 400 clean trials with 25 subjects to achieve 80% power. Thus, to achieve robust tests of how CDA activity differs across conditions, it is essential to be mindful of the estimated effect size. We recommend researchers designing experiments to detect set-size differences in the CDA collect substantially more trials per subject.

Personal relative deprivation impairs ability to filter out threat-related distractors from visual working memory

The literature has indicated that personal relative deprivation (PRD) results in anxiety disorders. Given that some cognitive models propose that attention bias toward a threat causes and maintains anxiety, relatively deprived individuals may have difficulty gating threat from working memory. To test this hypothesis, this study investigated the influence of PRD on the filtering ability of happy, angry, and neutral facial distractors from visual working memory using electroencephalography (EEG). Participants were randomly assigned to a PRD (n = 24) or a non-PRD group (n = 24). Filtering ability was reflected by comparing the contralateral delay activity (CDA) amplitude for one-target, one-target-one-distractor, and two-targets conditions. The CDA was measured as the difference in mean amplitudes between activity in the hemispheres contralateral and ipsilateral to the to-be-remembered information. Results indicated that individuals in the PRD group showed a reduced ability to filter out neutral and angry facial distractors, as reflected by similar CDA amplitudes for one-target-one-distractor and two-targets conditions for both angry and neutral distractors in the PRD group. However, PRD did not impair the ability to filter out happy facial distractors, as reflected by similar CDA amplitudes for one-target-one-distractor and one-target conditions for happy distractors in the PRD group. As neutral faces might then be taken as potentially threatening information by relatively deprived individuals, these results support the hypothesis that relatively deprived individuals might have difficulty filtering out threat-related information.

What is the role of working memory in hybrid search?: Evidence from the Contralateral Delay Activity

In Hybrid Search, observers search for any member of a set of targets held in memory. Current hybrid search models propose working memory (WM) serves to pass representations of attended items one at a time from early visual processes into long-term memory (LTM) for comparison to target representations (Drew, et al., 2015). Here, we sought to better understand the role of WM in hybrid search using an ERP component associated with WM load, the Contralateral Delay Activity (CDA). Participants (N=20) memorized setsizes (MSS) of 2 or 16 categorical targets (dogs, cats, tables, or dressers), counterbalanced across participants. Next, they passed a recognition memory test twice with >=80% accuracy. Then, for 700 trials (per MSS), participants were cued to attend to one lateralized search item and indicate if a target was present. The cued object was either a target (e.g., target cat), a non-target from the target category (e.g., non-target cat), a non-target from a similar category (e.g., dog), or a non-target from a dissimilar category (e.g., table). ERP waveforms were time-locked to search onset. Overall, CDA amplitude was larger for objects from the target category, which provides support for the idea that processing is terminated for irrelevant objects following initial object identification (Cunningham & Wolfe, 2014). For objects within the target category, CDA amplitude increased with MSS, suggesting LTM load-dependent WM involvement in hybrid search. Furthermore, N2pc amplitude increased as the non-targets became more similar to the object category, but only for MSS16. This suggests more non-targets with similar features were selected for further processing in memory at larger MSS. Together, these findings demonstrate WM plays a larger role in hybrid search than previously thought. Specifically, to identify objects within the target category, WM resources may be deployed to compare the target set held in LTM to the potential target.

Contralateral delay activity is not a robust marker of cognitive function in older adults at risk of mild cognitive impairment.

Contralateral delay activity (CDA) has been proposed as a pre-clinical neural marker for mild cognitive impairment (MCI). However, existing evidence is limited to one study with a small sample size (n=24). Our aim was to extend previous work by investigating the relationship between the CDA and MCI risk in a large sample of older adults (n=76). We used a regression approach to determine whether (and when) CDA amplitude predicted MCI risk, as indexed by the Montreal Cognitive Assessment (MoCA). CDA amplitude from ~300-500 and ~800-900ms predicted MoCA performance. However, significant effects were only observed for specific electrodes (P5/P6 and CP3/CP4, but not PO7/PO8) and the nature of the relationship between the CDA and MoCA scores differed across time and according to set size. Bayesian regression analysis indicated partial evidence in favour of the null hypothesis (BF10 values=4-1.18). Contrary to previous results, our findings suggest that the CDA may not a robust marker of MCI risk. More broadly, our results highlight the difficulty in identifying at-risk individuals, particularly as MCI is a heterogeneous, unstable condition. Future research should prioritise longitudinal approaches in order to track the progression of the CDA and its association with cognitive decline in later life.

Electrophysiological correlates of the flexible allocation of visual working memory resources

Visual working memory is a brief, capacity-limited store of visual information that is involved in a large number of cognitive functions. To guide one’s behavior effectively, one must efficiently allocate these limited memory resources across memory items. Previous research has suggested that items are either stored in memory or completely blocked from memory access. However, recent behavioral work proposes that memory resources can be flexibly split across items based on their level of task importance. Here, we investigated the electrophysiological correlates of flexible resource allocation by manipulating the distribution of resources amongst systematically lateralized memory items. We examined the contralateral delay activity (CDA), a waveform typically associated with the number of items held in memory. Across three experiments, we found that, in addition to memory load, the CDA flexibly tracks memory resource allocation. This allocation occurred as early as attentional selection, as indicated by the N2pc. Additionally, CDA amplitude was better-described when fit with a continuous model predicted by load and resources together than when fit with either alone. Our findings show that electrophysiological markers of attentional selection and memory maintenance not only track memory load, but also the proportion of memory resources those items receive.

Electrophysiological evidence supports the role of sustained visuospatial attention in maintaining visual WM contents

Recent empirical and theoretical work suggests that there is a close relationship between visual working memory (WM) and visuospatial attention. Here, we investigated whether visuospatial attention was involved in maintaining object representations in visual WM. To this end, the alpha lateralization and contralateral delay activity (CDA) were analyzed as neural markers for visuospatial attention and visual WM storage, respectively. In the single-task condition, participants performed a grating change-detection task. To probe the role of visuospatial attention in maintaining WM contents, two color squares were presented above and below the fixation point during the retention interval, which remained visible until the detection display was present. In the dual-task condition, participants were required to maintain lateralized gratings while staring at the center-presented color squares, to detect possible subsequent color change. With this task, sustained visuospatial attention that guided to individual memory representations was disrupted. The behavioral data showed that, the insertion of secondary task significantly deteriorated WM performance. For electrophysiological data, we divided the retention interval into two stages, the early stage and late stage, bounded by the onset of the secondary task. We found that CDA amplitude was lower under the dual-task condition than the single-task condition during the late stage, but not the early stage, and the extent to which CDA reduced tracked the impaired memory performance at the individual level. Also, alpha lateralization only could be observed in the single-task condition of the late stage, and completely disappeared in the dual-task condition, indicating the disruption of visuospatial attention directed to memory representations. Individuals who experienced greater visuospatial attention disruption, as indicated by the alpha lateralization, had lower maintenance-associated neural activity (CDA), and suffered greater impairment of memory performance. These findings confirm that sustained visuospatial attention continues improving visual WM processing after the initial encoding phase, and most likely participates in this process by supporting the maintenance of representations in an active state.

Task goals modulate the activation of part-based versus object-based representations in visual working memory

ABSTRACTRepresentations of visual objects in working memory (WM) can be part-based or object-based, and we investigated whether this is determined by top-down control processes. Lateralised change detection tasks were employed where sample objects on one task-relevant side had to be memorized. Contralateral delay activity (CDA) components were measured during the retention period as electrophysiological markers of WM maintenance processes. In two critical task conditions, sample displays contained objects composed of two vertically aligned shapes. In the Parts task, test displays contained a single shape that had to be matched with either of the two sample shapes, encouraging the storage of part-based WM representations. In the Whole task, compound-shape objects shown at test had to be matched with memorized compound objects, which should facilitate the formation of object-based integrated WM representations. CDA amplitudes were significantly larger in the Parts task than in the Whole task, indicative of differences in effective WM load. This suggests that the two individual shapes were represented separately in the Parts task, whereas a single compound object was maintained in the Whole task. These results provide new evidence that changes in task goals can result in qualitative differences in the way that identical visual stimuli are represented in WM.

The Contralateral Delay Activity Tracks the Sequential Loading of Objects into Visual Working Memory, Unlike Lateralized Alpha Oscillations.

Visual working memory temporarily represents a continuous stream of task-relevant objects as we move through our environment performing tasks. Previous work has identified candidate neural mechanisms of visual working memory storage; however, we do not know which of these mechanisms enable the storage of objects as we sequentially encounter them in our environment. Here, we measured the contralateral delay activity (CDA) and lateralized alpha oscillations as human subjects were shown a series of objects that they needed to remember. The amplitude of CDA increased following the presentation of each to-be-remembered object, reaching asymptote at about three to four objects. In contrast, the concurrently measured lateralized alpha power remained constant with each additional object. Our results suggest that the CDA indexes the storage of objects in visual working memory, whereas lateralized alpha suppression indexes the focusing of attention on the to-be-remembered objects.

The neural correlations of spatial attention and working memory deficits in adults with ADHD.

Working memory impairment is a typical cognitive abnormality in patients with attention-deficit/hyperactivity disorder (ADHD) and is closely related to attention. Exploring the interaction between working memory and attention in patients with ADHD is of great significance for studying the pathological mechanism of this disease. In this study, electrophysiological markers of attention, posterior contralateral N2 (N2pc), and working memory, contralateral delay activity (CDA), were used to explore the relationship between these two cognitive abilities in patients with ADHD. EEG data were collected from adults with ADHD and age-, sex-, and IQ-matched normal controls while performing a classical visuospatial working memory task that consisted of low-load and high-load memory conditions. In different memory load conditions, the memory array elicited a smaller N2pc (220–260 ms) and a smaller CDA (400–800 ms) in adults with ADHD than in normal controls. Further analysis revealed that the reduced CDA amplitude could be significantly predicted by the earlier and reduced N2pc amplitude in adults with ADHD. Moreover, when the number of memory items increased, the increase in N2pc highly predicted the increases in CDA. Our findings illustrate the relationship between spatial working memory and attention ability in ADHD adults from the neurophysiological aspect that reduced working memory is closely related to insufficient attention ability and provide a potential physiological basis for the pathological mechanism of ADHD.

The capacity and resolution of spatial working memory and its role in the storage of non-spatial features

The question whether the storage of spatial locations and other non-spatial features in visual working memory (WM) is based on shared or separate processes remains unresolved. We recorded contralateral delay activity (CDA) components as on-line electrophysiological markers of WM maintenance in two tasks where observers had to retain either the colors or locations of sample stimuli. CDA components were elicited both in the Color and in the Location task, and increasing WM load had identical effects on CDA amplitudes, suggesting shared underlying mechanisms. However, CDA amplitudes were generally larger in the Location Task. Experiment 2 demonstrated that the CDA is sensitive to the resolution demands of spatial WM tasks. CDA amplitudes elicited during the storage of object locations in WM were larger when these locations had to be retained with higher precision. These findings support the hypothesis that spatial and non-spatial features of visual objects are represented in an integrated fashion in WM. The activation of these representations is controlled by space-based attentional control processes, and their spatial resolution can be regulated in line with current task demands.